JICABLE15_0001.docx Ampacity and other design considerations for medium voltage cables used in renewable energy applications Earle C. (Rusty) BASCOM, III (1), Richard W. ALLEN Jr. (2) 1 - Electrical Consulting Engineers, P.C., Schenectady, New York, USA, r.bascom@ec-engineers.com 2 - Consultant, Northboro, Massachusetts, USA, rwa01532@aol.com Renewable energy systems often include underground distribution cables to connect solar panels or wind turbines to collector stations where there is a step up in voltage for transmission to the nearest utility system. The general approach is to utilize medium voltage distribution cables. Many of these systems are designed and installed by developers that are seeking to minimize the project cost so that the payback period of the systems can be realized sooner, making the economics of these systems more attractive to regulators, utilities and other entities. There have been many instances of these cable systems failing after being placed in service due to issues related to thermal overload. The cause of these problems is based on applying traditional utility distribution cable system practices to the environments and operating scenarios associated with many of the renewable energy sites that have alternate characteristics. Factors to consider include: Common cable installation practices for renewable energy projects Geographic environments for renewable projects Route thermal survey and trench design and backfill characteristics Load and loss factors and circuit loading diversity as affects ratings Selection differences between utility distribution cables and renewable energy cables Economic factors Common project ownership Generating characteristics of wind and solar farms Cable system ampacity The combination of these factors and their proper consideration impacts longevity of the cable system and can result in rapid thermal degradation within a few years, affecting the availability and reliability of the renewable energy source that normally would have an expected life of decades. The paper summarizes and discusses each of these issues and shows that economic factors encourage minimizing the cable size for a given project while also seeking to reduce installation costs without fully engineering the cable ratings and design. Often, the assumed characteristics of the thermal environment are highly optimistically such that cable ratings based on the selected cable size are over stated. The paper identifies the key features of the cable system design to enhance reliability by avoiding thermal degradation of the cable system. The conclusion states that with careful selection of the cable size with proper consideration for the approach used during installation of the cable, including realistic evaluation of the extent of trench preparation and application of specialized backfill, can allow a reliable cable connection for renewable energy projects. The work is a guide to the renewable energy industry. JICABLE15_0002.docx New approach to installation of offshore wind energy cables Willem GRIFFIOEN (1), Christophe GUTBERLET (1), Jeannette MULDER-GROOTOONK (2), Lars HØJSGAARD (3), Willy GRATHWOHL (4), Håkan BRINGSELL (5), Johnny SØRENSEN (6), Niels-Jørgen BORCH-JENSEN (6) 1 - Plumettaz SA, Bex, Switzerland, willem.griffioen@plumettaz.com, christophe.gutberlet@plumettaz.com 2 - Wavin T&I, Dedemsvaart, Netherlands, jmulderg@wavin.com 3 - NKT Cables AS, Brøndby, Denmark, lars.hojsgaard@nktcables.com, 4 - NKT Cables AS, Asnaes, Denmark, willy.grathwohl@nktcables.com 5 - NKT Cables AB, Falun, Sweden, hakan.bringsel@nktcables.com 6 - Siemens Windpower, Brande, Denmark, johnny.soerensen@siemens.com, niels.borchjensen@siemens.com To reduce costs for subsea power cables in offshore wind applications, an alternative installation method has been developed. Instead of armoured cables HDPE pipes are laid (trenched) into the seabed. A special telescopic riser has been developed to install the pipes from the Transition Pieces (TPs), avoiding J-tubes. Specially designed bend restrictors bring the pipe into position in the seabed near the feet of the mono-piles. After that, the (non-armoured) cable can be installed into the pipe. For this the cable drum and (compact) installation equipment can be previously placed inside the TP. This system can with minor modifications be applied to other foundation types, e.g. gravity- and jacketfoundations. Cables are installed into the pipes using the water flowing technique, an alternative to traditional pulling. For cables used for offshore wind parks the technique has now been developed to work also without pig at the cable´s front-end (called floating). A high speed water flow propels the cable. Besides these propelling forces, a mechanical pusher introduces the cable into the pipe (which is under pressure), effectively pushing the cable. Because of the buoyancy of the cable in water, installation lengths are long while forces exerted on the cable are much lower than for traditional pulling, reducing wear. There is no need to first installing a winch rope. Also there is no need to place equipment at the far end of the pipe. The method can be used for installation of array cables as well as for export cables, the latter being even possible from land (current length of 3 km targeted to be increased to 5, 10, 20 km,...) Costs savings are achieved because of the lower price of non-armoured cable, reduced AC-losses and reduced risk of pipe kinking and thus eliminated risk to kink the cable (should the pipe kink, it is much easier to repair). Telescopic riser and flexible bending restrictor will allow the cable in pipe to follow the seabed in case of erosion around the mono-pile. Tests were performed which showed that non-armoured cables in pipes are better protected against mechanical impact than armoured cables, because of the free space in the pipe. Keeping the pipes in the TP-zone filled with water, hotspots will be better cooled. Trials done at Lindø, DK (onshore) and Thyborøn, DK (semi-offshore) are described. Here array cables (82 mm 3x300 mm2 Alu in 125/102 mm pipe) and export cables (60 mm 1x630 mm2 Alu in 90/80 mm pipe) were installed with ease over lengths of about 1 km, but the potential is much higher. Flexible joints were also tested to pass installation device and pipe. Using high salinity water the effective weight of the cable (in the pipe) can be tuned to zero. The same high salinity water can also be used to sink pipes. In many cases the density of the pipes with cable can even be tuned to the density of the seabed. Before the cables were installed, the pipe route was evaluated by intelligent pigging. JICABLE E15_0002.do ocx Fig. 1: Overview altern native system m Fig. 2: Overv view semi-offffshore trial JICABLE15_0003.doc The design of H level thermal -conductivity composite insulation structure for explosion-proof motor with high efficiency and low voltage LIU Chen-yang (1), YIN Mo (2), CHEN Xu-feng (3), ZHENG Xiao-quan (1) 1 - State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University,Xi an 710049,China; 2 - Nanyang Explosion Protection Group Co., Ltd., Nanyang 473011, China; 3 -.School of Mechanical Engineering, Shanghai Jiaotong University, Shanghai 200000,China Corresponding author, email: liucheyan@126.com When the electric motor is running for a long time, due to the rise of temperature of the copper wire effect, the electric motor winding temperature can be increased, and because of winding covered with insulating paint, that can make heat dissipation hardly and reduce the service life of the electric motor. In view of the difficult insulation structure heat dissipation problem, this paper developed a new type of high efficient heat conduction insulation structure(grade H) and the new method to reduce the motor temperature, made high thermal conductive insulation test and calculation analysis of efficiency for YB2132-5.5 Kw-4P electric motor. The result shows that the H level insulation structure can make the electric motor temperature reduce significantly, and it can also achieve the purpose of improving the efficiency of the electric motor. the H-class high thermal insulation structure tests for prototype losses, efficiency testing and theoretical analysis, calculated and experimental results show that the new high thermal insulation structure used to reduce winding temperature rise of 8 , the stator copper loss and rotor copper losses have been greatly reduced accordingly, improve the efficiency of the motor to reaches 86.7%, the efficiency of the existing motor is 0.7 percentage points compared to the initial motor, and the experimental and theoretical values are similar, it demonstrated the superiority of the design of thermal structure fully. Consolidation of the economic benefits generated by the use of the H high thermal insulation structure can save energy up to 44.8 million (yuan)/year for our country, it is a important implications for environmental protection and energy saving. JICABLE E15_0004.do ocx Perm manent PD P Mon nitoring Experiences on o Sha anghai 500kV 5 Powe er cable Lines JIANG yyun (1),GAO O Xiaoqing (1),QIAN ( T Tianyu (1),X XIAO Chuanq qiang (2),D DAI Hongbin (2) 1 - Shan nghai Electricc Power Com mpany, Shan ghai, China 2 - SIND DIA Instrumen nts, Beijing, China, xiao@ @sindia.cn For the safety opera ation of a 500kV 15.6 kkm-length po ower cable line, a permaanent PD monitoring m system w was installed d in Septemb ber 2013. Th he cable line included 2 circuits c and 6 phases in total, t with 159 HFCTs and PDDs were installeed on the grounding 147 cablle joints and d 12 GIS terrminations. 1 g cable of each joint an nd terminatio on. on installation n experience e and 1 yearr operating experience e of o the PD moonitoring sys stem, this Based o paper illustrates so ome key fac ctors for ca able line PD D monitoring g. These faactors includ de HFCT installatio on, calibratio on, alarm settting, and PD D pattern reco ognition. Differentt positions to o install HFCT sensors are comparred in this paper, p and H HFCT senso or on the groundin ng cable is recognized r as a the best sensitivity fo or PD monitoring. For jooint only with coaxial groundin ng cable ava ailable, it wa as recomme nded to insttall HFCT inside the crooss bonding box and modify th he box to ma ake the signa al cable out ffrom the box. Currentlyy no calibra ation standarrd is availab ble for PD measuremen m t based on HFCT meth hod. This paper re ecommends injecting PD P calibratio on signal directly into each HFCT T, measured d by the distribute ed system, to find out a relative ca alibration fac ctor, e.g. 4.9 9 was mosttly used in Shanghai S project. Alarm se etting was another a key issue in Sh anghai 500k kV cable line e PD monitooring, and th his paper recomme ends using 72 7 hours datta for alarm ccriteria. The alarm might be triggeredd by extreme e weather if time p period is too o short, or by the surfface discharrge of overh head line innsulators which were connecte ed to the ca able sealing g end. PD p pattern recog gnition was the most im mportant too ol for the judgmen nt of PD defe ect in cable line. The PD alarm of the e monitoring system wass only a callin ng for PD experts. Detailed ana alysis of the alarm signall was require ed by PD exp perts. With the e experience es of PD on n-line measu urement for cables, deffects in cabble insulation n can be measure ed in very wid de range of signal s freque ency, up to 20 MHz, depe ending on thee HFCT spec cification; defects iin cable oute er semicondu uctor might o only be meas sured in a lim mited signal fr frequency ran nge up to 3 MHz. T Therefore, ad djustment of the measure ement freque ency was very important for PD meas surement on cable e lines. This paper presents a method d to use both PD pattern n and freque ncy respons se pattern for judgm ment of PD defects d in cab ble. JICABLE E15_0005.do ocx Synta actic foa am as an a altern native electrica e al insula ation ma aterial for su upercon nducting g cable s systems s Daniel W WINKEL (1), Ralf PUFFER (1), Armin SCHNETTL LER (1),. 1 - RWT TH Aachen University, U Aa achen, Germ any, winkel@ @ifht.rwth-aa achen.de, pufffer@ifht.rwtthaache en.de, schne ettler@rwth-a aachen.de In superrconducting equipment for electrical power distribution netw works liquid nnitrogen (LN2) based insulation systems are commonly used. In n this case, liquid nitro ogen simultaaneously has s got an insulating and coolin ng function. One O disadva ntage of these insulation n systems is the bubble formation f within LN N2 due to he eat losses off the current carrying con nductor, whic ch reduces tthe dielectric c strength of the insulation system s dras stically. Furtthermore, th he significan nce of routiine tests performed p immedia ately after the production n of the com mponent is ra ather low wh hen LN2 is rreleased for delivery. Thus, th he tests are repeated on-site o after commission ning. An alte ernative to LLN2 based insulation systems are solid in nsulation sys stems where e LN2 has only got a co ooling and noo more an insulating i function.. Additionallyy, solid insula ation systemss can take mechanical m fu unctions. This pap per deals witth syntactic foam f as a so olid insulation n system, wh hich can be an alternativ ve to LN2 based insulation syystems for superconduccting powerr equipment. Syntactic foam consiists of a polymeriic matrix and d embedded hollow micrrospheres (H HMS) with mean m diameteers of severa al 10 µm. The emb bedded hollo ow microsph heres feature e a reduced d thermal co ontraction, a lower density and a lower re elative perm mittivity compared to th he pure ma atrix materia al. Several syntactic fo oams are investiga ated regardin ng their dielectric streng gth under AC stress, their thermal contraction and their mechaniical stability at liquid nitrrogen. For th his purpose, epoxy resin n (ER) and uunsaturated polyester resin (UPR) serve as a matrix materials of the e syntactic fo oam. The HMS used in this investig gation are made off glass and silanized gllass. By com mparing the results of measuremen m nts at liquid nitrogen temperature with tho ose at ambient tempera ature the influence of th he temperatuure differenc ce on the dielectricc strength ca an be determ mined. The resu ults show th hat the diele ectric strengtth decreases s with increasing filling degree and d the test temperature of 77°K K features hig gher dielectrric strengths than ambient temperatuure. Furtherm more, the dielectricc strength re eaches peak k values up to 53.9kV/m mm. Fig. 1 shows s the ddielectric stre engths of several ssyntactic foams based on n ER and UP PR with a filling degree off 50 percent of volume at ambient temperature (AT) an nd 77 K. Also the therma on is influenc ced by the ffilling degree e of HMS al contractio where hiigher filling degrees d lead to lower con ntractions. By y filling the polymer p matrrix with 50 pe ercentage of volum me with HMS S the therma al length con ntraction can n be reduced d to 0.5%. T The mechanical tests show tha at ER and syntactic s foam based on n ER induce young’s mo oduli of abouut 4000 MPa which is about ten times higher than the young’s y mod uli of UPR and a syntactic foam basedd on UPR. Th he results ed in the pa aper will sho ow syntactic foam as a promising alternative a innsulation ma aterial for presente supercon nducting cab bles and theirr accessoriess like termina ations. Fig g. 1:.Dielectriic strength of syntactic fo oam JICABLE15_0006.docx Estimating the impact of VLF Frequency on Effectiveness of VLF Withstand Diagnostics Nigel HAMPTON (1), Jean Carlos HERNANDEZ-MEJIA (2), Marina KUNTSEVICH (3), Joshua PERKEL (1), Vivek TOMER (3) 1 - NEETRAC, Atlanta, USA, nigel.hampton@neetrac.gatech.edu, josh.perkel@neetrac.gatech.edu 2 - Universidad de Los Andes, Mérida, Venezuela, hmjeanc@ula.ve 3 - Dow Chemical, Spring House, USA, kuntsem@dow.com, VTomer@dow.com Proof or withstand tests have been used for a very long time in the cable industry and find their origins in the well known routine tests carried out in accessory and cable factories. Experience shows that the most common voltage source used in service is the Very Low Frequency (VLF) approach. Although this test continues to serve the industry well and is described in detail in IEEE 400.2, when a Simple Withstand is implemented in the field users continue to raise concerns about the VLF frequencies: IEEE 400.2 discusses frequencies within the range 0.01 to 0.1 Hz. In most cases the need to move to lower frequencies is a result of needing to test longer (higher capacitance) lengths. One of the useful studies (Moh, CIRED 2003) has suggested that lower frequencies are correlated with a reduced survival probability (Failure On Test {FOT} plus Failure In Service {FIS}): 87% and 75% for 0.1 Hz and 0.05 / 0.02 Hz, respectively. It may be hypothesized that this was because the defects in the cable systems inherently had higher breakdown strengths when tested at the lower VLF frequencies. However, it has been conjectured that this finding may not be due to the frequency of test, but to the reduced strength of longer lines where there is a higher likelihood of weakened links (joints, terminations, and/or degraded portions of cable) being present: the longer the chain the more weak links! Furthermore the rates do not change between 0.05 to 0.02 Hz. The practical importance of any such difference in test frequency is that, if correct, there may be a need to extend the test time to compensate for the lower frequencies ie the concept of a minimum number of cycles. To provide further information on this topic studies are needed where the test frequency is varied independently of the system characteristic. Furthermore it would be advantageous to conduct such tests on test objects with a consistent level of degradation; the focus of this presentation. The study discussed in this presentation makes use of the well known Ashcraft Water Tree object to grow a series of Water Trees to a consistent range of lengths. These objects act as models for a degraded extruded cable. These objects are then subjected to VLF Withstand Tests at selected VLF frequencies (0.1 & 0.05 Hz). The electric stress at failure of these objects would provide an indication of the effectiveness of the selected frequency. This paper will describe Industry Background Test Protocol (Ashcraft Water Tree Growth (EPR, WTR XLPE, XLPE), VLF Test (sinusoidal)) Differences in breakdown strength (initial analyses) associated with the VLF Test Frequencies (Figure 1) The breakdown data suggest that, for degraded extruded insulations: The hypothesis that the breakdown strength is higher at lower VLF frequencies is not supported The proposal that the hypothesized higher VLF breakdown strength at lower frequencies requires an increase in the test time is not supported The inference is that testing at lower frequencies (often required for testing longer lengths) is no less effective than tests at the more common 0.1 Hz JICABLE15_0006.docx 99 90 80 Weibull Freq 0.05 0.10 70 60 50 Percent 40 30 20 10 5 3 2 1 4 5 6 7 8 9 10 Estimated Mean Breakdown Strength (kV/mm) Figure 1: Estimated VLF Breakdown Strength of Ashcraft Objects containing Water Trees (Water Tree Lengths 3% to 14% of insulation thickness) at selected VLF Frequencie JICABLE15_0007.docx Repeated field tests - Utility case studies of the value of trending Nigel HAMPTON (1), Jean Carlos HERNANDEZ-MEJIA (2), Joshua PERKEL (1) 1 - NEETRAC, Atlanta, USA, nigel.hampton@neetrac.gatech.edu, josh.perkel@neetrac.gatech.edu 2 - Universidad de Los Andes, Mérida, Venezuela, hmjeanc@ula.ve Papers and Standards often mentioned the benefits of establishing a baseline measurement and then following up with repeat tests spaced some reasonable time apart. They describe how this provides the best indication of the condition of a cable circuit. Although an admirable goal such repeat testing is rarely if ever undertaken. The primary reason is that resources are scarce and consequently it is difficult to complete the initial test program let along return in a reasonable period to repeat the tests. As there has been little in the way of “practice” to show the benefit of such an approach the authors decided to undertake such a study. Field tests have been performed on utility cable systems as part of the Cable Diagnostic Focused Initiative (CDFI) since 2006. In recent years (2010 to 2014), the authors have endeavoured to return to these circuits to repeat the same tests that were originally performed. The studies discussed in this paper make use of interpretation of the Dielectric Loss measured under VLF (Very Low Frequency) voltages. This paper will describe Recent Advances in the deployment of VLF techniques following the release of the updated IEEE400.2 Test Protocol in the field Determination of the Asset Health using a Diagnostic Based Health Index Changes in Asset Health Service Performance between tests Critical Utility decisions required to enable effective repeat tests in the future The results suggest that: The initial degradation and the change in degradation of the service performance is best described in terms of a robustly calculated Health Index rather than classification (good / not good) or the measured data (Tan Delta, Voltage Stability (Tip Up) etc) The rate of degradation is not constant within a population of uniform age The rate of degradation is higher in those units with poorer health The impact of remedial actions (partial replacement, accessory renewal, rejuvenation) can be observed JICABLE15_0008.doc The application of PD monitored AC voltage test in Beijing 500kV power cable lines acceptance AN Jianqiang (1), LI Zhen (1),DONG Yi (1),ZHU Zhanwei (1),SUN Changqing (1), XIAO Chuanqiang (2) 1 - Beijing Electric Power Company, Beijing, China 2 - SINDIA Instruments, Beijing, China, xiao@sindia.cn The paper introduces the acceptance test with 1.7 U0 in Beijing 500kV 6.7 km-length power cable lines. This was the first time in China to apply 493kV (1.7 U0) test voltage in 500kV long distance cable circuit. Four AC resonant HV systems were used with two in series and then two in parallel (Test equipments arrangement see as below), and reach test capability of output voltage 520kV, output current 166 A. The tests were performed in June 2014, with test voltage 493kV, test current up to 137 A, test frequency 35.4 Hz and test power 67.5 MVA. In order to combine the distributed PD measurement, test voltage tests were performed at the sequence of 0.5 U0 for 5 minutes, at the sequence of 1.0U0 for 10 minutes, at the sequence of 1.4 U0 for 10 minutes, and at the sequence of 1.7 U0 for 60 minutes. All three phases of the cable line passed the 1.7 U0 60 minutes voltage test. This test is considered influential to future HV cable acceptance test in China. A distributed PD monitored AC voltage test method is also introduced in this paper. Each phase of the cable line consist of 11 joints, 1 GIS termination and 1 outdoor termination. Therefore, 13 PDD units were installed and connected by fiber optical cables in a way of hand in hand. All PDD measurement signals were synchronized and measured by a computer located in the HV resonant system control room. Function check of the PD Monitoring system with 13 channels was performed by injecting 10 nC PD calibration signal from each termination. The attenuated signal was measured by each PDD installed on each joints along the cable line. Signal attenuation rate at 4 MHz should be no less than 93% per km. This regulation was used for the performance check of the distributed PD monitoring system. The technical requirements and on site PD system function check methods were introduced to find out that with HFCT methods, for PD signal injected from the outdoor sealing end, the PD signal amplitude was higher measuring from in joint number 1 than from the outdoor sealing end, but the signal frequency band is higher measuring from sealing end than from joint number 1. PD measurement criteria with no recognizable PD pattern were used for the first time in HV cable acceptance test in China. The importance of PD activity in quantity was minimized. PD signals generated by the HV connections were measured by the PD monitoring system, and no PD activity from cable and cable accessories was recognized in the test. JICABLE15_0009.docx Lillebælt - Installation and Commissioning of world’s first 400kV 3-core Submarine Cable Morten AHRENKIEL VILHELMSEN (1), Flemming KROGH (2) 1 - Energinet.dk, Fredericia, Denmark, mav@energinet.dk 2 - ABB, Karlskrona, Sweden, flemming.krogh@se.abb.com In this paper, the experiences of the design, production, installation and commissioning of the world’s first 400kV 3-core submarine cable are described. The Lillebælt project was based on a political agreement from 2009 which objective was visually to enhance the existing 400kV grid at a number of specified locations across Denmark. The scope of the Lillebælt project was to replace the two existing overhead lines crossing the Lillebælt Straight with underground and submarine cables. Through detailed project engineering including seabed surveys, soil investigations and intense dialogue with authorities it was determined that the optimal project layout required the cable to be subjected to: Crossing several roads Crossing nature protected commons and streams Up to 50 meter deep waters with significant currents in the highly trafficked Lillebælt Straight 1 km underground cable route through a golf course Crossing under a forest Safety issues due to parallel overhead lines Cable pulling in HDD’s The cable chosen to solve this scope was the ABB produced 400kV 3 x 1400 mm2 Al stainless steel armored submarine cable, the first of its kind on this voltage level. In addition to being the first ever 400kV 3-core cable, the cable is also the biggest power cable (dimension wise) in the world to date. Cable type testing according to IEC was performed on an experimental cable of similar design which ABB had produced prior to contract award In addition to the submarine cable also 33 km of 400kV single core underground cables for connecting the submarine cable to the remaining overhead lines were included in the project. The underground cables are connected to the overhead line using innovative new designs for the transition compounds. Installation of the underground cables showed to be challenging, mostly because the main part of the cable route was running in parallel with, and relatively close to, the 400kV overhead lines which the cables were to replace. A fault on these overhead lines could result in dangerously high induced voltage levels in the parallel cables during installation of cables, joints and terminations. A challenging part of the submarine cable installation was the installation of a Rigid Sea Joint on this world record cable. Due to all potential risks it was early decided to use the local Danish submarine cable installation contractor (J.D. Contractor) as they were familiar with both the location and installation of large size submarine cables. In general the installation went very well, mostly due to extensive planning. After installation of the two parallel circuits (submarine cable, underground cable and accessories), a Site Acceptance Test (SAT) was performed on both circuits in September 2013. After six hours of HVAC testing the world record cable system was ready for handing over from ABB to Energinet.dk. The two 400kV cable systems were commissioned in November and December 2013. JICABLE15_0010.doc Replacement of porcelain bushings with polymeric bushings in HV underground XLPE cable termination box Kim JAE SEUNG (1) Roh TAE HYUENG (1) Kim DONG KYU (1) Kim JIN (1) Kim YOUN CHAN (1) 1 - KEPCO Company, Yeongdongdaero Gangnam-gu, seoul Korea, kimjae@kepco.co.kr , danpung@kepco.co.kr, dongq@kepco.co.kr, jinyjiny@kepco.co.kr, chanchany@kepco.co.kr Nowadays, because of the NIMBY syndrome it has trouble in selecting the line route of the overhead transmission line. Further on the reason of its convenience in extension and maintenance, the underground transmission line has been increased. As the underground power system increases, we have endeavored much to secure the high technology of the grid operation and to prevent the cable failure in O&M. In the past, we applied the porcelain insulators type to XLPE termination box. Now, however, we have installed polymeric insulators type termination box since in 2004. This change was made mainly due to the high possibility of other facilities or lives damage from scattered porcelain by explosion (Secondary damages happened about 5 times). Moreover the polymeric type is lighter, and have the better dampproofing and stain-proofing compared to the polymeric type. Section Installed porcelain insulator Installed polymeric insulator Replacement insulator (polymer) Design KEPCO developed the polymeric insulator so that the only insulator would be replaced, instead of replacing the full set of termination box. This improves the cost-efficiency of the replacement of the terminal box dramatically. The developed polymeric insulator is now, in 2014, under the field test for checking its stability. KEPCO is planning to replace all porcelain insulators to polymeric type gradually. The polymeric insulator was tested in accordance with IEC international standard; Type test Tests on interfaces and connections of end fittings Tests on shed and housing material Bending test, tests on the tube material, Internal pressure test Check of the interface between end fittings and the housing, and so on As mentioned above, this paper will mainly present the necessity for the replacement of the porcelain insulator, construction methods for the polymeric insulator, and the result of its field test. KEYWORDS: porcelain insulator, polymeric insulator, replacement insulator, termination box JICABLE15_0011.doc The introduction of PD detection with On-Line PD diagnosis System in EHV underground power cable Kim JAE SEUNG (1) Roh TAE HYUENG (1) Kim DONG KYU (1), Kim JIN (1) Kim YOUN CHAN (1) 1 - KEPCO Company, Yeongdongdaero Gangnam-gu, seoul Korea, kimjae@kepco.co.kr, danpung@kepco.co.kr, dongq@kepco.co.kr, jinyjiny@kepco.co.kr, chanchany@kepco.co.kr KEPCO has installed on-line PD diagnosis system for both 154kV and 345kV cables since in 2011. The system is composed of HFCT Sensor, Antenna Sensor, Local and Master Station, and so on. By using the PD detection system, PD pulses were detected two times in the 345kV joint box and the PD detected joint boxes were replaced, prior to the fault occurrence. Through this PD detection system for EHV underground power cable, KEPCO is able to secure the stable power system and prevent the relevant failures in underground power cables. Date Detection of PD pulse and maintenance Photograph ▪ 345kV OOT/L (PJ type joint) 2014. √ J/B#7 A phase PD pulse(about 500pc) √ replace a joint box with new one As mentioned above, this paper will mainly present the example of the PD pulse detection, constituent of on-line PD diagnosis system and the installation conditions. KEYWORDS: On-line PD diagnosis system, PD pulse, Detection, Cable joint box JICABLE15_0012.doc On the way to compare the polarity reversal withstand capability of HVDC Mass-Impregnated and extruded cable systems. Massimo MARZINOTTO (1), Giovanni MAZZANTI (2), Uberto VERCELLOTTI (3), Heiko JAHN (4) 1 : Terna S.p.A., Viale Galbani 70, 00156 Roma, ITALY, massimo.marzinotto@terna.it 2 : Department of Electrical, Electronic and Information Engineering, University of Bologna, Viale Risorgimento 2, 40136 Bologna, ITALY, giovanni.mazzanti@unibo.it 3 : CESI S.p.A., Viale Rubattino 54, 20100 Milano, ITALY, uberto.vercellotti@cesi.it 4 : FGH Engineering & Test GmbH, Hallenweg 40, 68219 Mannheim, GERMANY, jahn@fgh-ma.com The reversal of voltage polarity is essential in HVDC cable systems with Current Source Converters (CSC), since it enables to revert the direction of the power flow. Mass Impregnated Non-Draining (MIND) cables are known to be able to withstand the voltage polarity reversal without particular problems. Such ability is assessed by performing a dedicated polarity reversal loading cycle test with voltage polarity reversals every 4 hours, according to Electra 189, 2000. Moreover, since long ago Terna S.p.A., the Italian Transmission System Operator, has introduced in its test protocols for HVDC MIND-insulated cable systems the so-called “sustained polarity reversal loading cycle test”. This test has proved to be very effective for a thorough assessment of the cable system performances in the presence of polarity reversal during cable tests of different HVDC interties. On the other contrary, HVDC cables with extruded insulation are known to suffer the voltage polarity reversal by much, and this unsatisfactory behavior has hampered the development of HVDC-CSC extruded cable systems, with one single realization worldwide to date. As discussed broadly in the literature, the problems for HVDC extruded cable systems under voltage polarity reversal arise from the space charge that is accumulated in the extruded insulation. However, the latest research and development led some manufacturers to develop HVDC extruded cable systems that are claimed to be capable to withstand polarity reversal. Since the experience is quite scarce, voltage polarity reversal loading cycle tests capable to compare the performances of extruded cables and accessories in the presence of polarity reversal with the known behavior of MIND cables and accessories are required. This paper describes a broad and thorough test campaign that aims at this goal. The campaign is based on a joint partnership between CESI, Terna and a few major cable manufacturers in the world, and is planned to be carried out in the near future in the new HVDC test labs of CESI in Mannheim, Germany. This test campaign has been planned by deriving the voltage levels and duration of the various stages of the tests on the one hand from the experience gained by Terna in testing MIND cables, and on the other hand on dedicated aging and life models developed for extruded cables in cooperation with the University of Bologna, Italy. Key words Current Source Converters; Extruded insulation; HVDC cables; Loading cycle tests; MIND insulation; Voltage polarity reversal JICABLE15_0013.docx Computationally light two-zone moisture migration modelling for underground cables - critical temperature vs. critical heat flux Robert John MILLAR (1), Merkebu DEGEFA (1), Matti LEHTONEN (1) 1 - Aalto University, Espoo, Finland, john.millar@aalto.fi, merkebu.degefa@aalto.fi , matti.lehtonen@aalto.fi Underground cable installations in porous backfill material can experience moisture migration, the movement of moisture away from a heat source, which can severely limit the load transfer capacity of the system. There has long been discussion about whether a critical temperature rise or heat flux is the most important driver for moisture migration when modelling the thermal environment in terms of an equivalent two-zone separation of moist from dry conditions, for which references will be given. Full solution of the equations that model the coupled water and vapour transport mechanisms in porous media subject to temperature and hydraulic gradients, usually utilising the Philips and de Vries equations, have been accomplished by research groups that will be duly referenced in the full paper. Although such detailed analyses tend to remove the dilemma between critical temperature rise vs. heat flux, there is still room for methodologies that are computationally light for real time temperature prediction based on current measurements and a thermally relevant modelling of the cables in their thermal environment. The authors have previously developed real-time two-zone methodology based on a critical radius rx that corresponds to a critical temperature rise that delineates dry from moist. This paper presents a formulation that defines the critical radius in terms of a critical heat flux (that itself can have moisture and temperature dependence for a given backfill) and imbeds it in an existing cable temperature prediction algorithm. Although the algorithmic context of the new development will be briefly outlined in this paper, it is fully expounded in previous work by the authors. The methodology utilises hypothetical steady state target conditions to which the response at every time increment tends. The steady-state equation for the solution for the critical radius in terms of the critical heat flux, qx is: rx qx i o dry r0 dry wet i o r qx W0 i wet qx ro dry wet dry , (1) where i, ri, o and ro are the temperatures and radii at the inner and outer nodes (between which the critical heat flux occurs) of the equivalent thermal circuit that models both the cables and their installed environment. W0(x) is a special (real) solution of the Lambert W function, which is approximated by a polynomial expression in the algorithm, and wet and dry are the thermal resistivities (K m / W) of the moist and dry regions. Equation (1) with its derivation and the previous solution in terms of critical temperature rise will be compared, seeing which method comes closest to predicting the measured temperatures of a cablescale heating tube installed in graded sand backfill at Aalto University, subject to a time-varying load profile that causes moisture migration. JICABLE15_0014.doc Rating of HVDC submarine cable crossings Ziyi HUANG (1), James A PILGRIM (1), Paul L LEWIN (1), Steve SWINGLER (1), G TZEMIS (2) 1 - University of Southampton, Southampton, UK, zh2g09@soton.ac.uk 2 - National Grid Plc, Warwick, UK, Gregory.Tzemis@nationalgrid.com With the construction of a European wide super grid, long-distance bulk power transmission is planned between maritime nations through high voltage dc (HVDC) submarine cable circuits. As the cable route is normally constrained due to bathymetric conditions, fishing activities, etc., submarine cable crossings can occur in various occasions. Unlike the directly buried land cable crossing, the submarine cable crossing normally requires extra protection measures (e.g. rock berm, concrete mattress installation) to resist seabed activities such as scouring. Therefore, the thermal environment is significantly different after the crossing installation, which may affect the thermal rating of both crossing circuits. At present, the analytical crossing rating calculation (IEC60287-3-3) is inapplicable for submarine crossing ratings because the key assumption of an isothermal ground surface (i.e. to satisfy the use of ‘image’ theory) does not hold under a rock berm installation. Therefore, the numerical FEA modelling becomes the only alternative to approach this problem. More specifically, FEA provides a more reasonable and accurate solution, by removing the idealistic assumptions in the IEC method. For instance, ‘hybrid’ heat transfer (conduction, convection) within rock berm pores can be calculated and arbitrary protection layer structures can be examined. In summary, this work has shown through FEA modelling that the lower circuit is normally pushed over its thermal limit in a crossing, while the upper circuit can still operate safely with its original standalone rating. However, the reason for an escalated temperature in the lower circuit is often the overall protection layer installed above, but not the upper circuit. This paper will analyse the thermal implications of using a variety of different crossing designs. Various rating combinations are examined and practical implications are presented. It is believed that this work provides a useful preliminary study on HVDC submarine cable crossing ratings, which can be beneficial for cable system operators. Illustration of 3D cable crossing installation and longitudinal temperature distribution JICABLE E15_0015.do oc HVDC C cable e rating g metho odology y: therm mal, ele ectrical,, and mech hanical constra c ints Ziyi HUA ANG (1), Jam mes A PILGR RIM (1), Paull L LEWIN (1 1), Steve SW WINGLER (1)), G TZEMIS S (2) 1 - Unive ersity of Soutthampton, Southampton,, UK, zh2g09 9@soton.ac.uk 2 - Natio onal Grid Plc, Warwick, UK, U Gregory.T Tzemis@nattionalgrid.com m With the e continuing growth in energy e consu umption worrldwide, the move towarrds a Europe ean wide super grrid will result in significan nt changes in n how modern transmiss sion and disttribution netw works are operated d. As long-distance bulk power transsmission betw ween maritim me nations iss normally ca arried out through high voltage e dc (HVDC) power cab ble circuits, fundamental f to this is thhe need to accurately a know or determine their available ampacity. Therefore, an a accurate cable rating becomes pa aramount towards an efficient and a safe ope eration of tran nsmission ne etworks. Besides the standarrd IEC therm mal-limited ra ating methodology which follows a maximum conductor c temperature constra aint to preve ent excessivve dielectric thermal age eing, HVDC applications s impose extra ph hysical constraints (i.e. electrical and d mechanical) on the cab ble rating annd are not th horoughly considerred by stand dard rating approaches.. Electrically y, the dielec ctric field invversion unde er HVDC applications has its maximum electrical strress at the insulation screen, s whicch increases s with an increasin ng current lo oading. This means a die electric electrrical breakdo own may occcur before th he normal upper th hermal limit is exceede ed. Thus a rating meth hodology limited by the maximum dielectric electrica al stress is very v useful. Mechanicallly, unaccep ptably high interfacial prressure changes are reported during loa ading cycles through th hermal expansion or co ontraction. C Consequently y, plastic deformation of the ca able sheath can c occur an nd dielectric voids might be introduceed. Therefore e, a rating methodo ology which prevents in nternal mech hanical dam mage is also o of great vvalue. Therm mally, the analytica al calculation n loses its applicability a ffor submarin ne cable cro ossing ratinggs as some idealistic assumpttion no long ger holds (e.g. ( isotherrmal ground d surface). Therefore, numerical modelling m techniqu ues become preferable for thermall rating calc culations es specially in complicated d thermal environm ments. This pap per will firstlyy explain, in a comprehen nsive manne er, the new rating r methoddology developments by the a author to add dress these challenges. c S Subsequently, applicatio ons of a propposed modern HVDC nstrated. It is believed that this workk provides an cable rating methodology system m are demon a overall e for rating HVDC H cables s with approp priate metho odology, whic ch can be beeneficial to both cable guideline manufaccturers and utilities. u Therm mal rating vs Electrical E stres ss-limited ratin ng The ermal rating vs s Mechanical pressure-limitted rating JICABLE15_0016.docx The need to update / upgrade test procedures for connectors used in MV underground joints Barry FAIRLEY, Nigel HAMPTON, Thomas PARKER 1 - NEETRAC, Atlanta, USA, barry.fairley@neetrac.gatech.edu, nigel.hampton@neetrac.gatech.edu, thomas.parker@neetrac.gatech.edu Although cable systems are rated for operation at temperatures in the range of 90 to 105°C, the vast majority operate at temperatures much lower than this (in the range 35 to 45°C). Consequently reports of problems / failures with overheating connectors are very rare. However the authors have noted that overheating problems are more regularly being reported when the cable systems are operated above the normal 30 to 45°C range, yet puzzlingly below the rated temperatures. The causes of this phenomenon were not clear though a number of hypotheses are being discussed. Consequently, it was decided to conduct a number of designed experiments to try and bring some clarity to this issue. The testing, patterned on the load cycle test of IEEE Standard 404, was undertaken on a range of cases with a large number of replicates and provided a good level of confidence. The results indicated that, contrary to expectation, the connector inside many medium voltage (MV) underground cable joints will overheat when the current is increased to achieve a cable conductor temperature of 90°C, the rated temperature for typical cable systems. This implies that there is an increased risk that those cable joints may fail prematurely in the field if they are loaded up to or near their design rating. The IEEE 404 test program is designed for the qualification of the dielectric system of cable joints. It obliquely addresses the current carrying capability of connectors by requiring that connectors used for medium voltage underground cable joints be qualified using the ANSI C119.4 test protocol. The ANSI standard is widely used to evaluate connectors in the overhead environment and tests the connector bare (without the splice housing). Available data from the tests conducted by the authors indicates that the ANSI protocol is likely not adequate for evaluating the performance of connectors installed in MV joint housings. Data was gathered in such a way that it was possible to compare the thermal performance (temperature achieved and the temperature stability) of connectors in tests patterned after the IEEE 404 load cycle test protocol with the results of the ANSI C119.4 Current Cycle Submersion Test (CCST). The results showed: Very different temperature performances between the approaches The temperatures achieved by connectors at quite moderate conductor temperatures are likely to have very deleterious consequences for the components of joints The ranking of connector thermal performance seen in the full scale tests did not match that of the ANSII test This paper will describe Industry Background Experimental Design (Connectors, Dies, Joint Technologies, Sizes) Equilibrium temperatures achieved for selected cable conductor temperatures Effects that may be ascribed to the experimental factors Attempts to reconcile ANSI C119.4 results with those of practical cable joints Nonlinearities observed and the challenges of a thermal modeling approach Implications for infrared (IR) monitoring programs Potential for the development of an improved test protocol JICABLE15_0016.docx The data suggest that, for the cable accessories currently being installed: Most connectors (>90%) will operate at temperatures higher than the cable conductor The positive delta between connector and conductor temperatures does not lead to significant performance issues for cable conductor temperatures below 70 to 80°C (Figure 2) Continual operation close to or above 90°C is likely to result in quite large (>15°C) temperature deltas The expedient approach of using the ANSI tests for overhead connectors to demonstrate that connectors may perform well for MV cable joints (data would be expected to fall upon the diagonal line in Figure 3) is very likely not robust - see variations in connector rank for installations i, VI, IX {XI shows best performance [lowest temperature] within the application but is non compliant in the simple ANSI test} and inconsistent compliance i & ii, iii & iv, V & VI There does not appear to be a practical way by which the ANSI C119.4 criteria (compliant / non compliant) can be made to correlate with the real connector thermal performance seen in the IEEE 404 style load cycle tests, which better represent how the connectors are used The use of models of the cable accessory to qualify connectors in cable joints is believed to be practical and attractive as it provides information on the particular architecture of interest 200 Compliant i VI VII VIII iii 175 Temperature (C) 125 100 90 75 Ranked ANSI Performance Non_Compliant 150 Non_Compliant 50 40 Max @ 40° Max @ 90° Figure 2: Maximum temperatures achieved by connectors inside joints for selected conductor temperatures (40°C and 90°C on x axis) in a Box and Whisker format iv IX V ii X Numerals reflect different groups of connector installation methods Highest_Poorest Lowest_Best Ranked IEEE 404 Performance based on Temperature Figure 3: Correlation of rank order from IEEE 404 style and ANSI tests - the diagonal line indicates good agreement between the ranks JICABLE15_0017.docx Decision making & forecasting using the data available to utilities - Pitfalls, challenges and case studies of ways forward Detlef WALD (1), Joshua PERKEL (2), Nigel HAMPTON (2), 1 - Eifelkabel, Villmergen, Switzerland, d.wald@ieee.org 2 - NEETRAC, Atlanta, USA, nigel.hampton@neetrac.gatech.edu, josh.perkel@neetrac.gatech.edu The interest in Asset Management for Cable Systems continues to grow. There are many goals, but the most common are to a) wisely use the resources allocated to Operations and Maintenance and b) predict how these resources will need to grow with time as the system continues to age at a rate which is likely to be modified by the remedial actions. Perhaps the key challenge is to develop the baseline models which realistically estimate the future under the “status quo” operation. In principle, this should be straightforward as all that is required for such estimates are the installation and failure records for the cable system. However, it is the acquisition of these simplest of data that has always been the challenge for people working in this area; as it is often reported that the data are limited, incomplete, and/or inconsistent. As a consequence simple “rules of thumb” (linear approximations of failure rates) / heuristics (age based conditioning) are often used in the base case models; with all the inherent in accuracies in these approaches. Clearly the heuristic approach poses a major hurdle for Asset Management programs which aim to develop a consistent and transferable approach to estimating the value of various intervention strategies. The uncertainty inherent in the base case makes it difficult to determine the optimal strategy either in terms of effectiveness of efficient use of limited resources. Furthermore, the magnitude or direction (smaller / larger) of the base case uncertainty is not known. Cable System Diagnostics show great promise in guiding Asset Management programs that require immediate feedback. However they have not thus far provided assistance in the arena of predictions. Recent evolutions in the technology have led to the use of Data Driven Health Indices which provide a robust snap shot of current condition and indications of ageing dynamics via Age Lines. Unfortunately, diagnostics are not completely perfect for this application as they are not retroactive, require investment in data collection / collation and are inherently “sampling-based” as it is not possible to test every circuit. Historical utility data has always been attractive because it is available now, all encompassing (not sample based), segregated (age / type etc) and completely historical thereby including all the transients / changes that have occurred on the system. Its use has been limited due to the concerns of data fidelity / changing data management systems / dispersed storage. However, there have been some recent developments by which the data may be “cleaned” and “re assembled” in a practical and expedient manner. As a consequence much more of this type of analysis may be undertaken. Thus there are attractions and drawbacks with both of the approaches available to utilities. This paper will discuss these issues further and provide illustrations via Case Studies; thereby describing: Newly developed algorithms for Diagnostic Data that provide pre conditioning for use in Asset Management Analyses Architecture of utility service data and why this makes “classical” analysis difficult Data fidelity issues that compound the challenges of the architecture Distribution fitting solutions for discrete devices (Parametric Modeling with assumed Failure Sequence) Trend evaluation and prediction for lumped failure per year data (Crow AMSAA) Modeling using pre treated utility data (Parametric Modeling with Population Reconstruction) Indications of how they might be included in “value” case studies Dielectric Loss tests establishing system health with prognosis of future service performance under different remediation strategies Service Failure Data estimating Survival Curves for different cable system technologies and vintages, thereby providing guidance on the optimal intervention strategies JICABLE15_0018.doc Review of underground cable impedance and admittance formulas Akihiro AMETANI (1), Isabel LAFAIA (1), Jean MAHSEREDJIAN (1) and Antoine NAUD (2) 1 -Polytechnique Montreal, Montreal, Canada, aametani@doshisha.ac.jp, isa31188@gmail.com, jean.mahseredjian@polymtl.ca 2 - Reseau de Transport d’Electricite (RTE), Paris, France, antoine.naud@rte-france.com A number of underground cable transmission systems are under construction and/or are planned in many countries, and active investigations related to the cables have been carried out by CIGRE WG B1.30 and WG C4.502 an reported in CIGRE Technical Brochures. For the insulation design and coordination of an underground cable, it is essential to predict and investigate possible over-voltages in the cable system. Cable impedance and admittance formulas are necessary to study transient and steady-state phenomena on the cable. The impedance and admittance formulation of a cable is far more complicated than that of an overhead line, because even a single-phase cable consists at least of two conductors, i.e. a core conductor and a metallic sheath (shield) in the case of a single-core coaxial cable (SC cable). Also a long high-voltage SC cable is quite often cross-bonded, similarly to overhead line transposition. Furthermore, a so-called pipe-type cable (PT cable), such as a POF cable, is composed of threephase cores installed within a conducting pipe. Then the PT cable becomes a four-conductor system. If the inner conductors are SC cables, the PT cable is a seven-conductor system. An impedance formula of a cylindrical conductor was derived by Scheluknoff in 1932. The impedance and admittance formulas of an SC cable were developed by Wedepohl and Wilcox. The impedance and admittance formulas of a PT cable, where an inner conductor is eccentric to the pipe centre, were developed by Brown and Rocamora. The earth-return impedance of an underground cable was derived by Pollaczek. This paper summarizes the impedance and admittance formulation of three-phase SC and PT cables implemented into the EMTP (Electro-Magnetic Transients Program) as a subroutine “Cable Constants” since 1976 in the Bonneville Power Administration, US Department of Energy. Modeling of various cable systems such as cross-bonded and tunnel-installed cables is also explained. Problems related to the formulation and the impedance formulas have been reviewed, and possible countermeasures are described. Some of the problems come from approximations adopted in the formulation and assumptions made to derive the impedance formulas. Numerical electromagnetic analysis tools such as NEC (Method of Moments - MoM) and VSTL (Finite Difference Time Domain - FDTD) are explained as a solution for the problems reported in this paper. However, these methods require large memory and CPU time, and their accuracy is heavily dependent on memory size, time step, segment length (in NEC) and cell size (VSTL). JICABLE15_0019.docx Boutre-Trans Project: 225kV AC underground cable installed in the South-East of France Isabel LAFAIA (1), Akihiro AMETANI (1), Jean MAHSEREDJIAN (1), Antoine NAUD (2), Maria Teresa CORREIA de BARROS (3) 1 - Polytechnique Montréal, 2900 boul. Édouard-Montpetit, Québec, Canada 2 - Réseau de Transport d'Électricité, Cœur Defénce-100 esplanade du Général de Gaulle, 92932 Paris La Défense Codex, France 3 - Instituto Superior Técnico, Universidade de Lisboa, Avenida Rovisco Pais 1, 1049-001 Lisboa, Portugal By the end of 2014, RTE (Réseau de Transport d’Électricité, company responsible for the electricity transmission in France) will be commissioning the 225kV AC underground cable Boutre-Trans in the south-east of France. With a length of 65 km, this is the longest underground link for such a high voltage level. In order to validate the cable model for transient studies RTE has performed field measurements and has established a partnership with Polytechnique Montreal to build and validate the cable model based on those results. This paper presents the Boutre-Trans project including the field measurements and the first attempt to simulate the cable system in electromagnetic transients simulation tool (EMTP-RV). Being installed in HDPE tubes, the air gap and tube will influence the propagation of intersheath modes on the cable. The cable outer insulator, air gap and HDPE tube form a multi-layer eccentric outer insulator which cannot be handled by the present Cable Constants in EMTP-RV. This paper presents an equivalent insulator model that allows considering the HDPE tube in an EMTP-RV simulation. The semiconducting layers screening core and insulator in Boutre-Trans cable influence the propagation of coaxial modes and are included in the calculation of series impedance and shunt admittance matrices. The grounding system (grounding rods used for impulse generator, oscilloscopes and metallic sheaths) affects the measured voltages and is thus included in the EMTP-RV simulations. The simulation results using the EMTP-RV cable model are compared with measurement results. JICABLE15_0020.doc Development of a up to 400kV XLPE Cable with Low-Smoke Properties to be Installed in a Tunnel Feyzullah ATAY (1), Ismet CIHAN (2), Detlef WALD (3), Paul WILLIAMS (4) 1 - Demirer Kablo, Istanbul, Turkey, f.atay@masscablo.com 2 - Demirer Kablo, Istanbul, Turkey, I.cihan@masscablo.com 3 - Eifelkabel, Villmergen, Switzerland, d.wald@ieee.org 4 - UK Power Networks, Crawley, UK, paul.williams@ukpowernetworks.co.uk Recent experience shows that more and more high (HV) and extra high voltage (EHV) cables are installed either in tunnels or in sensitive areas where flame and smoke performance may become an issue should the cable be impacted by a fire during its operational lifetime. During a fire these cables will normally be switched off. However, they should not contribute to the fuel load in the event of an external fire. If they are involved in a fire they should act in a neutral manner and not contribute hazardous gases and energy to it. The move from self contained fluid filled cables to solid dielectrics has already reduced the fire risks of HV and EHV power transmission within tunnels. Nevertheless the materials (insulation and jacket) used in an extruded cables are still to some extent flammable. The traditional use of poly vinyl chloride (PVC) as a fire performance jacketing is becoming less practical for several reason such as creation of dense obscuring black smoke and the liberation of toxic products that are deleterious to humans and machinery. This is in addition to the well known limitations of PVC in terms of water transmission and sensitivity to abrasion and impact. After our first development of a 500kV cable system we have tested several solutions to the complex problem of providing both fire and mechanical protection of cables. These performances were compared with our desire to achieve a cable with low-smoke properties that could be installed in both tunnels and also directly in the ground. Investigations were made to check not only the obvious influence of different sheathing materials, but also the inherent blend to blend variations in the jacket materials. The tests were carried out according to IEC 61034. Reflect upon some of the deficiencies observed in the practices advocated within the standard. These will include correction factor for the smoke density for big cables, augmentation to address larger cables rather the more common small diameter cables. It proved very beneficial to make use of IEC 60332-3 to check the fire propagation of these cables. This was not immediately apparent as this standard designed for the installation cable and not for HV and EHV cables. It is interesting to note that since there was no widely accepted international standard available it is quite common to find this approach used by utilities and customers. In this paper we will: Describe the test procedure Analyse the results on a number of cable system designs Provide input on 1. difference between various metal sheaths 2. different materials 3. lot to lot variation of the same material Describe the issues of water absorption of these sheathing materials in the direct buried application If accepted the authors would like to have oral presentation in section 8 or 4 JICABLE15_0021.doc Development of an alternative solution to mica tape for fire resistant cables Detlef WALD (1), Harry ORTON (2), Jimmy DI (3) 1 - Eifelkabel, Villmergen, Switzerland, d.wald@ieee.org 2 - Orton Consulting Engineers International , North Vancouver, Canada, h.orton.1966@ieee.org 3 - Volsun Electronics, Suzhou, PR China. JimmyVolsun@gmail.com Until recently fire resistant cables used mica tapes as the fire resistant insulation material. The problem with this design was that mica tapes were very brittle and may break during normal handling of these cables. Therefore to improve the mechanical properties a small polymeric layer was extruded over these tapes. Recent developments have taken place that include the combination of these two layers into the one tape and the removal of the extrusion process covering the mica tapes. This paper will demonstrate, with examples, the advantages of these tapes as compared to the conventional construction using mica tapes in terms of: Ease of handling Improved mechanical properties No mechanical damage of the screen during handling and Improved fire performance. Currently these tapes are mainly used for low voltage cable applications, but tests are ongoing to use these tapes for medium and even low, high voltage cable applications where fire performance is required. Fig. 1: Picture of a small cable sample undergoing fire testing JICABLE E15_0022.do ocx Expanding the perfo ormance e of on site tes sting wiith frequ uency tuned d resona ant test system ms Sadettin ERDENIZ (1), Kemal GÜ ÜRSOY (1), Peter MOHA AUPT (2), To oni GEIGER (2) 1 - EMELEC Electriccal Engineering &Trading g PLC, Istanb bul, Turkey, sadetttin.erdeniz@ @emelec.com m.tr, kemal.g ursoy@eme elec.com.tr 2 - Moha aupt High Vo oltage, Miede ers, Austria, peterr.mohaupt@m mohaupt-hv.com, toni.ge eiger@mohau upt-hv.com The benefit and nece essity of afte er laying testss of long HV and EHV ca able line becoomes more and a more obvious. Still today providing an n easy to tra ansport, setu up and use test voltage source is ambitious. a Especiallly in case off long lengths and HV orr EHV cable systems the e usual equippment gets bulky b and logistically challengin ng. Also the setup s time a nd effort for the installatio on on site m ight be difficult. per introduce es the new trend t to use e a frequenc cy tuned reso onant test syystem opera ating at a This pap frequenccy of the test voltage of o 10 Hz. Th his approach h enables either e much more light weighted equipme ent or the po ossibility of te esting much h longer leng gths compare ed to existingg testing solutions of same typ pe. Fig. 1: F Frequency Tu uned resonan nt Test Syste em, 350kV, 10A, 1 10 Hz fo or On Site Caable Testing g This tren nd is driven n by the nee ed for testin ng ultra long g cables leng gths such aas submarine e cables. Thereforre CIGRE tecchnical broch hure TB490 proposes an n extended frrequency rannge down to 10 Hz for routine a and after insttallation tests s of long AC submarine cables. c The equ uipment in usse comprises a 10” con tainer mounted feeder system s and a setup of 4 air core reactors of extreme high h quality factor. f The to otal setup (see Fig. 1) offers up to 3550kV at 10A or 175kV at 20A. With this ra ating, testing g cables up to nearly 2μF 2 (equals approx. 10 km) on a 17t 1 trailer becomess possible. The outlines of the te est equipmen nt, its practiccability and first onsite experience aree described. JICABLE15_0023.doc Performance optimization of underground power cables using real-time-thermal-rating Martin OLSCHEWSKI and Wieland HILL 1 - LIOS Technology, Schanzenstrasse 39, Building D9-D13, 51063 Cologne, Germany Martin.Olschewski@lios-tech.com, Wieland.Hill@lios-tech.com Temperature monitoring is the key factor for the optimization of underground power transmission lines, because the ampacity of insulated power cables is limited by the maximum temperature of the conductor that does not affect the insulation material. Cable design, bonding, laying scheme, neighboring cables, other heat sources, thermal resistivity of soil, ambient temperature, load history are the most significant factors that have important impact on the conductor temperature. The calculation of the conductor temperature even under cyclic load conditions demands for efficient algorithms and still remains a current research topic. Distributed temperature sensing (DTS) is a powerful tool to monitor the temperature of the screen or at the sheath along the power cable. Depending on the load situation and surrounding parameters the temperature difference between screen or sheath temperature is not fixed. Real-time thermal rating (RTTR) is the method of choice for the calculation of the conductor temperature and for the capacity prediction. We have developed a fully integrated DTS/RTTR system with rating algorithms optimized for making full use of the DTS information and for fast real-time calculations. The RTTR engine uses the following main processes to evaluate the state and ampacity of the power cable: - Calculation of conductor temperatures along the full length of the cable Identification of critical locations and triggering of (pre-)alarms based on conductor temperatures Fitting of soil and ambient parameters to match the temperature and load histories Prediction of ampacity, conductor temperature or time for different load scenarios Evaluation of the accuracy of the predictions. If the DTS fibre is in the screen or attached to the power cable, the conductor temperature can be calculated by using the DTS temperature readings, the current history and the cable design data. Everything outside the fiber can be neglected. This makes the calculations fast enough to determine the conductor temperatures for all points along the cable in real-time. It also enhances the accuracy of those calculations because they are not affected by less precisely known environmental parameters such as thermal resistivity of soil and ambient temperature. We verify the accuracy of each model used in conductor temperature calculations by comparisons with finite element method (FEM) simulations. Since future DTS readings are not known, full thermal models of the complete laying scheme have to be used in ampacity predictions. Those models include environmental parameters such as soil thermal resistivity and ambient temperature that can vary considerably with the seasons. We determine the environmental parameters in real-time by fitting them to the temperature and load histories of the cable. We also use a newly developed multilayer RC-ladder soil model [1] to avoid the approximations used in the IEC standards. Predictions for ampacity, temperature and time can be calculated for constant load and also for custom load profiles. Finally, the accuracy of predictions can be validated by comparing predictions from the past with conductor temperature calculations. All DTS readings from multiple instruments, conductor temperature profiles and prediction results are stored together in a modern SQL database. Powerful visualization tools enable multiscreen visualization of temperature profiles and histories, current data as well as intuitive, custom visualization of all data on maps, pictures or drawings of the full power cable installation. JICABLE15_0023.doc [1] M. Diaz-Aguilo, F. de León, S. Jazebi, and M. Terracciano, IEEE Trans. Power Deliv, 2014 Key words Real-Time-Thermal-Rating, Distributed-Temperature-Sensing, power cable monitoring, integrated DTS/RTTR system JICABLE15_0024.doc 28 A novel lumped L-C ladder method for computing switching overvoltages in EHV long shunt-compensated cables Roberto BENATO (1), Sebastian DAMBONE SESSA (1), Davide PIETRIBIASI (2) 1: Department of Industrial Engineering, University of Padova, Via Gradenigo, 6/A, 35131 Padova, Italy (e-mail: roberto.benato@unipd.it, sebastian.dambonesessa@unipd.it ) 2: Prysmian Power Link, Milan (e-mail: davide.pietribiasi@prysmian.com ) The Laplace domain is a well-known tool in order to study circuit transients. When dealing with power transmission lines with uniformly distributed parameters the usual transmission matrix or ABCD matrix can be also written in Laplace domain. This involves voltage and current dependence upon spatial and temporal independent variables. In case of an insulated cable line (ICL) energization, the voltage at no-load end represents one of the most important switching overvoltages. Therefore the possibility of having a reliable, simple, fast and self-implemented tool to determine the transient behaviour ICL energization can be important for power engineers. ATP/EMTP-RV or other software are suitable and commercially-available tools in order to analyse transients in power systems. Notwithstanding, academia has always aimed at finding alternative tools which include self implementation in mathematical software environment. One of the most powerful tools for transient analysis is the Laplace transform where the time domain response is obtained by inverse Laplace transform (ILT). With regard to uniformly distributed transmission lines, this inversion can be hard and cumbersome since the function to be inverted is not rational (i.e. it is not a ratio of polynomials) but holds transcendental terms. In fact, the no-load voltage at receiving-end UR(s) is immediately given by setting IR(s)=0 so that: U R s U s Z 2 s 2 2sr sc Z c2 sr sc 1 sinh s c sc coshs 2 sZ c sr sr (1) where U(s) is the Laplace transform of the supplying generator. The switching overvoltages due to the shunt compensated cable energization are given by the ILT of (1). Unfortunately, it is not analytically possible since it has transcendental terms. Consequently, a numerical inverse Laplace transform (NILT) is necessary and has been ideated by the authors and implemented in Matlab. The proposed NILT is based on the residue theorem of the complex analysis. Differently, this paper proposes to study switching overvoltages by representing the ICL as a cascade of n cells constituted of lumped L-C ladder (with acronym LLCL) each representing a d/n length of the cable line so achieving the model of fig. 1. The number n can be chosen arbitrarily but precise results can be obtained even with n=2. At no load the receiving-end voltage is linked to the term M1,1(s) of the whole transmission matrix M (computed as a product of the transmission matrices representing the different two-port networks) and it holds only polynomials i.e. it is a rational functions whose ILT is immediate. By assuming an EHV (400kV) 2500 mm2 single-core cable system with = 0,576 mH/ km, c=240 nF/ km and d=30 km shunt compensated with sr= 5,25 H and with sc= 76,8 mH, it is possible to obtain the transient overvoltages shown in fig. 2. The EMTP-RV model has been chosen as reference and the NILT and LLCL have been compared with it. Despite its extreme simplicity, in the evaluation of the peak overvoltage LLCL method gives an overestimate of 1,07% (1,701 p.u. versus 1,683 of EMTP-RV). JICABLE15_0024.doc 29 ℓd/n ℓsc ℓsr u(t) cd/n ℓd/n R cd/n ℓsr uR [p.u.] Figure 1 EHV shunt compensated ICL represented by a cascade of lumped L-C ladder t [ms] Figure 2 Transient overvoltage comparison in an EHV shunt compensated ICL JICABLE15_0025.docx Frequency dependency of single-core cable parameters Jarle J. BREMNES (1), Gunnar EVENSET (2) 1 - Unitech Power Systems, Oslo, Norway, bremnes@unitech.no 2 - Power Cable Consulting, Halden, Norway, Gunnar.Evenset@Powercc.no It is expected that the need to obtain frequency dependent cable parameters is growing, for example in relation to future HV cable links, and that these may be needed both for AC and DC cables. There are also examples of cable links that are designed for initial operation at (HV) AC, with planned subsequent conversion to HVDC. As capacitance may be considered constant for the frequency range up to the 100th harmonic (6 k Hz at 60 Hz fundamental), the challenge then lies in predicting the series parameters (i.e., resistance and inductance) with reasonable accuracy within the frequency range: DC to 6 kHz. When identification of series parameters is concerned, mainly longitudinal metal constituents are of importance. When disregarding differences in insulation system, the single core cable design is quite similar for AC and DC, and this applies to land and submarine cables except for the armour.. Submarine cables will usually be designed with heavier mechanical reinforcement in the form of (additional) armour. The metal members of a single core cable will typically include: Conductor (copper or aluminium) Lead sheath/Al sheath/Cu wires, possibly with steel tape radial reinforcement Steel armouring in the form of a single layer or two layers of carbon steel wires (magnetic) or Cu armour wires on single core AC cables (non-magnetic) The inter-axial distance between installed cables also play an important part in identifying resistance and inductance in the lower part of the frequency band. Although the standard does not explicitly state this, the long trusted, and empirically based, formulae in IEC 60287 were developed for power frequency only. This can easily be verified through comparison with simple, analytic expressions for inductance at DC and at the upper frequency limit (6 kHz). It is also well known that metal sheath losses cause a fundamental frequency power loss that peak at a certain inter-axial distance, and are reduced both for increasing and decreasing distance. A similar effect could be expected at a fixed inter-axial distance and varying frequency. This paper describes the great detail of information that can be obtained through application of finite element analysis (FEA) to single-core cables. FEA is basically a numerical method which identifies the electromagnetic field solution based on the fundamental principle of physics: minimization of energy. When considering longitudinal currents only, two-dimensional FEA will not impose any practical limitations with respect to computational power/time required. For the sake of simplicity, this study is limited to assigning constant magnetic permeability to magnetic steel members (armour), thus excluding possibly significant non-linear effects. Even for this simplified case it is revealing to see the inherent complexity in power loss distribution between the metal members as functions of frequency. Obtaining similar behavior by means of simple formulae is considered unlikely to succeed within the frequency range considered here. JICABLE E15_0025.do ocx Fig. 1. E Example of lo oss distributio on for the me etal members s obtained fo or a typical H HVDC cable The losss distribution shown in Fig. 1 clearly illustrates th hat calculatio on of single-ccore cable re esistance and indu uctance is anything a butt straightforw ward, even when w (possibly) non-lineear propertie es of the armour a are ignored. Conclusions: T The nature of o HV powerr cables is fa ar more com mplex than th hey are norm mally given credit c for, a and they ma ay severely in nfluence ove rall power sy ystem properrties. T The finite ellement meth hod is an exxtremely use eful analysis tool that haas been far too long o overlooked in everyday electrical e pow wer engineerring. JICABLE15_0026.docx Observation of space charge accumulation in cable insulating materials at voltage polarity reversal Yasuhiro TANAKA(1), Ryota KODERA(1), Tsuyoshi KATO(1), Hiroaki MIYAKE(1) , Hiroki MORI(2), Yukihiro YAGI(2) 1 - Tokyo City University, Tokyo, Japan, ytanaka@tcu.ac.jp 2 - VISCAS Corporation, Chiba, Japan, h-mori@viscas.com Investigation of space charge accumulation process in cable insulating materials at voltage polarity reversal is carried out using PEA (pulsed electro-acoustic) measurement system. It is one of important research objects in HVDC (High Voltage DC) system because the polarity reversal is necessary to change a direction of current flow using a LCC (line commutated converter). The space charge accumulation in the cable insulating material is said that it strongly affects the breakdown characteristics. However, while some space charge accumulation measurement results have been reported as the main reason of the breakdown of the insulating materials under a severe condition like more than 100kV/mm, there is no reports that the space charge accumulation directly affects to the breakdown or severe enhancement of the electric field under a relatively low stress close to the working voltage. On the other hand, many engineers have pointed out that the polarity reversal test on a conventional XLPE (cross-linked polyethylene) cable showed somehow dangerous results including the breakdown. However, there are few attempts for the measurement of space charge accumulation at the voltage polarity reversal because it is hard to apply a high voltage to the thick XLPE sample including some crosslinking by-products. In a space charge measurement, a thin film like several hundred-micrometer-thick is preferably used to apply a high electric field to it. However, the crosslinking by-products easily volatile from such thin films and the measurement results on such sample is not reflect the actual condition of the material. That the reason why the space charge accumulation characteristics at the dangerous situation of the polarity reversal has not been investigated. Authors have showed that such existence of the crosslinking by-products is important factor for the space charge accumulation strongly affecting the breakdown strength under high DC stress. In this report, we tried to measure the space charge accumulation process in a flesh XLPE sample including the crosslinking by-products and it was found that a huge amount of so called a packet like charge, which was enough to enhance the electric field significantly, generated at the polarity reversal of a relatively low DC stress. It enhanced the electric stress locally in the sample by almost twice of the applied average stress. Therefore, it must affect to the polarity reversal test for the actual products of the cable. On the other hand, it is said that such a problem is not observed in a DC cable using a specially improved XLPE as the insulating layer. We also tried to measure the space charge accumulation characteristics in SXL-A, one of improved XLPE material using nano-composite technique, under the same polarity reversal condition which is applied to the conventional XLPE sample. As a result, we found that the packet-like charge was not observed in the sample. It means that such material is applicable to the HVDC system using the LCC. Key words HVDC cable, XLPE, Polarity reversal, Space charge, PEA method, Crosslinking by-products, Nanocomposite JICABLE E15_0027.do oc Effec ctive on n-site te esting a and non-destru uctive d diagnos sis of aged (E) HV power new installed and service s p c cables up to 230kV V Edward GULSKI (1),, Rogier JON NGEN (1), Ja arosław PAR RCIAK (2), Rafael MINAS SSIAN (3), Alexandra A RAKO OWSKA (4),, Krzysztof SIODLA S (4) 1 - onsite e hv solution ns ag, Luzern n, Switzerlan nd, e.gulski@ @onsitehv.com m, r.jongen@ @onsitehv.co om 2 - onsite e hv solution ns Central Eu urope Sp. Z o o. o. Warsaw w, Poland, j.p parciak@onssitehv.com 3 - onsite e hv solution ns Americas Inc, Toronto , Canada, r.m minassian@o onsitehv.com m 4 - Pozn nan Universityy of Technology, Poznan n, Poland, ale eksandra.rak kowska@putt.poznan.pl, @put.poznan.pl krzyssztof.siodla@ It is know wn, that an insulation i faiilure of a pow wer cable ca an occur as a result of thhe normal op perational voltage or during a transient vo oltage due to o lightning or switching surges. s Mosst failures oc ccur as a result off localized electrical are higher than e stresses that a t the die electric strenngth of the dielectric materialss in the area of the localized stresss or if the bulk b dielectric c material ddegrades to the point where it cannot withstand the ap pplied voltag ge. To find th his defect (re esult of poorr installation or heavy service cconditions) prior p to a failure, on-site tests are ap pplied to assess the quallity and cable system integrity as well as th he availability y and reliabillity of the cab ble circuit. Modern on-site testing and diag gnosis of po ower cables up to 230k kV consists of voltage withstand w testing, p partial discha arge detectio on and dissip pation factor measurements. Since laast 14 years more m and more the e use of dam mped AC (DA AC) energizin ng is getting worldwide w attention for 1. a after-laying testing t of new wly installed cable system ms, see figurre 1 as well aas 2. m maintenance e and diagno ostic testing o of cable syste ems in opera ation which arre fundamen ntal for the re eliable opera ation of unde erground pow wer distributtion and tran nsmission networkss. Having iin mind the existing IEE EE 400 and new up-coming IEEE 400.4 4 Guidee for Field-T Testing of Shielded d Power Cable Systems s Rated 5kV V and Abov ve with Dam mped Alternaating Currentt Voltage (DAC) u under ballotiing for the use of DAC C testing in n this paperr different innternational practical applications of dam mped AC voltages and ttesting proc cedures for on-site testi ng and diag gnosis of ound power cables up to 230kV w will be discu ussed based on generaal considerattions and undergro practicall examples. F Figure 1: Exa ample of a DA AC after-layiing test of a 6.4 km long 110kV XLPE E cable circuit. JICABLE E15_0028.do ocx Expanding the Perfformanc ce Poten ntial of the Uniiversal Cable C Syste em by the use e of Do ow END DURANC CE™HF FDC-420 02 EC Water Tree Retardan R nt Cross slinked Polyethylene In nsulatio on. Stephen n CREE (1), Christian C ANDERSSON ((2), Paul BR RIGANDI (3), Håkan BRIN NGSELL (4) 1 : Dow Electrical & Telecommun T nications, Ba achtobelstras sse 3, Horgen, Switzerlannd, CH 8810. cree@ @dow.com 2 : nkt ca ables AB, Ka allviksvagen 18, Falun, S Sweden, SE-7 791 29. christtian.andersso on@nktcable es.com 3 : Dow Electrical & Telecommun T nications, 40 0 Arcola Rd.., Collegeville e, Pennsylvaania, PA 19426, USA. gandi@dow.ccom pjbrig 4 : nkt ca ables AB, Ka allviksvagen 18, Falun, S Sweden, SE-7 791 29. hakan n.bringsell@ @nktcables.co om Tradition nally, electriccal power dis stribution is d divided betw ween undergrround cabless and overhe ead lines, where underground cables dominate in urba n areas and overhead lin nes more coommon in rurral areas. The design of the un nderground power p cable o or overhead line is very different. d How wever the us se of nkt’s Universa al Cable Sysstem is begin nning to blurr this differen nce as the Universal U cabble system has h been shown to o work equa ally well whetther installed d overhead on o poles, or buried undeerground or even e in a submarin ne environm ment. Clearlly the adva antage of using u the same type oof cable in multiple environm ments, lowerrs investmen nt and mainttenance cos sts while delivering a neew and cost effective method ffor 12-36kV power distrib bution. Identified d problems for f grid owne ers with ove erhead lines are e.g. falling trees, snnow loaded trees t and ice loadss. Falling trees due to storms may ca ause perman nent failure that t must bee addressed with high priority. Besides gre eat expense, these incid dents cause e poor and hazardous h w working enviironment. Snow loads can make trees and d branches ccome into co ontact with wires. w These occasions generates g heavy and time conssuming work kload, with lo ong downtim me as a resu ult. Heavy icee and snow loads on electrica al wires cause outage due to broken wires and jo oints. The Un niversal cablee system is designed to withsttand these na atural pheno omenons. Exxperience sho ows excellen nt performancce compared d to other existing solutions. duced Unive ersal cable co ores using Dow D ENDURA RANCE™ HF FDC-4202 Recentlyy nkt cables AB has prod EC (C-4 4202), the new n enhance ed performa ance water tree t retardan nt crosslinkeed polyethyle ene (TRXLPE) in nsulation fro om Dow Elec ctrical & Tele ecommunica ations. The Universal U caable cores ha ave been subjecte ed to the Cen nelec 500 Hz z wet ageing g protocol att SINTEF, Norway. As sshown in Figure 1 the 500 Hz ttest results demonstrate d d excellent rretained breakdown perfformance of the cable cores with breakdow wn values well w in excess s of Cenelec requirementts (6 cables > 18kV/mm or 6 > 14kV V/mm, 4 > 18kV/mm m and 2 > 22 2kV/mm). Figure 1 1: Retained breakdown voltage of n nkt cable co ores based upon u Dow E ENDURANCE HFDC4202 EC C following Cenelec C 500 0 Hz accelerrated wet ag ging test. JICABLE E15_0028.do ocx Cable lifetime data generated by Dow E lectrical & Telecommun nications coonfirms the excellent performa ance of mediium voltage (MV) ( cables made with C-4202. C Figure 2 shows ttime to failure e data for full size 15kV MV ca able subjectted to the Acccelerated Cable C Life Te est (ACLT) pprotocol. As Figure 2 illustrate es, cables made m with C--4202 show significantly y increased time t to failuure and charracteristic lifetime a as compared d to current commercial TR-XLPE in nsulation sys stems. The ccharacteristic c time-tofailure fo or MV cable with C-4202 2 is more tha an five times s the existing g commerciaal grade (HF FDB-4202 EC); app proximately 2,500 2 days versus v 350 d days. To date the new en nhanced TR R-XLPE insulation has experien nced only one e failure at more m than 1,0 000 days. Figure 2 2: 4,4 ACLT of 15kV medium voltag ge cable made with C-42 202 (4.4mm insulation). An addittional benefitt of using thiis high perfo ormance tree e retardant in nsulation is tthat both bon nded and strippablle insulation shields can n be employyed with C-4202, offering g cable mannufacturers a broader design cchoice with a TR-XLPE system. In fact, easy strip s semi-co onductive inssulation shie elds work exceptio onally well wiith C-4202 in nsulated cab bles and nkt cables AB is s able to em ploy this com mbination in Universal system cable c cores. This pap per highlightss the most re ecent develo opments in th he design of Universal caable systems s from nkt cables A AB, Sweden.. Furthermorre, the high retained bre eakdown stre ength in the Cenelec 500 Hz test and the increased characteristic time to failu ure in the AC CLT protocol, raises the possibility that cable cores ma ade with C-4 4202 insulation can be co onsidered in the design of o higher volltage power cables or in reduce ed wall thickness insulatiion MV cable e designs. Key word ds: Universa al cable, XLP PE insulation,, medium voltage cable, water w tree reetardant JICABLE E15_0029.do oc Long lengths s transm mission power cables on-site testing up to 500kV V by dam mped AC A voltag ges Paul P. S SEITZ (1), Ben QUAK (1), Edward G GULSKI (2), Manuel M WILD D (3), Frank DE VRIES (4 4) 1 - Seitz Instrumentss AG, Niederrohrdorf, Sw witzerland, bq q@seitz-instrruments.ch, ppps@seitzinstru uments.ch 2 - onsite e hv solution ns ag, Luzern n, Switzerlan nd, e.gulski@ @onsitehv.com m 3 - Stuttg gart Technical University y, Stuttgart, G Germany, ma anuel.wild@ieh.uni-stuttggart.de 4 - Liand don B.V, Alkm maar, The Netherlands, ffrank.de.vries@alliander..com Since 20 004 damped d AC (DAC) Hz voltagess are in use for on-site testing and diagnosis of o (E) HV cables. DAC testing g is an altern native metho od to conven ntional ACRTS testing aand has got at many utilities a and service providers p its acceptance ffor: q quality contro ol of cable and accessor ies installatio on during afte er-laying testting, m maintenance e testing during operation n or in conjun nction with re epair work affter a failure, ccondition asssessment of service aged d cable circu uits, In additio on to the equ uivalence of sinusoidal d amped AC voltages v (in the t frequency cy range of 20-300Hz) compare ed to the 50((60) Hz netw work stressess the charac cteristics of the applied ttechnology meets m the specifica ation of an on n-site testing g system: L Lightweight modular m systtem, C Compactnesss in relation to the outpu ut voltage, L Low effort fo or system ass sembling, L Low power demand, d even for long ca able lengths, L Low level noises and d possibilityy of sensittive PD de etection andd dissipatio on factor m measuremen nts. In this co ontribution th he newest mo obile solution ns for DAC field f testing up u to 500kV oof cable leng gths up to 25 - 40 km will be presented. p As A an innova ation to the existing e single side (E) H HV DAC sys stems for energizin ng long lengtths and for PD P detection on longer ca able lengths compact higgh power sou urces with an additiional range extension e solution will be e presented, see Figure 1. Finally, b based on the e field experiiences as co ollected in the e past 10 years and to s upport different types of on-site tests e.g g. for after--laying, mai ntenance and diagnosttics purposees, the sele ection of procedures will be diiscussed. AC test syste em with doub ble side PD testing t and ddiagnosis exttender for Figure 1: Example off a 300kV DA nsmission ca able circuits long tran JICABLE15_0030.doc New integrated solution for DAC and VLF testing and diagnosis of distribution power cable circuits Ben QUAK (1), Paul P. SEITZ (1), Edward GULSKI (2), Frank DE VRIES (3) 1 - Seitz Instruments AG, Niederrohrdorf, Switzerland, bq@seitz-instruments.ch, pps@seitzinstruments.ch 2 - onsite hv solutions ag, Luzern, Switzerland, e.gulski@onsitehv.com 3 - Liandon B.V, Alkmaar, The Netherlands, frank.de.vries@alliander.com Referring to the worldwide practice in testing and diagnosis of distribution power networks both damped AC (DAC) and very low frequency (VLF) test voltages have been accepted and widely in use for after-laying, maintenance and diagnostic testing of medium voltage cable circuits. In the last 10 years it has been demonstrated that 1. PD monitored voltage withstand testing using DAC voltage is a very effective method to detect most insulation weak-spots. In combination with dissipation factor estimation (tan δ) it can be used to investigate the degradation of oil-impregnated insulation, 2. The voltage-withstand testing using sinusoidal VLF is sensitive to demonstrate the insulation weak-spots. In combination with dissipation factor measurement (tan δ) it is an excellent diagnostic tool for moisture related defects and cables with water-treeing. As a result the recent IEEE 400 Guide (2012) and several national standards and guidelines describe that both technologies represent effective test voltages for testing and diagnosis of MV cable networks. As the conventional DAC and VLF technologies used till now are respectively DAC or VLF single system solutions it is obvious that a multi voltage source solution would be an optimal solution for an effective on-site testing and diagnosis. Moreover in add-on to DAC or VLF voltage withstand testing the application of PD detection at DAC and dissipation factor estimation at both DAC and VLF are possible to localise discharging defects and/or to asses the insulation degradation of all types e.g. XLPE, paper-oil, EPR of cable insulation. In this contribution supported by practical application an innovative (paten pending) new generation of combined DAC and VLF sinus voltage test and diagnosis (PD and tan δ) solution up to 40kV will be presented. Figure 1: Example of a DAC and VLF testing of 36kV XLPE cable circuits. JICABLE15_0031.docx Experiences of combined HV & EHV qualifications to IEC, AEIC and challenges IEEE 48 & 404 Caryn M. RILEY, Josh PERKEL, Raymond C. HILL, and R. Nigel HAMPTON 1 - NEETRAC, Atlanta, USA, caryn.riley@neetrac.gatech.edu ray.hill@neetrac.gatech.edu, nigel.hampton@neetrac.gatech.edu The use of XLPE cable systems continues to increase in the Americas due to economies that achieved and excellent reliability for modern installations. As the use increases and becomes more widespread in the utility space the importance of qualification procedures and their applicable range of approvals becomes increases. Currently US utilities are very comfortable with the cable system approaches of the latest iterations of the AEIC & IEC standards. However the benefits of IEEE standards (48 & 404) are still used in some applications. As described in the last Jicable Conference the combined AEIC / IEC test approach (intercalation of the most searching elements of two separate standards) is very common and well accepted by users. The combined AEIC / IEC approach has led to the speculation that it may be possible to make further combinations, for example IEEE48 with IEEE404 or IEEE48 & 404 with AEIC / IEC etc. The attraction is the allure of reduced time and cost, on a per component basis, when compared with the separate approach. Since Jicable 11 both the IEEE 48 and 404 standards have been significantly updated; such that even if a combination may previously have been attractive, the current embodiments make it much more difficult. Thus this paper focuses on the issues associated with bringing one or more of the IEEE standards into the combination approach. Each IEEE standard includes quite different test orders, philosophies on Pre & Post tests as well as requirements for test temperatures. Although, on paper, it is feasible to add an IEEE test to the well established IEC / AEIC combination (described as a “Super Combo Test”) the technical elements are very stretching for a laboratory / cable system. Consequently this presents a very interesting Risk / Benefit optimisation for those using this route. The optimization includes effects, which increase the risk such as: number of cycles, likelihood of missed cycles due to the complexity of the requirements, increased number of accessories, elevated voltages etc. The paper will focus on three areas: 1. Review the current (2010 to 2014) test experience, similar to that previously reported by Pultrum et al in CIRED09, with the combined (AEIC / IEC) and separate (IEEE) tests {to the recently revised standards}. The authors find higher success rates in tests than noted in previous reports (Pultrum et al). 2. Consider the impact of the differing test factors in the standards (eg 2 hr vs 6 hr hold requirements AEIC vs IEEE), on test laboratories and cable system. There will be particular focus on the impact of the temperature transients on accessories imposed by the required currents. 3. Use of available test experience (Figure 1) to quantitatively estimate the increased risks associated with added combinations of tests and components (ie typical 2 joints in IEC vs 4 required by IEEE), thereby more clearly understanding the value optimisation. JICABLE15_0031.docx 220 200 R ELAT IV E R IS K 180 NUMBER OF ANNEXs INCLUDED 0 1 2 160 140 120 100 100 80 60 3 4 5 6 NUMBER OF COMPONENTS (Cable, Joint, Termination) IN TEST Figure 1: Anticipated Risk (current 2010 - 14) in combined AEIC / IEC tests (Cable, Joint, 2 Terminations as as complexity of tests increase with added components and tests (Annex’s E & G in this case but could include IEEE) reference = 100) JICABLE15_0032.docx Non-contact surface metrology screens in XLPE cables of degraded conductor Jorunn HOELTO, Kristine BAKKEN, Sverre HVIDSTEN (1) 1 - SINTEF Energy Research, Sem Saelands vei 11, Trondheim, Norway jorunn.holto@sintef.no Polymer insulated cables today have an axial water tight design which prevents liquid water from entering the area between the conductor strands. This area is usually filled with swelling powder or strand sealing materials. Thus, liquid water penetrating the area between the strands is less likely, but may happen after a service failure. Liquid water causes corrosion of the Al strands and further initiates environmental stress cracking (ESC) of the conductor screen at the interface. This forms porous structures, so-called Stress Induced Environmental Degradation (SIED), finally bridging the conductor screen radially. Such conditions strongly accelerate vented water tree growth from the conductor screen. The main purpose of this paper is to present results from non-contact surface metrology characterization of SIED structures in a 12kV cable with stranded conductors filled with artificial salt water for 1 month at 40°C. These measurements were compared to optical microscope examinations at the same surface locations. The bulk morphology was examined using a Scanning Electron Microscope (SEM). The results showed that after immersing the sample in hot tap water for three hours, the SIED structures were found to be a permanent swelling of the material clearly revealed by the highresolution 3D imaging. The structure did not change shape or appearance after 2 hours in ambient conditions after wetting. Additional characterization using a Scanning Electron Microscope (SEM) revealed porous structures in the conductive screen with fibrils stretching across the gaps. Key words: XLPE, aluminium conductor, corrosion, SIED, ESC JICABLE15_0033.doc Installation and commissioning of Patuxent River Crossing (HDD, 1.4 km) Project in US Jaeyun JOO (1), Seungik JEON (1), Byungsoo KIM (1) 1 - LS Cable & System, Gumi, Republic of Korea, jaeyunjoo@lscns.com, sijeon@lscns.com, bskim@lscns.com Southern Maryland Electric Cooperative (SMECO) planed and designed the Holland Cliff to Hewitt Road 230kV transmission line project which is part of SMECO’s overall Southern Maryland Reliability Project (SMRP). The SMRP includes a segment of underground transmission line crossing the Patuxent River using 230kV high voltage solid dielectric (XLPE) cables. The initial installation was planned for a single circuit 230kV XLPE cable system with provisions for a second circuit to be installed in the future. The land based portion of the route will be installed in concrete encased duct bank with conduit provisions for a future circuit. The Patuxent River crossing portion of the route was installed in a Horizontal Directional Drill (HDD) with a separate parallel HDD with conduit installed for a future second circuit The Patuxent River Crossing consists of two separate parallel 1.4 km HDDs and 3~4 f-PVC conduits for each HDD. This length of HDD is one of the longest HDD cable pulling method in US. As a result there was some technical issues (such as conduit installation, cable pulling, etc.) should be solved prior to the installation. As a prime contractor, LS Cable & System supplied and installed 230kV XLPE 1600SQ copper conductor cable and accessories with various technique and method to install into the 1.4 km HDD. As a result it was successfully commissioned in Oct. 2014 and commercially operated in Nov. 2014. This paper covers the philosophy and the techniques to install the cable through the long length (1.4 km) HDD as below. - Manufacturing and transportation long length cable drum (1.4 km) - Conduit installation and jointing process including debeading at joint area - Cable pulling process including friction coefficient testing - Sheath bonding method (hybrid, cross bonding) and related current rating - Commissioning test JICABLE15_0034.doc Development and engineering application of 160kV XLPE to three-terminal VSC HVDC project in China Shuai HOU (1), Mingli FU (1), Linjie ZHAO (1) 1 - Electric Power Research Institute of China Southern Power Grid, Guangzhou, China, houshuai@csg.cn, fuml@csg.cn, zhaolj@csg.cn The world’s first ever multi-terminal voltage source converter (VSC) high voltage direct current system was put into operation at the end of 2013 for the connection of Nan’ao island wind farm to the onshore grid in China. The project, rated at 160kV and 200MW, has deployed a 28.3 km-transmission system which comprises XLPE insulated HVDC land and submarine cables and overhead lines by considering the geographic condition of transmission right-of-way. XLPE insulated DC cable and its accessories was also the first ever developed at such voltage level in China by then. The configuration of the project is illustrated in Figure1. Figure 1 Configuration of Nan’ao VSC project This paper presents the technical issues of 160kV XLPE insulated HVDC cable development and its engineering application in this three-terminal VSC project. For the material development and cable insulation design, a good effort has been made on conductivity characteristic of insulation material with temperature and electric field, insulation material breakdown tests, and space charge behavior. Submarine cable is made of swelling tape for water blocking, and an 18-core fiber-optic is buried between lead sheath and armor steel wires for monitoring and communication. The prefabricated joint and termination were developed by optimizing interface material properties to decrease the space charge accumulation. The cable system was tested by referring to CIGRE TB 496 “Recommendations for Testing DC Extruded Cable Systems for Power Transmission at a Rated Voltage up to 500kV”. Due to the connection of cable system and overhead line, the maximum potential lighting and switching impulse voltage were calculated by PSCAD/EMTDC simulation to determine the insulation coordination parameters. Superimposed impulse voltage tests have been successfully conducted on this basis. Apart from the development test, routine test and sample test suggested by CIGRE TB 496, a new testing procedure of AC-DC-AC withstand tests with partial discharge measurement in AC test was agreed between manufacturer and user to check the insulation integrity after manufacture and DC voltage test respectively, which has been proved to be an effective testing method to ensure the quality of XLPE insulated HVDC cables. The cable system has been put into operation for almost a year and its conditions and system characteristics are presented and analyzed as well based on the data obtained from Nan’ao on-line monitoring system. JICABLE15_0035.docx The Experience in Applying New Recovery Voltage Parameters for the Impregnated Paper Insulation Cable Condition Diagnostics. Alexander KONONENKO (1), Alexey HOHRYAKOV (1) 1 - FSUE “RISI", Turaevo 8, Lytkarino, Moscow region, Russian Federation 140080 aikononenko@niipribor.ru, avhohryakov@niipribor.ru The form and volume of recovery voltage (RV) in dielectrics is defined by two simultaneous processes - space charge depolarization and volume conductivity. There were some new RV parameters examined, which allow controlling two relatively independent processes of electric insulation aging: the volume conductivity change and volume charge state change. For the volume charge state control a PIRV polarization indicator on recovery voltage is introduced, for the volume conductivity control a LIRV electric conductivity indicator is introduced. Both these condition indicators are calculated from is approximated by the exponent amount with RV max value. For this purpose the RV curve parameters and ∑ ∙ exp , (1) takes on both positive and negative values. It is customary to where is time. In the model (1) assume that RV is of negative polarity, so here the short-lived components are of positive polarity. PIRV is defined as a ratio of the RV maximum positive components : 10 ∙ , (2) and the LIRV indicator is defined as a ratio of 100 to the amount of intensities of the short-lived . to the total area of the short-lived component : (3) In both cases the multiplying factor and the modulus sign is introduced for the convenience of applying by in practice presents normalization of PIRV and LIRV condition indicators. The division of by the volume residual insulation polarization value in the moment of the beginning of RV measurement. Such normalization allows comparing PIRV for industrial insulators of various geometrical sizes and configurations, for example, for insulating cables of various lengths and crosssections. The division of by value represents a normalization of by charge value resulting from depolarization currents of the short-lived charge states. Such “internal” normalization allows quantitively evaluating the volume insulation conductivity by the LIRV value regardless of its geometrical sizes and configurations. The PIRV and LIRV values were used to evaluate technical condition of power cables with impregnated paper insulation (PILC) after a continuous exploitation in the nuclear plant unit rooms. The experimental findings allowed elaborating the criteria for evaluation of PILC cable condition in case of typical defects in this environment. The joint use of the PIRV and LIRV condition indicators and the parameters of partial discharges registered at oscillating damping voltage allowed both diagnosing the aging degree of PILC cable caused by typical defects, and determining the defect location on cable routings. Key words Electric insulation, recovery voltage, condition indicators, volume conductivity, volume charge, polarization, cable, impregnated paper insulation. JICABLE15_0036.doc Developpement of a XLPE insulating with low peroxide byproducts Mohamed MAMMERI (1), Isabelle DENIZET (1), Jean-Christophe GARD (1) 1 - General Cable, Montereau, France, mmammeri@generalcablre-fr.com ,idenizet@generalcable-fr.com, jcgard@generalcable-fr.com, The chemically crosslinked polyethylene (XLPE) is widely used in MV/HV insulating due to its good electrical properties and good thermomechanical behavior. However as a result of the chemical crosslinking, the generation of gas and polar by-products from the peroxide are generated. For safety reason related to its flammability, such gas has to be removed prior any cable termination preparation and jointing process. Furthermore, under working conditions some gas could be released along the cable and affect the reliability of the accessories. The presence of such gas modify the interface pressure between the cable and the splice body which leads to partial discharge generation and then to the dielectric breakdown. The degassing of insulating is a key parameter for the quality of cable. This step needs several days of heating according to the thickness of the insulating before jacketing. Furthermore, the polar by-products (acetophenone, cumyl alcohol…) influence electrical properties such as dissipation factor and space charge accumulations. The purpose of this article is to present a new XLPE with very low content of by-products (gas and polar) and wich fulfill the standard requirement of crosslinking density (Hot Set Test < 175%). We discuss the influence of the chemical nature of peroxide and crosslinking promoter and we display some mechanical and electrical properties. JICABLE15_0037.docx Assessing smoke and heat release during combustion of electric cables using cone calorimeter Burjupati NAGESHWAR RAO (1), R ARUNJOTHI (1) 1 - Central Power Research Institute, Bangalore, India, nagesh@cpri.in, arunjothi@cpri.in Cables are designed for transportation of electric power for long distances. In the construction of Cables different materials like PVC, FRPVC, XLPE, ZHFR etc are used as insulating and sheathing / jacketing materials. However, the polymeric materials used in cable construction may pose a great threat and can act as a medium of fuel with liberation of heat, smoke and toxic gases in the event of fire. Though Electric cables rarely cause fire, they act as pathway in the event of fire, along which fire can travel and spread. The fire behavior of cable depends on a number of factors, including their construction and constituent materials. In recent years, increasing attention has been given to fire risks relative to electrical cables, with the examination of their behavior under fire conditions not only in terms of their participation in the fire and its propagation, but also in terms of the danger of fumes emitted during combustion. Apart from smoke and toxic gases, the heat release is an important parameter which characterizes the total available energy in the material in a possible fire situation. Thus the measurement of heat release rate of burning cables is believed to be an important for quantifying the growth and spread of fire. Cone Calorimeter has become one of the most widely used apparatus for heat release measurement on cables and materials. This paper presents and discusses the data obtained on smoke and heat release measurements obtained on cables and cable materials using cone calorimeter. Power cables, communication cables, data cables and wires used for various applications in Power plant, Refineries, automobiles and other applications have been evaluated for heat release measurement. The behavior of cables have been studied at various thermal irradiances. Power cable Individual components have been evaluated at different heat fluxes in horizontal and vertical orientation. Parameters like time to ignition, mass loss rate, total heat release, heat of combustion, specific extinction area of smoke, rate of production of yields CO/CO2 ratios are also measured and discussed. Char analysis has been carried using Fourier Infra Red Spectrometer. The key parameters were obtained using cone calorimeter which enabled to ascertain the fire behavior of material under different thermal fluxes. From this study burning cables can propagate flames from one area to another or they can add to the amount of fuel available for combustion and can liberate smoke and containing toxic and corrosive gases. Key words Fire Hazards. cone calorimeter, Toxicity. Heat Release, Smoke, flammability JICABLE15_0038.docx Lethal combustion product evaluation of polymeric materials used in Power cables Burjupati NAGESHWAR RAO (1), R ARUNJOTHI (1) 1 - Central Power Research Institute, Bangalore, India, nagesh@cpri.in, arunjothi@cpri.in The generation of lethal combustion products is of primary importance in the assessment of “fire hazard” resulting from cable materials during fire accidents. The fire safety requirements in the international standards are based on exigencies of the fire behaviour of individual materials that are used in the cable system. PVC compounds have been used for decades as insulation / sheathing material in cable manufacturing due to its excellent mechanical and chemical properties. However, halogen acids, which are generally produced during combustion, are highly suffocating and can cause problems of corrosion to electrical apparatus and metallic structures even months after the fire. Statistics indicate most of the fire victims die or affected by smoke rather than the Asphyxia which is the principal mechanism of intoxication, mediated by oxygen depletion, carbon monoxide inhalation and sometimes even by hydrocyanic acid inhalation. In recent times due to increase in fire accidents and with loss of lives and property, regulatory authority have enforced strict laws and regulations to minimize the risk of fire by assessing ‘Fire hazard’ of materials used in any industry. Therefore interest has centered on in the development of polymers which evolve reduction in smoke levels and toxic gases. PVC materials are replaced with low smoke zero halogen (LSOH) materials which are free of Chlorine, Fluorine, Bromine and Iodine. The fire safety is addressed through small scale flammability, smoke /toxicity of fire gases, determination of halogen acid generated and performance criteria is based on guidelines laid in the international standards. A study was undertaken in the laboratory of Central Power Research Institute, Bangalore, India to assess the toxicity products of cable materials. This paper presents and discusses the toxicity of the products of combustion in terms of small molecular species arising when a small sample of a material is completely burnt in excess air under specified conditions. The evaluation of the toxicity of fire gases is made through the determination of the following gases: Carbon oxides(CO, CO2), halogen acids (HCl, HBr, HF), Prussic acid (HCN), nitric oxides (NOx), acrylonitrile (CH2CHCN), Phenol, H2S as per NES 713/NCD 1409 standards. Halogen acid determination have been carried out in accordance with IEC 754 part 1 & 2 standard methods. Further Char analysis has been done using Fourier Transform Infrared spectrometer and Scanning Electron microscopic techniques. Cable insulation, filler and sheathing materials have been evaluated and the results are presented and discussed. Key words Toxicity, Char analysis, Corrosion, halogen acid generation, JICABLE15_0039.docx Copper or aluminium cable conductors, broadly compared in a life-cycle perspective Wim BOONE (1), Arnav KACKER (2), Remco BAL (3) 1: DNV GL, Arnhem, The Netherlands, Wim.Boone@dnvgl.com 2: PE-International, Stuttgart, Germany, A.Kacker@pe-international.com 3: DNV GL, Arnhem, The Netherlands, Remco.bal@dnvgl.com A cable conductor usually consists of copper or aluminum. Next to cost differences, each material has pros and cons that affect their use in various applications. Originally copper was the only conductor material used, later aluminium was introduced as a conductor material as well. Some utilities are in favour of copper, some utilities are using aluminium. A questionnaire was prepared that was sent to about 100 distribution utilities in 25 countries, to obtain information about the motivation behind the decision to use copper or to use aluminium conductor. After giving summarized information on the typical properties of copper and aluminium conductors and information on failure mechanisms related to conductor material, the results of the questionnaire will be presented. After this introduction to the technical aspects of copper versus aluminium and the related perception of utilities, attention will be paid to the environmental performance of both conductor materials in a Life Cycle Analysis (LCA). An investigation into the end-of-life of cables has been performed following an LCA approach for copper and aluminium power cables in Europe. This also included a thorough market survey of the cable recycling industry to reflect a real-world quantification of the end-of-life stage. The LCA aggregates the environmental impacts associated with the manufacturing, recycling effort, and credits through replacement of primary metal by recycled metal on the market. Our analysis finds that copper cables have lower net environmental impacts than aluminium counterparts for several impact categories. The relative difference in net impacts between the copper and aluminium variants becomes more pronounced for higher voltage cables. The difference amongst This paper about copper and aluminium will be completed by a proper Life Cycle Cost Analysis (LCCA), in order to compare costs over the entire lifetime. With this method, it is possible to calculate the real economic choice between cables of copper and aluminum. To find the life cycle cost, all costs over the lifetime of a cable are considered, including initial capital costs, O&M costs, cost of electric losses and residual value after demolition. These costs are discounted and totaled to a present day value. This has shown that the difference between copper and aluminium cables over their entire lifetime is not as significant as generally thought. The cost for raw copper material is about 3.5-4 times higher than aluminium but looking at lifetime costs, and within the uncertainties of LCCA over the long cable lifetime, both solutions can be considered equivalent. JICABLE15_0040.docx Dielectric diagnosis of extruded cable insulation by very low frequency and Spectroscopy techniques - A few case studies Burjupati NAGESHWAR RAO (1), K. MALLIKARJUNAPPA (2) 1 - Central Power Research Institute, Bangalore, India, nagesh@cpri.in, mallik@cpri.in Electric Power Systems comprises a large number of power cables which are quite expensive. Wide variety of cables like PILC, EPR, PVC, XLPE are in use. Many of these cables which are in service are approaching their life span. These cables and their accessories, which are subjected to various kinds of stresses during their service life undergo degradation and deterioration of insulation and hence lead to forced outages. Forced outages are of serious concern and are not economical. In order to check the quality and healthiness of a cable system, it is important to perform diagnostic tests on laid cables before setting into operation and after definite period of operation. Though there are various diagnostic test methods available, there are certain merits and demerits in each technique and no each technique can give the complete information about the healthiness of the cable. Applying effective technologies and remedial measures can reduce costs and improve the performance of cable systems. Therefore lot of research efforts and activities are directed towards a better understanding of degradation phenomena and the finding tools for insulation diagnosis and remaining life estimation techniques. Central Power Research Institute (CPRI) a premier institute in the field of power sector is rendering its services to various Electricity boards, Power Utilities, manufacturers and others in condition assessment of cables for the last few decades. Condition monitoring techniques like measurement of Insulation resistance, PI, Dissipation factor, Loss angle and capacitance, VLF testing methods are adopted to assess the condition of the cable insulation. In this paper some of the low frequency techniques are reviewed and some case are presented and discussed. Case studies include the assessment of ddistribution cables which were submerged under water for more than 45 days were assessed using VLF technique in addition to other techniques like insulation resistance and dc voltage withstand test. Technique used for extraction of water from the cable termination is discussed. The consequences of bad crimping of cable lugs and improper cable terminations on the penetration of water into the cable length are highlighted. The study showed abnormal dielectric losses in the cable insulation as a result of highly polar contaminants in the cable. The application of low frequency tan delta technique and its usefulness in assessing the failed cable are enumerated. Low frequency partial discharge measurements conducted on 33kV to identify localised incipient defects are presented and discussed. Few case studies using dielectric spectroscopy are presented and discussed. Key words Dielectric diagnosis; very low frequency tan delta; Very low frequency partial discharge, Waterlogged cables, VLF tests JICABLE15_0041.docx Effect of the Fault Impedance on the Performance of Directional Over Current Relays in Medium Voltage Power Cables- A Case Study Ahmed Mohamed Amin HUSSEIN DAR Engineering, Cairo, Egypt, ahmed.amin@dar-engineering.com The most common type of cable faults is the contact asymmetrical faults. The contact fault is described as a partial or total short circuit between cable cores or between cores and cable sheath. The value of fault impedance varies from zero Ohms to many mega Ohms. These faults are caused by the internal discharge in the cables that results from gradual deterioration of the insulation materials between cores and sheath. Asymmetrical faults are single phase to ground, line to line and double line to ground through impedance faults. One of the most effective techniques for protection of medium voltage cables is the Directional Over Current relays (DOC). However, the fault impedance may lead to mal-operation of these relays if it is improperly set. In this paper, different medium voltage network’s configurations in Saudi Arabia are analyzed. All faults types are simulated using ETAP software which is an efficient user friendly tool in power system analysis studies. The directional over current relay settings are calculated for each network configuration and the effect of the value and nature of fault impedance (resistive or inductive) is illustrated. After that ETAP software is used for validation of these results on a real case study in Saudi Arabia. The directional over current relay settings of 13.8kV incomer feeders with the possibility of parallel operation of two 115/13.8kV transformers are calculated for Royal Commissioning JUBAIL substation. JICABLE15_0042.docx Comparison of losses in an armoured and unarmoured three phase cable Thomas EBDRUP (2), Filipe FARIA DA SILVA (1), Claus L. BAK (1), Christian F. JENSENSEN (2) 1 - Aalborg University, Aalborg, Denmark, ffs@et.aau.dk , clb@et.aau.dk 2 - Energinet.dk, Erritsø, Denmark, teb@et.aau.dk , cfj@energinet.dk As an increasing number of wind farms are placed offshore, the energy harvested from the wind turbines must be brought to shore. This is done by using submarine cables from the offshore collector platform, which is collecting all the power from the wind turbines, to a suitable onshore substation. For practical and economic reasons it is preferred to use three core submarine power cables. Three core submarine cables are armoured in order to provide mechanical protection of the cable and to achieve the tensile strength needed when the cable is installed. The existing IEC 60287-1-1 standard is used to determine the current rating of armoured three-phase submarine cables. The formulas in the standard are based on work done back in the 1920’s and 1930’s, and in the cable industry, the method used in IEC 60287-1-1 is known to overestimate the losses of three phase armoured cables. Overestimation of the cable losses can result in core cross-sections too large and thereby a more costly cable installation. Therefore, further research is needed in order to develop new analytical equations capable of a more accurate estimation of the losses in three-phase armoured cables. This paper presents several measurements performed on both an armoured and unarmoured submarine cable of the same type and length. The AC resistance of both cables is presented and compared. For the armoured cable the AC resistance, as a function of the power conductor current, is presented. The induced currents in the lead screens of both the armoured and unarmoured cable is presented and compared. The circulating currents in the armour are investigated for different connections (e.g. armour short circuited, armour open in both ends) in both balanced and unbalanced operation. It is also investigated if the different armor connections have any influence on the AC resistance. Furthermore the influence of the semiconducting layers covering the lead screens is addressed. The measurements presented in this paper will help understand the effect of the armour and thereby contribute to the understanding of losses in armoured submarine cables. The measurements will also help identifying the areas that need more attention in order to develop accurate, easy to use, analytical formulas for estimating the ampacity of three phase armoured submarine cables. This paper is one in a series of papers that will focus on developing more accurate formulas for calculating the ampacity of three phase armoured submarine cables. The papers will be based on reaches done in the project “Modelling of long armoured three phase submarine power cables” the project is a collaboration between Aalborg university, the Danish TSO Energinet.dk and Dong Energy. JICABLE15_0043.docx Development of 320kV subsea/underground HVDC extruded cable system Naoto SHIGEMORI (1), Yasuhiro SAKAI (2), Hiroki Mori (1), Yukihiro Yagi (1) 1 :VISCAS corporation, Ichihara, Japan n-shigemori@viscas.com, h-mori@viscas.com , yu-yagi@viscas.com, 2 :VISCAS corporation, Hiratsuka, Japan y-sakai@viscas.com In recent years, high voltage direct current (HVDC) technologies have been focused in fields of grid interconnection, large capacity and long distance transmission, for example to islands and from offshore wind farms. HVDC transmissions can make their total costs lower than HVAC in longer distance use. A lot of applications of HVDC system have been reported all over the world, for example in use of long distance submarine transmission. However, oil filled or mass impregnated paper insulated cables have ever been conventionally used in such applications. Nowadays, extruded cables are preferred due to their advantage in load capacity, impact to environment and maintenance. VISCAS has developed the original insulation material including the special conductive inorganic filler to XLPE. The material was named as “SXL-A”. “SXL-A” has good electrical performances in not only space charge and volume resistivity but also breakdown strength. VISCAS has also developed premolded accessories made of ethylene-propylene rubber (EPR) as insulation material for HVDC system and has confirmed their excellent performance for DC electric field. As for land cable system development, DC320kV prequalification test in accordance with CIGRE TB496(VSC-compliant) was carried out. Tested cable had large size conductor (2500 mm2), “SXL-A” insulation layer. The test circuit, in length 190 m, consisted of 4 pre-molded joints, 2 outdoor terminations and 2 GIS terminations. In order to simulate an actual installation condition on site, pipe section, direct buried simulated section and tunnel simulated section were included in the circuit. Every load cycle tests and all of withstand tests after load cycle were successfully completed without any problem. In addition, DC320kV type test in accordance with CIGRE TB-496 (VSC-compliant) also was conducted. The test circuit, in length 60m, consisted of 2 pre-molded joints, 2 outdoor terminations. Every test sequences were successfully completed without any problem. For sub-marine cable system, technologies of factory joint, land joint and repair joint and outer armoured cable are needed. In order to evaluate the performance of them, another 320kV type test was demonstrated. It was in accordance with CIGRE TB-496 (LCC compliant) and ELECTRA 189. The test circuit consisted of 1 factory joint, 1 land joint, 1 pre-molded joint as repair one, 2 outdoor terminations, 2 GIS terminations and cables. Cables including factory joints were applied to coiling test and tensile bending test before the construction of load cycle test loop. Every load cycle tests and all of withstand tests after load cycle regulated in CIGRE TB-496 were successfully completed without any problem. On the other hand, prequalification test using another test loop similar to the type test’s As an achievement of those development activities, VISCAS was awarded his first HVDC XLPE cable project in Sweden. Supply and installation of DC+/-300kV cable and the accessories are implemented in 2013-2014. Cable system with DC+/-300kV is higher level of rated voltage in the field of HVDC XLPE application. JICABLE15_0044.doc Improving performance of medium voltage cables heat shrink accessories Abdullah A ALDHUWAIAN Saudi Electricity Company, Buraydah, Qassim Area aadhwaian@se.com.sa As the network of National Grid SA is enormously expanding, medium voltage power cables are extensively used. Knowing that medium voltage power cables are responsible for considerable amount of network interruptions, a special consideration was taken in order to improve their performance. Joints and terminations which form a critical part of the cable system are known as the weakest link and susceptible to failure due to many considerations related to design, installation and operational parameters. It is very important for network owners to know the most threatening source of failures in order to decide the direction of improvement. This paper shows field experience of National Grid SA with MV heat shrink cable accessories over five years and introduces a fault analysis method to improve their performance by learning from fault experience. Key words Fault Analysis, Cables Accessories, Heat Shrink, Medium Voltage JICABLE15_0045.docx Hybrid energy transfer lines with liquid hydrogen and superconducting cable - first experimental proof of future power lines. V.S. VYSOTSKY, A.A.NOSOV, S.S.FETISOV, G.G.SVALOV (1), V.V. KOSTYUK (2), E.V. BLAGOV (3), I.V. ANTYUKHOV (4), V.P. FIRSOV (4), KATORGIN B.I.(4), RACHUK V.S. (5) 1 - Russian Scientific R&D Cable Institute, Moscow, Russia 2 - Russian Academy of Science, Moscow, Russia 3 - INME RAS, Moscow, Russia 4 - Moscow Aviation Institute - Technical University, Moscow, Russia 5 - KBKhA, Voronezh, Russia The transfer of high power flow over long distances will be the one of the major task for energetics in this century. Liquid hydrogen attraction is clear -- it has the highest energy content of any known fuel and when it's burned, the "waste" is water. It could be transferred via cryogenic tubes like other cryogen liquid. Moreover, with the use of “gratis” cold to cool a superconducting cable an extra electrical power can be delivered with the same line. One of solutions is to use DC power cables made of cheap MgB2 superconductor with single phase liquid hydrogen as a cooler and energy carrier. The team of Russian researchers developed and tested the two first in the world prototypes of the future hydrogen and superconducting energy transport systems. Two systems with 10 m length (in 2011) and 30 m length (in 2013) has been developed and tested. The first system with 2.5 kA cable and outer diameter ~80 mm could deliver ~30 MW of chemical energy by liquid hydrogen and ~ 50 MW of electrical power at 20kV and 2.5 kA, i.e. ~80 MW in total. The second system with diameter ~120 mm underwent high voltage test at 50kV DC and could deliver ~55 MW of chemical energy by liquid hydrogen and ~ 75 MW of electrical power at 25kV and 3 kA or ~130 MW of power in total. Details of hybrid energy transport lines and their test results are presented. JICABLE15_0046.docx A study on the chemical & structural changes of thermally aged XLPE cable insulation by FTIR and thermal analysis techniques Burjupati NAGESHWAR RAO (1), 1 -Central Power Research Institute, Bangalore, India, nagesh@cpri.in Electric Power Systems comprises a large number of power cables which are quite expensive. These cables and their accessories, which are subjected to various kinds of stresses during their service life undergo ageing and deterioration of insulation and hence lead to forced outages. Forced outages are of serious concern and are not economical. Ageing processes are complex in general and take place under different stresses simultaneously or sequentially. Thermal ageing is a chemical process like molecular decomposition and oxidation of organic materials. Over the past a few decades, the progressive deterioration of extruded cable insulation is assessed through non destructive techniques like measurement of Insulation Resistance, Dissipation factor, Loss angle & capacitance, partial discharge (PD) measurements mainly for trend analysis. However, determination of remaining life becomes the most difficult part due to lack of well defined deterioration models, lack of adequate data, and multiplicity of failure mechanisms. The study of structural and chemical changes that insulation undergoes during ageing is scanty and not fully explored which is absolute necessity to understand the deterioration mechanisms. As suggested by CIGRE Working group 33/15.08 there is a need to apply physical / chemical tools like structural, morphological and spectroscopic procedures which do not appear to be in use for dielectric diagnosis. Such an approach seems to be desirable for understanding the ageing mechanisms in a more comprehensive way and to increase the reliability of measurements. In this paper an attempt has been made to understand the structural and chemical changes that XLPE insulation undergoes during thermal ageing. Techniques like Fourier Transform Infrared (FTIR), Differential Scanning Calorimeter (DSC), Thermo Gravimetric Analysis (TGA), Thermo Mechanical Analyser (TMA) and Scanning Electron Microscope (SEM) were used to understand the chemical and structural changes. XLPE cable samples taken from long length distribution and transmission cables were used in the present study. The samples were subjected to accelerated thermal ageing at three different temperatures as per the international guidelines. Experiments were conducted on fresh and aged samples in order to study the effect of thermal ageing on the chemical changes which take place in the XLPE material. The structural changes observed are the formation of carbonyl groups. The effect of ageing on the melting peak temperature Tm, melting enthalpy were examined using thermo analytical technique. The results showed that thermal ageing at temperatures above the melting temperature of XLPE has a great effect on the material structure. The decomposition temperatures of the specimens though are not that distinct from the normal curves; the derivatives precisely show the peaks at which decomposition is occurring. SEM Pictures showed a significant difference in surface morphology between sound and aged cable XLPE samples. Key words Dielectric diagnosis, XLPE insulation, FTIR, chemical changes, structural changes JICABLE15_0047.docx Long term qualification of XLPE electrical insulation systems for offshore deep water cables Hallvard FAREMO (1), Karl Magnus BENGTSSON (2), HanskVARME (2) 1 - SINTEF Energy Research, Norway 2 - Nexans Norway AS, Norway There is an increasing demand for subsea electrical power transmission in the oil- and gas industry. Electrical power is mainly required for subsea pumps, compressors and for direct electrical heating of flowlines. The majority of subsea processing equipment is installed at water depths less than 1000 meters. However, projects located offshore Africa, Brazil and in the Gulf of Mexico water depths of 3000 meters are reported. Hence, Nexans Norway and SINTEF Energy Research initiated a long term development programme to qualify deep water XLPE power cable. The long term test programme was mainly based on ANSI / ICEA S-97-682-2007. Some adjustments related to the high hydrostatic test pressure (300 bars) were; however, required. A 7.2kV XLPE test cable was manufactured and installed in a large hydrostatic test vessel at 45°C and 300 bars. The cable samples were stressed with an electrical test voltage of 17kV; corresponding to an average electrical stress of 5.9kV/mm. Evaluations are performed after 120, 180, 360 and 900 days of hyperbaric ageing. Nexans Norway has a long and proven experience of delivering wet designed power cables i.e. without a metallic water barrier. After the hydrostatic ageing of the model cable at 300 bar hydrostatic pressure the cables were tested in order to determine the electrical properties of the insulation system. I n addition, water tree analysis were performed after the hydrostatic ageing. Contact: Hallvard.Faremo@sintef.no JICABLE15_0048.doc The impact of water filling of cable conductors during accelerated water tree ageing tests Sverre HVIDSTEN (1), Hallvard FAREMO (1), Svein Magne HELLESOE (1) 1 - SINTEF Energy Research, Trondheim, Norway, sverre.hvidsten@sintef.no Modern cables for the distribution and transmission grid have normally an axial water tight design including strand sealing systems avoiding ingress of liquid water in the conductor. The main purpose of this paper is to discuss the consequence of doing accelerated ageing with liquid water in the conductor for modern designs. The cable used for testing is consequently not the same as that for service. The local conditions close the conductor screen can have a significant impact on the water treeing. This will be discussed in this paper with special attention to cases with water in the conductor. Modern cable design with strand filling material (powder/compound) will likely not have liquid water present in the conductor during service. By water transport calculations it can be shown that liquid water in the conductor causes rapid water saturation in the insulation when the cables are subjected to a uniform temperature. However, the subsequent corrosion of Al strands by time causes initiation of rapid growing vented water trees from the conductor screen. This effect could as well be temperature dependent. Yet no such effect is observed for cables with Cu conductors. The combined effect of liquid water in the conductor and a temperature gradient (due to current loading) results in a nonsteady water diffusion into the insulation. Then a significant water condensation occurs in the middle of the insulation strongly enhancing the water tree growth. Acceleration of water treeing with water in the conductor is therefore less relevant for modern cable designs with swelling powder/compound in the conductor. JICABLE15_0049.doc A study on state assessment method of power cable system to be upgraded. Biao Yan (1), Li Zhou (1), Jie Chen (1), Jingjun Wang (1) 1 - Jiangsu Electric Power Company Research Institute, Nanjing, China, fengchuiguolai@126.com, zl_jtt@163.com, 2008840320@163.com, 15105168881@163.com To change the power transmitted by power cable system, three variables can be changed in the power formula: the voltage level, the current rating and the power factor. In order to transmit more power, one way in an existing power cable system is to raise the running voltage, in this way, the insulation performance of the existing system should be re-checked. From the statistics angle, this paper propose a state assessment method to evaluate the feasibility of raising the running voltage in an existing power cable system, this method takes into account the running environment, service ages, failure history and structure etc. of this existing power cable system. A large number of running power cables were selected for insulation performance evaluation test, results of stepwise voltage breakdown tests are in consistent with its state assessment. JICABLE15_0050.docx Development of a new liquid antioxidant for stabilizing XLPE compounds or for direct peroxide injection process. Jonathan HILL (1), Siren TAN (1), Chris RIDER (1), Denis LABBE (4) 1 - Addivant Tenax Road, Trafford Park, Manchester, M17 1WT, UK.2 Jonathan.Hill@addivant.com.,Siren.Tan@addivant.com, christopher.rider@addivant.com 2 - P&M Cable Consulting LLC WTC II Geneva Switzerland dlabbe@pm-ch.com To satisfy the wire and cable markets increasing demands for improved performance and greater reliability, raw material suppliers must constantly innovate and develop new solutions. This is especially true for medium and high voltage applications where the trend for thinner wall insulation, while at the same time maintaining the same electrical gradient, requires the use of extra clean materials, whether polymers or additives. The need for greater performance and cleanliness also applies to the antioxidants used in these applications. The new liquid antioxidant developed fulfils these requirements. The new levels of performance and cleanliness provide exceptional purity enabling greater reliability and extending the cable longevity in service. This paper will present the technical data generated in the laboratory as well as data from cables that have been produced by the so called DPI (Direct Peroxide Injection) process. As a novel antioxidant, it shows significant stability and compatibility with commonly used peroxides. There is no segregation, no discoloration, and no premature reaction before use, hence allowing preset mixtures to be used. The remarkably low freezing point that goes well below zero degree°C, also allows greater handling and processing flexibility for cables producers. Contrary to commonly used antioxidants, it provides sufficient scorch protection whilst increasing the crosslinking speed. The new solution does not interact with the peroxide during crosslinking which enables the cable maker to either marginally increase his CV line speed or to reduce the peroxide content hence providing increased productivity, cost savings along with peroxide by products reduction. JICABLE15_0051.doc DC electrical conductivity in LDPE-based nanocomposites Anh T. HOANG (1), Love PALLON (2), Dongming LIU (2), Carmen COBO SANCHEZ (2) anh.hoang@chalmers.se, lovep@kth.se, donliu@kth.se, carmencs@kth.se Ulf W. GEDDE (2), Stanislaw M. GUBANSKI (1), Yuriy V. SERDYUK (1) gedde@kth.se, stanislaw.gubanski@chalmers.se, yuriy.serdyuk@chalmers.se 1 - Chalmers University of Technology, High Voltage Engineering, SE-412 96 Gothenburg, Sweden 2 - KTH Royal Institute of Technology, School of Chemical Science and Engineering, Fibre and Polymer Technology, SE-100 44 Stockholm, Sweden Nanofilled materials have become increasingly popular as insulation materials in various electrical devices owing to the great advancement in their insulation performance. In the case of high voltage direct current (HVDC) cables, where the development of new insulating materials that are expected to operate at enhanced electric stresses is urgent, the use of nanocomposites opens for new design solutions. The objective of this work is to study the effect of nanofillers on dc conductivity in materials for such systems. Low-density polyethylene (LDPE) filled with nanoparticles of aluminium oxide (Al2O3) and magnesium oxide (MgO) up to 3 wt% were prepared. The nanoparticles were manufactured and were either additionally coated using hydrophobic silanes or by grafting hydrophobic polymethacrylate chains onto the nanoparticles or used without any surface modification. After mixing the particles with LDPE, scanning electron microscope (SEM) images of the resulted composites were obtained showing good dispersion of nanoparticles in the polymer. For electrical conductivity measurements, samples were manufactured as films of 80 µm thick and the polarization current was measured by standardized procedure using a three-electrode system at temperatures of 40 and 60°C and an electric stress of 32kV/mm. A pristine LDPE material was used as a reference. The measured electrical volume conductivity of the nanocomposites appeared to be approximately one order of magnitude lower than that of the reference material. In addition, the decrease was proportional to the concentration of the nanofillers. The effects of both types of nanofillers as well as coating treatments on material properties were compared. The reduced conductivity of both types of nanocomposites could be attributed to the introduction of deep traps in the interfacial region, resulting in accumulation of immobile charge carriers and reduction of the electric field in vicinity the of electrodes that eventually lowers injected currents. The reduced electrical conductivity is therefore one of the indicators suggesting that nanofilled polyethylene is a potential candidate for use in the new generation of HVDC cables operating at higher electrical stresses. JICABLE E15_0052.do ocx Enha anced medium m voltage e cable ratings by imp proving cable trenc ch desig gn and th hermal c conditio ons Sander M MEIJER (1), Frank DE WILD W (1), Abd dulla Ahmad Mohd AL AGHBARI (2)), Maryam AL L NEAIIMI (2), Muha annad Rizik Mahmoud A ASHAAR (2), Mohd Arf Ali ALABBAD DI (2) 1 - DNV GL, Arnhem m, The Netherlands, sande er.meijer@dnvgl.com , frrank.dewild@ @dnvgl.com 2 - DEW WA, Dubai, Un nited Arab Emirates, Abd dulla.AlAghba ari@dewa.go ov.ae , Maryam.ALNeaim mi@dewa.gov.ae , Muhan nnad.Ashaarr@dewa.gov v.ae , Mohd d.Alabbadi@ @dewa.gov.ae e Due to increasing power p dema and, Dubai E Electricity an nd Water Au uthority (DE EWA) is experiencing higher lo oading of th heir medium m voltage (M MV) cable network. n Exp pansion of tthe cable ne etwork is restricted d mainly due e to space lim mitations in tthe city of Dubai. D Thereffore, other m means to incrrease the current rrating of the MV M cable ne etwork are re quired. The cab ble current ra ating depend ds on differe ent aspects, such as the e cable arranngement in the t cable trench a and the soil surrounding the cables.. In particula ar, the value e of the therrmal resistivity of the backfillin ng material is i of utmost importance . DEWA and DNV GL have investiigated possibilities to reduce tthe value of o the soil th hermal resisstivity to 1.0 0 km/W or less by usinng special backfilling b materialss. Moreover,, the backfilling material should be made m from lo ocal availablle materials. This will result in a significantt improvemen nt in medium m voltage cab ble ratings. This con ntribution de escribes the e performed soil investiga ations, the optimized cable tre ench arrangem ment and la ay-out. It als so describess the necessa ary quality control and a assura ance measure es to en nsure prop per fabrica ation, transporrtation and installation of o the backffilling material.. As expeccted, it is shown s that the presence e of moisturre and the magnitude m off the dry density have an a importantt impact on n the magnitud de of the thermal resistivity. It was conclude ed that loca ally available crushed rock combine ed with red dune d sand, with a minim mum dry den nsity of 210 00 kg/m3 an nd 1% moissture content w will lead to a thermal res sistivity of aro ound 1.0 km/W W. Finally, an existing cable trench has been selected as s pilot proje ect to partly replace the e existing backfillin ng material by the prop posed backffilling materiial. Tempera ature measuurements ha ave been conducte ed for over one o year in a part of the ttrench with the original sand and in a part with th he backfill material.. The therma al influence of o the propossed backfilling material ha as been inveestigated, but also the stability and settling of the propo osed backfilliing material. After one year, sampless have been n taken in both parrts of the cab ble trench. It was conclud ded that the moisture co ontent was inn the order of 2% and no signifficant changes in the ma aterial itself o he temperatu ure measureements show wed lower occurred. Th values in n the backfill material co ompared to t he original material m whic ch confirms tthe improved d thermal conductivity of the ba ackfill material. JICABLE E15_0053.do ocx Impac ct of HV VDC Cab ble Conffiguratio on on Compass s Deviattion Sander M MEIJER (1), Roald DE GRAAFF G (1), Stephen HE EMPHILL (2)), Mick MCG UCKIN (2) 1 - DNV GL, Arnhem m, The Netherlands, sande er.meijer@dnvgl.com , ro oald.degraaff ff@dnvgl.com m 2 - Mutual Energy, Belfast, B Irelan nd, steph hen.hemphill@mutual-energy.com , m mick.mcguck kin@mutual-e energy.com The Moyyle Interconn nector betwee en Ireland an nd Scotland is a 500 MW W Dual Monoopole HVDC link. Due to four re ecent cable faults on the e Moyle Inte erconnector, all caused by b the same type of failu ure of the integrate ed return con nductor (IRC C) insulation,, Moyle has examined three optionss to either re eplace or remove tthe need for the low volta age integrate ed return con nductors: 1. a application of o one of the e HV conducctors as LV return condu uctor, achievving a single e 250MW m monopole (a as an emerg gency fall ba ack in the ev vent of simultaneous LV V cable faults s on both p poles); 2. iinstallation of o new sepa arate LV Ca ables to rees stablish ((using the exxisting HV an nd new LV); 500 MW dual monopole operation o 3. a amendment of the conve ertor station ccontrols for bipole b operattion, at 500M MW. Besides many otherr aspects, th he impact off such config guration cha ange on the magnetic fields was assessed for each of o the above options. Thiss contributio on discusses the implicattion of those changes to EMF characteristics regardin ng onshore and offsho ore legislatio on and reguulations, in particular compasss deviation. Because off the speciall coaxial des sign of the HVDC cablee with the in ntegrated onductor, th return co he magnetic fields inducced by the current in th he high-voltaage and low w voltage conducto ors mostly cancel c each other. How wever, by ch hanging the cable syste m configura ation to a situation n with a new w external re eturn conducctor, theory shows s a pottentially signnificant chang ge in the magneticc fields, depe ending on th he exact loca ation of the new n return co onductor in re relation to the e existing high volttage conducctor. In partic cular in lowe r waters, this s can result in significannt compass deviation. d To verifyy the theore etical results s, Mutual En nergy decided to condu uct a subseea ground trruthing in temporary bipole co onfiguration. Results of tthis ground truthing will be describeed and discussed. A close ma atch between n theory and measured vvalues was observed, see e figure below w. Finally, tthe installatio on of new se eparate LV ccables was selected s as the t preferredd solution forr reasons of redu undancy and d transmiss sion capaci ty. With th he validated d theoreticaal models, different configura ations were investigated d to optimize e the locatio on of the LV cables. Of course, the distance between n the existing g HV and new w LV cable p plays a significant role. Therefore, T coompass devia ations for different realistic sccenarios werre calculated d, taking intto account the presencee of rock dump, the accuracyy limits of su ubmarine cable placeme ent, and whiile avoiding the risk of ddamaging the e existing cables. T The resulting g solution will w be discusssed with the relevant agencies a to gget approval for final reconfigu uration and operation o of the Moyle In nterconnectorr. JICABLE15_0054.docx Temperature and Electric Field Dependence of XLPE MV Cable Joint Stress Control Sleeves Henrik ENOKSEN (1), Sverre HVIDSTEN (1), Mai-Linn SANDEN (2), Frank MAUSETH (2) 1 - SINTEF Energy Research, Trondheim, Norway, henrik.enoksen@sintef.no 2 - Norwegian University of Science and Technology, Dept. of Electric Power Engineering, Trondheim, Norway On-site measurements by dielectric loss tangent (tan δ) as a function of voltage and frequency is wellestablished for assessing the condition of water treed medium voltage XLPE cable insulation. However, if the cable section also consists of e.g. joints with a high tan δ, the interpretation of the measured tan δ could be challenging and even lead to an erroneous assessment, e.g. stating that the insulation is severely water treed. In Norway it has been observed that many XLPE cable sections installed in the 80's has one or several heat shrink joints with a very low insulation resistance. Laboratory examinations show that such joints have likely experienced excessive overheating during service due to bad metallic conductor connectors. This paper will focus on the temperature and electric field dependence of the time domain dielectric response of a stress control sleeve commonly used as a part of the MV heat shrink joint design in Norway. The polarization and depolarization currents for an unused sleeve are measured at temperatures up to 150°C. DSC measurements will be performed to determine if the material experiences phase transitions in the measured temperature regime. The polarization and depolarization currents for the virgin stress control sleeve have no field dependence in the low field regime below service stress. Further work will include measurements at higher fields and temperatures close to that experienced during overheating. The results from these measurements will be reported and included in the paper. JICABLE15_0055.docx On-site Condition Assessment of XLPE MV Cable Joints by Using an Insulation Tester Jan Tore BENJAMINSEN (1), Henrik ENOKSEN (1), Sverre HVIDSTEN (1) 1 - SINTEF Energy Research, Trondheim, Norway, Jan.T.Benjaminsen@sintef.no Measuring the dielectric loss tangent (tan δ) as a function of voltage and frequency is a wellestablished method to assess the condition of medium voltage XLPE cable insulations containing water trees. In Norway it has been observed that many XLPE cable sections with heat shrink joints have a very low insulation resistance. If the cable section assessed contains such joints, the resulting high tan δ values may lead to erroneous conclusions, typically that the insulation is heavily water treed. Laboratory examinations have shown that these joints most likely have experienced excessive overheating during service. This paper presents on-site time domain dielectric response measurements on Norwegian XLPE MV cables from the early 1980's. All the selected cables have joints with a low insulation resistance. The main purpose of this paper is to examine if the dielectric response of cables with low resistivity joints depends on the service conditions. This includes the load history, the ambient temperature and weathering conditions. This information is important as it could have an impact on the development of the diagnostic criteria. It has been shown that both the polarization and depolarization currents of the low resistance joints studied in the laboratory are e.g. voltage dependent. The data obtained on-site will be compared with the laboratory measurements. These results will be used to finally develop a simple method for assessing the condition of cable systems with critical joints by using an insulation tester. JICABLE15_0056.docx How to perform a pre-qualification test - interpretation of the standard Edwin PULTRUM (1), Wouter SLOOT (1), Cor EILANDER (1), Alphons BAAS (1), Gu BIN (1) 1 - KEMA Laboratories, Arnhem, the Netherlands, edwin.pultrum@dnvgl.com With the first edition of IEC 62067 in 2001 the pre-qualification test (PQ Test) was introduced in the cable standards of IEC. The background for including this new test is given in this first edition of IEC 62067: “in order to gain some indication of the long term reliability of a cable system, it is necessary to carry out a long term accelerated ageing test. This test […] is to be performed on the complete system comprising the cable, joints and terminations in order to demonstrate the performance of the system.” The test subjects cable systems consisting of highly stressed cable designs and their accessories to heating cycles under voltage. The cable system is usually installed under various laying conditions. During this test the cable system has to endure various environmental conditions which may vary, e.g. summer, winter, dry, wet, etc. The pre-qualification test requires the voltage to be applied during one year. During this year the cable system installed must be subjected to 180 heating cycles each with a minimum duration of 24 hours. This leaves quite some room for interpretations and consequently different ways to execute this test, resulting in different outcome depending on the choices made at the start of the test. One could choose to apply 48 hour heating cycles. This results in a nice distribution of all heating cycles during the one year voltage application. However, this is not corresponding to the actual situation where the load has a 24 hour pattern. When choosing to apply 24 hour heating cycles, should the heating cycles be applied during the whole year of voltage application, i.e. 365 heating cycles, or is it allowed to stop after 180 heating cycles have been applied? If only 180 heating cycles are applied, should the heating cycles take place during the first half year of the test or should it be distributed following the seasons? Next to this, during the heating of the cable system, the conductor temperature should reach 90-95°C. Different laying conditions result in different thermal environments and consequently different conductor temperatures with the same conductor current and obviously, this must be accepted. But what (sheath) temperature difference between the various laying conditions is acceptable? This lack of guidance in the standard results in different ways this important test is being executed at the various test places, either at the manufacturer or at independent laboratories worldwide. KEMA Laboratories have performed this test since the first edition of IEC 62067 at their test facility in Arnhem, the Netherlands, and have witnessed this test at various manufacturers and test facilities world-wide. This showed us that many different interpretations exist as illustrated above. Based on our experience, this paper will give a guideline to execute this pre-qualification test in accordance with the requirements given in the standard and in line with the background for including this test in the standard. This will avoid the current situation where the result depends on the choices made before starting the test. JICABLE15_0057.docx Watertight Cable Designs in Hydropower Generation Plants Børre SIVERTSVOLL and Terje RØNNINGEN (1), Hallvard FAREMO and Jens Kristian LERVIK (2), Kåre HØNSI and Rolf WILNES (3), Ole Kristian JACOBSEN and Hans Lavoll HALVORSON (4) 1 - Siemens AS 2 - SINTEF Energi AS, Hallvard.Faremo@sintef.no 3 - Statkraft Energi AS 4 - BKK Nett This paper discusses the screen currents induced in the aluminium laminate of 24kV watertight XLPE cables installed for the generators of a Norwegian hydropower generation station. Consequences and how to improve the cable system will also be discussed. Repeated faults on a heavily loaded new cable system resulted in serious doubts about the performance and life expectancy of the installed system. At times during the project, a full replacement with new cables was seriously discussed. The costs involved would; however, be substantial. Hence a team consisting of parties involved and SINTEF Energy Research; was set up with the aim to try to come up with possible alternative and reliable solutions. The team thoroughly evaluated available information and background information, discussed with both cable and cable accessory manufacturers before a new solution was introduced. The cable system has worked as expected for more than two years after the new solutions were implemented. JICABLE15_0058.doc Dynamic Cable Installation for Fukushima Floating Offshore Wind Farm Demonstration Project Kiyotomo YAGIHASHI (1) Yuji TATENO (1), Hiroyuki SAKAKIBARA (2), Hiroki MANABE (2) 1 - VISCAS Corporation, Tokyo, Japan, k-yagihashi@viscas.com, yu-tateno@viscas.com 2 - Furukawa Electric Co., Ltd., Tokyo, Japan, manabe.hiroki@furukawa.co.jp, mr960211@mr.furukawa.co.jp Furukawa Electric Company and VISCAS Corporation have proceeded with a Fukushima FORWARD Project (FF project) as one of the commissioning manufacturers of the Ministry of Economy, Trade and Industry. This paper reports the development condition of the power transmission system, mainly the development of a high voltage dynamic cable, which is considered as an essential technology. The FF project consists of a 1st stage (2011-2013) and a 2nd stage (2014-2015). Figure 1 illustrates the transmission and substation system. A behavior of dynamic cables subjected to under-water rolling caused by the steadily wave movement is different from that of the static submarine cables. Therefore, a development point is the improvement of a fatigue withstands property. For a practical application of riser cables, a target is to achieve the similar endurance life of a floating body or of a wind turbine. As the dynamic cable, a fixed wave condition and a floating body’s rolling condition are needed for the riser cable design at first for external conditions. A static behavior analysis, a dynamic behavior analysis and a fatigue analysis are in turn conducted with combinations of the various parameters and the shapes for a riser cable under above conditions. The analysis and feedbacks are reiterated and finally the most suitable submersible shape design and its detailed riser cable design are defined. It is essential for a conceptual construction of the submarine cable to meet the specification in accordance with the electrical equipment technical standards and for its electrical and mechanical characteristics to satisfy JEC-3408, CIGRE TB 490 and CIGRE Electra No.171. Based on the previous findings, the riser cable construction is defined as shown in figure 2. The cable has double layers of strand armor wires twisted in opposite directions in order to prevent cable torsion. The transmission system was installed in order of submarine cable, riser cable and submarine joint. The 66kV riser cable was installed form the substation to the jointing point with submarine cable. After installing the riser cable, the submarine joint was constructed on the vessel with the submarine cable which had been installed. The 1st stage of the FF project was successfully completed in 2013 and it is already under operation. This research is carried out as a part of Fukushima floating offshore wind farm demonstration project funded by the Ministry of Economy, Trade and Industry. The authors wish to express their deepest gratitude to the concerned parties for their assistance during this study. Shore Switching Station & Shore System Grid Transmission Line 22kV Windmill & Semi-submersible Floating Structure Floating Substation (66kV/22kV substation / observation tower) Conductor Conductor screen XLPE Insulation Insulation screen Metallic screen Metallic Sheath Inner jacket (PE) Filler Intermediate Buoy 66kV Submarine Cable 66kV Riser Cable Intermediate Buoy Intermediate Buoy Bedding Armor Outer jacket (PE) 22kV Riser Cable Optical fiber unit Submarine Joint Fig. 1: Transmission and substation system in FF project Fig. 2: Structure of 66kV riser cable JICABLE15_0059.docx Degradation Rates in High Voltage Subsea Cables with Polymeric Water Barrier Designs Torbjørn Andersen VE (1), Sverre HVIDSTEN (1), Jorunn HØLTO (1), Knut Magne FURUHEIM (2), and Hanna HEDSTRÖM (2) 1 - SINTEF Energy Research, Norway, torbjorn.ve@sintef.no 2 - Nexans Norway AS, Norway Water treeing is one of the main degradation mechanisms in high voltage cross-linked polyethylene (XLPE) cables exposed to water. High voltage subsea cables are normally equipped with a metallic water barrier to keep the insulation dry. In some cases this may not be advantageous e.g. when the cable is subjected to substantial dynamic mechanical stress. In the absence of metallic water barriers, the moisture content in the insulation will rapidly increase as water diffuses into the system. Water tree initiation does normally not occur at relative humidity values (RH) lower than approximately 70%. However, the water tree growth rate is affected by the RH above this level. Therefore, limiting the rate of increase of the relative humidity in the insulation by a smart designed polymeric sheath system, the lifetime of a cable will be significantly extended due to reduced water tree growth. The main purpose of this paper is to demonstrate this model by presenting numerical calculations of water ingress in a semi-conductive wet submarine cable design and results from water tree growth rate experiments at different RH in extruded 12kV model XLPE cables. The first part of the paper presents results from numerical calculations of water ingress in subsea XLPE cable with a two-layered polymer sheath design. The polymeric outer sheath system was found to increase the time to 70% RH by over eighteen years at 20°C compared to the same cable without any sheaths. This means that no water tree initiation will occur during this time. In addition, the time to 99% RH was increased by over eighty years by including the outer sheath system. The water tree growth rate is likely inhibited during this period, causing an additional lifetime expectancy increase. The effect of the reduced RH on water tree growth rate is studied in the second part of the paper using 12kV model XLPE cables. The cables were aged for 6 months at 3U0 (18kV), in a controlled humid air atmosphere. In total, five different levels of relative humidity were used. The samples were preconditioned for 5 months in order to ensure a constant distribution of moisture in the insulation. JICABLE15_0060.docx Influence of expansion on electric field distribution of stress cones for high voltage cable accessories Stefan ZIERHUT (1), Dr. Thomas KLEIN (1), Dr. Eckhard WENDT (1), Lutz ZÜHLKE (1) 1 - Strescon, Esslingen a. N., Germany, stefan.zierhut@strescon.de, thomas.klein@strescon.de, eckhard.wendt@strescon.de, lutz.zuehlke@strescon.de Modern accessories for extruded HV and EHV cables commonly make use of premolded stress cones made from elastomeric materials. This is widely established because of many benefits, like easy installation and the possibility of routine testing all stress cones in the factory. A stress cone is made from insulating material on the outside and embeds a semi conductive layer or part, which is formed to create a field controlling contour. Silicone elastomers have won recognition in this field due to the good manufacturing properties and the outstanding dielectric performance. Computer aided calculation of the electrical stress in the accessory is used to determine the exact shape of the stress cone parts. At joints and outdoor terminations the stress cones have to be installed on the cable with considerable expansion in a defined range. This expansion creates the surface pressure that is needed to withstand the electrical field stress in the gap between stress cone and cable surface. By expanding the stress cone gets out of its original shape - the wall thickness is reduced and the deformation changes the outline of the semi conductive surface. Thus the original electrical field calculation is no longer valid. The electrical field stress is generally increased and the installed accessories may perform worse than calculated. Today cable systems tend to use higher voltages, which are often combined with comparative less insulation thickness. As a result of this some cables have a very high electrical field in the insulation that is straining the accessory field control system. At the same time the use of very large conductor cross sections is increasing, ever raising the electrical field in outdoor terminations. Consequently the stress cones have to be designed in an optimal way and it is sensible to consider the deformation effect. This paper describes an approach for this problem. The expanded outline of the surface contours are calculated by a simple method. This method is based on the assumption that the volume of the elastomeric part is not changed by expansion. The new surface contours are then used in the electrical stress calculation. Eventually the original contour of the stress cone is modified to give optimum performance after expansion. JICABLE15_0061.doc Development of Compact Designed 66/77kV Class XLPE Cable System Shinji MARUICHI (1), Koichi OONO (2), Masaya MOKI (2), Hiroshi NIINOBE (2) 1 - Viscas Corporation, 6, Yawata-Kaigandoori, Ichihara, Chiba 290-8555, Japan, s-maruichi@viscas.com 2 - Viscas Corporation, 4-12-2 Higashi-Shinagawa, Shinagawa-ku, Tokyo 140-0002, Japan, ko-oono@viscas.com, m-moki@viscas.com, hi-niinobe@viscas.com There are demands to replace 3-core SCFF cables operated in duct for more than 30 years. From view point of environmental stress free, these cables shall be replaced to XLPE cable in coming decades. However, it’s difficult to install the same size of XLPE cable in old duct for SCFF, due to difference in diameters. Therefore, there are needs to develop new products with same (or smaller) diameter as that of SCFF, and their accessories. This paper describes development activities of compact designed XLPE cable (which can be applied to existing duct) and accessories, mainly focused on electrical performance for 66/77kV class. Duct 3-core XLPE conventional 3-core SCFF 3-core XLPE compact designed Fig.1 Cable dimensions in duct 1. The design features of developed products The new 3-core XLPE cable has smaller diameter by 10 to 20% mainly by reducing insulation layer thickness. Joint has the latest design with cold shrink technology which is easy to assemble on site. As for termination, two types are arranged. One is contemporary design “Type-I” which consists of EPDM rubber cone and porcelain bushing with silicone oil inside. Another is new developed dry outdoor termination “Type-II” which uses hollow composite type bushing and silicone gel instead of silicone oil as insulating compound inside the bushing. 2. Electrical performance of developed products Electrical stress tests were conducted on compact XLPE cable whose insulation thickness was set to smaller value than target design value, for development purpose. The test result showed good performances. Subsequently, a loading cycle test on 600 mm2 compact designed XLPE cable system was carried out for 6 months based on JEC-3408 (Japanese domestic standard) to confirm long-term stability and reliability. Two types of outdoor terminations were arranged in the test circuit, too. The test results satisfied the requirements in accordance with JEC-3408. Compact 66/77kV XLPE cable and accessories have been designed. These cable systems can be installed into duct for old SCFF, with the same ampacity of existing SCFF. Excellent electrical properties were confirmed of requirement in Japanese domestic standard (JEC-3408). This system has been already qualified for commercial application and is expected to be used for 66/77kV class application in the near future. JICABLE E15_0062.do ocx Influe ence off the screen/a s armour permea ability in mag gnetic fields s genera ated by HV cablles F. Faria DA SILVA (1), Claus L. BAK (1), Th omas EBDR RUP (2) 1 - Aalbo org Universitty-Departmen nt of Energy Technology, Aalborg, De enmark, ffs@ @et.aau.dk, clb@ @et.aau.dk 2 - Energ ginet.dk, Fre edericia, Denmark, teb@e energinet.dk The insta allation of lon ng cables inc creased stea adily in recen nt years and this trend is expected to continue in the future. A topicc in need of further f resea arch, for diffe erent reasons s, is the maggnetic field generated g by cable es. One of the reasons is i the possib ble effects off the magnetic field in human and an imal health. Changes in the b behaviour off sea life ha as been reg gistered afte er the installation of suubmarine cables and differencces sources point p out for magnetic fie elds as the ca ause. A secon nd reason iss the overes stimation of the losses in submarin ne cables. S Several partties have measure ed these losses and verrified that the ey were low wer than expected. Differrent authors propose different reasons forr this, but se everal indica ate that the influence i of the armour in the magn netic field generate ed by the cab ble is the ma ain reason fo r the overesttimation. Res search is currrently being made by Aalborg University and a Energin net.dk for th he developm ment of new analytical fformulae capable an accurate e estimation of o the losses s in submarin ne cables. Th his paper is one o in a seriies of severa al that will build the e path for the e new equations and thatt can also su upport other researchers in topics related with magneticc fields. Typicallyy, the magnetic fields are a estimated d using FEM M software, as analyticaal equations s are too complexx and accura ate simplified formulae ha ave yet to be e developed. This paperr proposes to o present the mag gnetic field and a induced voltages/cu urrents, estim mated by means of FEM M, for severral cases (single-ccore cable, th hree-core cab bles, two cab bles, differen nt screen/arm mour thicknessses, etc…). The simulations are made for a large range e of frequenc cies, from DC C up to 10 kkHz, and forr different magneticc permeabilitty of screens s (for single-ccore cables)) and armourrs (for three--core cable). Screen’s relative p permeability different of 1 do not havve a practica al meaning, but the anallysis is helpfful for the developm ment of accu urate formula ae for the thre ee-core case e. Besides comparing the t results fo or the differe ent scenarios s, fitting apprroximation of the results, with the correspo onding fitting error, will also be provid ded with the magnetic m permeability, frrequency, cu urrent and geometrry as variable es. The obta ained resultss will help understandin u ng the reaso ons for the overestimatio o on of the los sses and indicate the aspects that should receive r more e attention in n the develop pment of new w analytical fo ormulae. JICABLE15_0063.docx Metal tape forming and welding as attractive alternative for shielding of MV, HV and EHV cables. Thomas KULMER (1) 1 - Rosendahl Nextrom GmbH, Pischelsdorf, Austria, thomas.kulmer@rosendahlnextrom.com A range of coverings for MV, HV and EHV power cables are already established on the market, including longitudinally applied AI/PE tape, extruded aluminium and lead. Some of these, however, do have limitations and no longer meet the high levels currently demanded by the market. Today’s cable designs and their requirements are changing due to the need for improved mechanical properties and environmental friendliness, together with the requirement for flexible production. Rosendahl’s metal tape-forming and welding technology, with or without subsequent inline extrusion to apply a final HDPE layer, offers increased product quality and range of applications . This, with its accompanying benefits, is the best replacement for less effective traditional technologies. Key words: Rosendahl Nextrom GmbH; Metal tape forming and welding; Shielding of HV and EHV cables; JICABLE15_0064.doc Electric field distribution in polyethylene insulation used in the electric cables affected by water trees in the presence of space charges. Madjid MEZIANI (1), Abdelouahab MEKHALDI (1), Madjid TEGUAR (1) 1 - Ecole Nationale Polytechnique, B.P 182, El-Harrach, Algeria, madjid_mez@yahoo.fr, abdelouahab.mekhaldi@g.enp.edu.dz, madjid.teguar@g.enp.edu.dz The extruded polymeric materials are largely used as insulation of electric cables. However, in a wet environment, the penetration of water inside the insulation can have an important role in the formation of the water trees. These defects represent a significant factor in the process of the electric degradation of polymeric insulation, induced by the modification of the permittivity of the insulation. The association of space charges to these defects can be the principal cause of the electric tree initiation, and then, the rupture of the polymeric insulation. So, many studies have been carried out for a better comprehension of the space charges generation in the polymeric insulations. This work was directed so far towards the study of the space charge characteristics under D.C current, while the study of the dynamics of the space charge and its impacts on the electric defects under AC current caused only one limited attention. Indeed the behavior of space charge in the water tree under AC current is still badly understood. To understand the mechanism of displacement of this space charge in the presence of defects in polymer, an evaluation of the electric distribution of field is essential. The aim of this work is to determine the distribution of the field in polyethylene insulation used in the medium and high voltage cables, affected by water trees in the presence of space charges. In our study, we chose the model of vented tree, with homogeneous electric properties (permittivity and conductivity). We considered the case where these trees develop starting from the two semiconductor layers, interior and exterior of the polymer insulation. The results of investigation showed that the distribution of the field is uniform in the insulation in absence of any defect. However, when the insulation is affected by water tree, the field and the equipotential lines show more divergence compared with the case of pure dielectric. This non uniform variation of the field and equipotential lines which becomes apparent on the insulation-defect interface depends on the length as well as the position of the water tree compared to the conductor. Furthermore, the accumulation of the space charges induces a significant variation of the electric field close to the two semiconductor layers. Consequently, the electric field decreases in a remarkable way in the vicinity of the interior semiconductor layer while it increases significantly in the vicinity of the external semiconductor layer. Moreover, we noticed a considerable decrease of the equipotential lines in the volume of the insulation compared to the case where there are no space charges. We also noted that this distribution of the field depends on the quantity of space charges accumulated and their dynamic movement in the insulation with defects. Key words: Electric cables, polyethylene insulation, water trees, electric field, space charges. JICABLE15_0065.docx System Impedances for Power Cable Umbilicals Kristian Thinn SOLHEIM, Jens Kristian LERVIK (1) 1 - SINTEF Energy Research, Trondheim, Norway, kristian.solheim@sintef.no, jens.lervik@sintef.no The demand for electric power in the oil and gas sector is increasing as processing systems are moved subsea. These systems are supplied by high voltage cables concealed in a special designed umbilical together with hydraulics lines, service lines, injection systems, fibre optics, communication cables and low voltage supply cables for instrumentation and control. Typical loads are variable speed drives operating at frequencies varying from 50 to 200 Hz. As the umbilicals are exposed to large mechanical static and dynamic forces during installation and operation, proper armouring (steel reinforcements, carbon fibre etc.) is required. For designing the electrical system, the characteristic electrical properties of all elements at relevant frequencies are required. For the power circuits, the phase impedances (positive, negative and zero sequence) of each power circuits are needed to calculate impedance asymmetry related to motor acceptance levels, grounding currents, corrosion issues and leakage currents. For the remaining components, induced currents and voltages are of importance. Some of the fundamental values may be found in datasheets, but these are often IEC-specifications. The accuracy of these values is therefore questionable. Experiences from project work show that the required values may be calculated accurately using electromagnetic 2D numerical software if correct input values are used and the influence of armouring (especially steel) and internal twisting are included properly. 3D models may incorporate twisting, but several simplifications are often implemented as these models tend to be large and complex. Measurements are therefore needed to acquire accurate data for calibration of the utilized model. A proprietary measurement method and plan providing all relevant electrical data and properties have been developed. This includes measurements of per phase impedances and induced voltages and currents for relevant grounding conditions. An important issue is how the parameters depend on different operation conditions (applied voltage, current and frequency), grounding, temperature and twisting conditions. JICABLE15_0066.doc Use of aluminium conductors in submarine power cables Thomas WORZYK (1), Sonny LÅNGSTRÖM (1) 1 -ABB AB, High Voltage Cables, Karlskrona, Sweden, thomas.worzyk@se.abb.com, sonny.langstrom@se.abb.com The majority of installed submarine power cables have copper conductors. While it is widely acknowledged that power cables with aluminium conductors are less expensive than copper cables and this paved the road for a widespread use in underground power applications, some utilities are reluctant in choosing aluminium conductors for their submarine cable projects. Corrosion, mechanical stability and lightweight-related issues are usually invoked as argument against aluminium conductors. In spite of these perceived drawbacks many minor and some notable large submarine power cables with aluminium conductors have been installed successfully. This paper gives a short review of the present use of aluminium conductors for underground and submarine cables. This paper demonstrates the opportunities and limitations of aluminium conductors for submarine cables. It identifies aluminium properties that are relevant for submarine power cable conductors. Mechanical aspects and sea bottom stability of aluminium cables are addressed. From the analysis of relevant properties it is evident that the suitability of aluminium as a conductor material is different over the range of different submarine power cables. Experiences from one type of cables cannot easily be transferred to other types. It is explained why the corrosion processes that have occasionally been observed in low and medium voltage underground cables are not relevant for modern submarine cables. Aluminium submarine cables and the equivalent copper cables are compared with respect to weight, volume and logistics. As expected, aluminium cables are lighter but larger in diameter than their copper equivalents. For high-voltage submarine cables involving a lead sheath the differences are surprisingly small. In most cases the choice between aluminium and copper cable has no or little influence on the number of cable laying campaigns. The tensional strength of welded aluminium conductors and their welded joints has been measured and found suitable for single-layer armored aluminium submarine cables for 150 m water depth or more. Aluminium cables with double-layer armoring have been used for very large water depth. Accessories for aluminium cables deserve special attention; lack of knowledge and poor engineering have caused contacting problems in the past. If some basic principles are taken into account the jointing and termination of aluminium conductors can be managed reliablely. Aluminium conductors weigh only about the half of copper conductors with equivalent transmission capacity. Combined with a lower unit price of aluminum on the metal market than copper, this leads to considerable economic advantages of aluminium cables over copper cables. The characteristics of a few important submarine power cables (both HVDC and 3-core) with aluminium conductors are presented. JICABLE E15_0067.do ocx Qualiification n of an extruded e d HVDC cable system s a at 525kV V Anders G GUSTAFSSO ON (1), Marc c JEROENSE E (1), Hosse ein GHORBA ANI (1), Tobiaas QUIST (1), Markus SALTZER R (1), Andrea as FARKAS S (1), Fredrik AXELSSON N (2), Vincentt MONDIET (2) 1 - ABB AB, High Vo oltage Cables s, Karlskrona a, Sweden, anders.h.gus a tafsson@se .abb.com, marc.jeroense@sse.abb.com, hossein.gho orbani@se.ab bb.com, tobia as.quist@see.abb.com, markus.ssaltzer@se.a abb.com, and dreas.farkass@se.abb.co om 2 - ABB AB, Kabeldo on, Alingsås, Sweden, fre edrik.axelsso on@se.abb.c com, vince ent.mondiet@ @se.abb.com m Extruded d HVDC cab ble systems represent a field for which w there are a high exppectations on o further developm ment of the technology to t enable futture cost red duction in po ower transmiission of larg ge power over long distance. Since S the firrst introductio on of extruded HVDC ca able systemss in 1997 the e voltage level hass increased fast from 80kV to 320kkV, and therre is no obvious upper llimit to the insulation i technolo ogy. The 320 0kV level is enabling e a trransmitted power p of abo out 1000 MW W in a bipolar system. During 2 2014 a new highest leve el at 525kV for a compllete cable sy ystem includding accesso ories was launched d. In Jicable 2011 the challenges and opportu unities with different insulation mateerial conceptts for the cable we ere described d. Cross-link ked materialss with and without fillers as a well as theermoplastic materials were invvestigated. The T solution selected for the 525kV level is based on a newlly developed d material system combined with w an ad dopted cable e manufactu uring techno ology. Expeeriments ha ave been performe ed using a va ariety of test samples ran nging from plates p to mod del cables annd full-scale cables. A major drriving force has h been to achieve a a hig gher resistiv vity of the ins sulation comppound. The non-filled XLPE insulation syystem implied that w well-establishe ed procedu ures for quuality contro ol during manufaccturing could be used. The pre--fabricated jo oint is based on EPDM ccompounds including a non-linear fielld-controlling g material in order to govern th he DC stress. The flexible e factory join nt for creating g long lengthhs in the factory is as well bassed on estab blished techn nology. The tterminations are oil-free and insteadd gas-filled (S SF6) with composiite insulatorss based on ea arlier develo pments for HVDC H bushin ngs. The full sscale cable system s testin ng is perform med according to CIGRE Technical Brrochure No. 496. The two main n parts in the e qualification n process arre the prequa alification (long term) testt at 1.45 x 52 25kV and the shorrter type testt at 1.85 x 525kV. Two ttype tests ha ave been performed withh successful result as well as a passed one e-year pre-qu ualification te est. The 525 5kV extruded d DC cable system s can transmit at least 50% more m power oover longer distances d than the e 320kV extruded DC system. The h higher voltage level enab bles the conssiderably low wer cable weight p per installed megawatt (M MW) of trans mission capa acity. The tra ansmitted poower will reach above 2 GW through one pair of cables depending o on conductorr area and ty ype. JICABLE15_0068.doc 138kV Insulated Cable System for Temporary Connection of Transmission Lines and Substations. Gustavo SILVESTRE (1), Sérgio CAPARROZ (1), Julio Cesar R. LOPES (2), Simone C. N. ARAUJO (2), Walter PINHEIRO (2) 1 : AES Eletropaulo, Barueri, SP, Brazil, gustavo.silvestre@aes.com, sergio.caparroz@aes.com 2 : TAG Inovação Tecnológica, São Paulo, SP, Brazil, julio.lopes@tagpower.com.br, simone.araujo@tagpower.com.br, walter.pinheiro@tagpower.com.br The aim of this paper is to present the experience acquired and the results obtained during the execution of an R&D project development of equipment, with insulated cables and terminations, for temporary connection between sections of overhead subtransmission lines and substations of AES Eletropaulo that is the electricity distribution utility of Sao Paulo City, Brazil. In Brazil, the regulatory requirements that reflect the aspirations of the society regarding the continuity of electricity supply are increasing. Thus it is essential that the maintenance services, construction and expansion of the electrical system are executed by reducing outages, mainly due to scheduled services. Nowadays, one way used for this purpose when performing maintenance on overhead transmission lines towers is to build variants, employing in its implementation temporary structures and all the infrastructure (foundations, grounding, etc.) required. These variant constructions require time, space and loss of materials and services used therein. The lack of space in the right-of-way of transmission lines and substations of AES Eletropaulo creates considerable difficulties, even it is impossible, to implement these variants, which increases the time needed for scheduled outages and maneuvers as well as increases the risk of accidental shutdowns during construction or reconstruction of sections of lines and substations. Another not less important aspect is the amount of waste during the construction, which increases costs and enhances the environmental problems. Aiming to solve this problem AES Eletropaulo decided to invest in a research and development project that has as main objective the development of new equipment in Brazil to be used in variants of overhead subtransmission lines and substations. Currently there is not in the Brazilian market a device with 138kV insulated cables that can be used as variants in the reconstruction of overhead subtransmission lines. It is noteworthy that the major difficulties encountered in developing this type of equipment were related to: A. The constitution of the insulated cable, which should be more flexible than the cables used permanently in underground lines, and can be moved without damage to it. Stands out as the main hindrance the high level of short circuit required by the electrical system of AES Eletropaulo; B. Dry and easy connection terminations; C. Development of a reel to accommodate the cable and terminations, and a system for pulling and winding the cable that could be used in places with limited space as the available areas in the right-of-ways of the subtransmission lines and substations of AES Eletropaulo. D. Development of the procedure for installation taking into account the particularities of the transmission overhead lines of the AES Eletropaulo system and in particular that its lines are located in densely populated regions. In this paper the obtained results and the studies that were the basis for the development of the equipment to make temporary connections between sections of overhead subtransmission lines and feeding lines to substations of AES Eletropaulo will be presented. JICABLE15_0069.doc Thermal capability of the XLPE power cable jacket under fault conditions Chinh DANG (1), Saleman ALIBHAY (2), Jacques CÔTÉ (3) 1 - Hydro-Québec Technologie, 1800 boul. Lionel-Boulet, Varennes, Québec, CANADA, J3X 1S1, dang.chinh@ireq.ca 2 - Hydro-Québec Équipement, 800 boul. de Maisonneuve E., Montréal, Québec, CANADA, H2L 4M8, alibhay.saleman@hydro.qc.ca 3 - Hydro-Québec Distribution, 140 boul. Crémazie, Montréal, Québec, CANADA, H2P 1C3, cote.jacques3@hydro.qc.ca Under fault conditions, short circuit currents are circulating in the neutral of the power cable and raising temporally the neutral temperature to a very high level. The resulting impact on the cable jacket as well as the underlying polymeric layers can be detrimental with perforated jacket and neutral penetration into the insulation shield. This could lead to an eventual dielectric breakdown of the cable. The maximum acceptable neutral temperature depends on the cable construction and the physical characteristics of the jacket and shield materials. This report shows experimental and modeling results obtained on an extruded power cable with an extruded XLPE jacket encapsulating the neutral. JICABLE15_0070.doc Progress control in the context of the project management for the execution of a 320kV HVDC land cable project - DolWin 2 Sebastian EBERT (1), Mariana BECKER (1), Johann BORN (1) 1 - ABB Power Systems Grid, Mannheim, 68309 Germany, sebastian.c.ebert@de.abb.com, mariana.budag-becker@de.abb.com, johann.born@de.abb.com Progress control is an important management procedure for projects in the execution phase. It helps to clarify many aspects for management decisions in order to reduce or avoid extra costs and time. We have introduced a new progress control method to the installation of a 320kV HVDC land cable project, which belongs to DolWin 2 cluster connection scope. ABB was responsible for the turnkey management as a general contractor. The main part of the land cable project installation management was delivered starting in early April 2014 and consisted of approx. 81 km remaining cable route (type extruded DC 2400 mm2 Al - see Figure 1) divided into 103 single sections of approx. 800 meters length and 102 joint bays, respectively 204 joints (prefabricated one-piece type), where each fourth joint was used as earth point. In addition 27 sections were situated in bird protection areas and must be executed within two months in order to not exceed the project deadline at the end of August 2014. The paper describes the implementation of a progress control method in mainly two phases: planning phase and execution phase. The phases were specially developed to comprise all site activity representation systematical and reliable. Using this methodology it was possible to plan different time schedules, compare these with the actual execution and report in order to inform and reduce the reaction time between all project stakeholders, as shown in the Figure 2. Fig. 1: ABB HVDC cable 2400 mm² Al Fig. 2: S-Curve report of the land cable installation This procedure ensured to deliver the identification of delay causes and their quantification easier and faster, which permitted a more useful implementation of countermeasures even during the project execution. Consequently the project was after five months of intensive work completed successfully and commissioned with the required DC voltage test (according to CIGRE TB No. 219) and DC oversheath test (according to IEC 60229,5). As a result the project achieved a very fast land cable system installation completion. In this context the progress control methodology was shown to be essential for this project configuration and its result. JICABLE E15_0071.do ocx Accelerated Alumin num Co orrosion n upon n Waterr Ingres ss in Dama aged Lo ow Volta age Unde ergroun nd Powe er Cable es. Bart KRU UIZINGA (1)), Peter WOU UTERS (1), F Fred STEENNIS (2,1) 1 - Eindh hoven University of Technology, Eind dhoven, The Netherlands s, b.kruizingaa@tue.nl, p.a.a.f.wouters@ttue.nl 2 - DNV GL - Energyy, Arnhem, The Netherlan nds, fred.steennis@dnvg gl.com Low Volttage (LV) un nderground power p cabless generally have h a good reputation iin terms of customerc a slow but steady grow minutes--lost and ageing phenom mena. Howe ever, in the Netherlands N wth in the number of faults is observed. o Sin nce the incre easing penetrration of de-c central geneeration is add ding more pressure e and given n the high costs c involve ed with rep pairing faults s, condition monitoring is under investiga ation. Due to o the low volltage level, o often occurring damages s don’t necesssarily lead to a fault directly. Damaged cables c with exposed co onductors ma ay go undettected for ve very long tim me. Many cables n nowadays em mploy aluminum conducctors. Inspec ction after fa aults in thesse cables so ometimes show the e presence of o white powd der, indicatin ng corrosion. For corro osion to occcur, three ele ements are rrequired. A metal, m potential differencce and an electrolyte. When a cable is dam maged and water w can rea ach the cond ductor, these e elements aare all present. In this situation n, aluminum oxide is formed on the surface of the t aluminum m. Due to thhe voltage hydroxide h concentrrates at the surface of the conducto or, causing a dissolution of the oxidee layer. This s process allows co orrosion to continue c until the cross-se ection is suffficiently reduced for a fauult to occur. To studyy this processs, a test setu up was desig gned. A cable e sample with an artificiaal damage is placed in a tank filled with wa ater. The watter is heated d and pumpe ed out period dically to sp eed up the corrosion process and allow fo or oxygen to reach the da amage spot. The cable ends are sealled and the sample s is energize ed to nomina al voltage. Th he process i s recorded by b a camera, taking pictuures periodic cally, and current m measuremen nts are taken at the same e time. Differrent paths in current flow have been identified, dependin ng on cable damage and d type. Initial tests were conducted c ov ver up to threee weeks of time t for a single sa ample. An exxample is giv ven in figure 1. Several configuration c s are tested,, and the effe ect of the water co onductivity is studied. The e water cond ductivity used d is similar to o that of averrage ground water. Figure 4: Example E of a aluminum corrosion in a 6 mm hole. During the first dayss, the speed of the proce ess already shows to be e significant.. A 6 mm in diameter hole, drillled into the conductor, fills f up with a aluminum oxide within se everal days. A continuous release of hydrog gen gas bub bbles is observed. During g the testing period, p the density of oxidde seems to increase and flakkes of oxide are release ed into the w water. At a later stage, small holess releasing hydrogen h bubbles show that th he oxidation continues. Current leve els are generally in the oorder of several milliamperess, varying over time. Further characte erization of th he current is currently undder investiga ation. This worrk reveals the e often found d, but hardlyy understood process as it occurs undderground. Corrosion C under this mechanism exceeds the rate of re egular corrosion if no voltage is applieed. The actua al rate as a functio on of the da amage size and materia als applied are a currently y under invesstigation, inc cluding a comparisson to the be ehavior of co opper conducctors. JICABLE15_0072.doc Transient analysis of 3-core SL-type submarine cables with jacket around each core George ANDERS (1), George GEORGALLIS (2) 1. - Lodz University of Technology, Lodz, Poland, george.anders@bell.net 2. - Hellenic Cables, Athens, Greece, ggeorgal@cablel.vionet.gr The IEC Standards 60853-1 and -2 give the formulae for the calculation of the cable conductor temperature variations when a step load is applied at time t=0. The method used in the standard is based on a reduction of a multi-loop ladder network representing lump parameter thermal model of the cable to a two-loop circuit and then solving the resulting differential equations using a Laplace transform. This paper will address two issues related to calculation of the transient rating of 3-core submarine cables with lead sheath or concentric wire screen around each core. 1. The IEC Standard 60853-2 gives equations for the reduction of a multi-loop thermal network of an SL-type cable to its two-loop equivalent for the calculation of the partial transients for long and short durations and cyclic loading. The first task of this paper is to show that the equations given in the standards need to be modified as they are in error in some parts. 2. The second task is to introduce a new model for the most common construction of the 3-core submarine cables with polyethylene layer over each lead sheath (or concentric wires) and common armour (either single or double). The IEC Standard does not deal with such cables at all. 3. The final task will be to discuss the calculation of the current ratings of 3-core submarine cables with non-magnetic armour. The diagram below shows a typical SL-type submarine cable with a jacket around each core. JICABLE15_0072.doc The numerical values shown above will be used in an illustrative calculation of the cyclic loading for this cable. An example of the new model is shown below with an assumption of a long duration transient (insulation capacitance is split into two components rather than four). JICABLE15_0072.doc Subscripts i, s, j, f, b, a and sr correspond to insulation, sheath, jacket, filler, bedding, armour and serving, respectively. p, p ', p " and p ''' represent Van Wormer coefficients for insulation, jacket, bedding and serving, respectively. Detailed calculations of a cyclic rating factor for such a network will be shown in the paper. In addition, a comparison will be made with the calculations performed in North America and elsewhere, which apply the Neher-McGrath method for cyclic rating computations. The paper will show that the rating obtained with both approaches can be vastly different and a discussion will be offered on the reasons for this and possible remedies. JICABLE15_0073.doc Hydro-Québec Advancements with Infrared Imaging for the Maintenance of the Underground Medium Voltage Cable System Michel TRÉPANIER (1), Jacques CÔTÉ (2) Hydro-Québec, 800 140 boul. Crémazie, Montréal, Québec, CANADA, H2P 1C3, 1 - trepanier.michel@hydro.qc.ca 2 - cote.jacques3@hydro.qc.ca Hydro-Québec Distribution has over 11,000 km of 12kV and 25kV medium voltage underground cables. The system is almost entirely composed of duct-installed bare concentric neutral cable, with 28kV XLPE or TR-XLPE insulation. Around 380,000 joints of different type, all rated 25kV are installed in 32,000 manholes. Considering the need to perform effective maintenance and to reduce the risk for workers of defective joints, a thermal imaging maintenance program has been in continuous development since 2000 at Hydro-Québec. Thermal Infrared Imaging was introduced in the IEEE 400 - 2012 Guide for Field Testing and Evaluation of the Insulation of Shielded Power Cable Systems Rated 5kV and Above. It is one of the most powerful diagnostic techniques of accessible medium voltage underground cable accessories installed on long or complex cable systems. Hydro-Québec is a leader in this field. The presentation will focus on the recent development of new inspection criteria to determine the thermal profile and behaviour of cable accessories based on experimental results. These new criteria simplify the analysis and allow the use of new, easier and lighter portable equipment. This new equipment will also be presented. Combined with the new criteria, this equipment requires less knowledge from the operator facilitating training. Inspection of manholes is therefore accelerated and less costly. This paper is a follow-up of the Jicable 2011 paper #0146 “Hydro-Quebec Experience with Infrared Imaging for the Maintenance of the Underground Medium Voltage cable System”. JICABLE15_0074.doc A NEW APPROACH FOR ESTIMATION OF THE DYNAMIC THERMAL RATING MODEL PARAMETERS Alireza FARAHANI (1) George J. ANDERS (2), Wouleye KAMARA (1), Emmanuel BIC (3), Uwe KEPPLER (4) 1-CYME Int. - EATON Corp., Montreal, Canada, alireza.farahani@eaton.com, Wouleye.kamara@eaton.com 2-Lodz University of Technology, Lodz, Poland, george.anders@bell.net 3-General Cable, Montreau, France, EBic@generalcable-fr.com 4-AP Sensing, Boeblingen, Germany, uwe.keppler@apsensing.com Distributed Temperature Sensing is a well-established technology that provides in real time the accurate temperature distribution all along the cable route for cable systems equipped with a fibre optic wire. While the temperature profile can be used to locate the hot spots within a power cable installation, the main interest is to optimize the usage of these assets. Generally, transmission operators install dynamic rating systems to improve the current rating of the circuit. There are two main scenarios for which the current rating increase can be used. 1. Time limited current rating increase: a dynamic rating system that gives a temporary rating increase to the circuit can be used by the transmission operator to schedule outages and generators in a more efficient manner. 2. Long term current rating increases: a dynamic rating system that gives a permanent rating increase allows the transmission operator to avoid the need for transmission circuit upgrades or for new circuits. In order to obtain reliable results, two most important parameters in rating calculations have to be estimated from the measured fibre optic temperature at a hot spot point and cable current. These are the soil thermal resistivity and soil ambient temperature. The ambient temperature is sometimes measured but, in the vast majority of practical installations, it is not known. Both parameters change in space and time and since the variations of these parameters are not known, normally a conservative approach that assumes the worst case scenario is used. The idea of the dynamic rating model discussed in this paper is to estimate the unknown time varying input parameters to match the DTS readings at a given point. The point which is monitored could be inside a spare duct close to the cables or in a direct contact with the cable surface or inside a steel tube inserted in the layer containing the wire screen. This paper introduces a mathematical optimization method to estimate the soil thermal resistivity soil and ambient temperature amb from the measured value measured as they change during the time interval jt; j 1,..., N with N t the total time interval (usually 24h). The optimization problem can be formulated as follows: min j t , 1 N j 1 est soil 2 , amb measured j t t where est is the computed value of the temperature at the measurement point. The paper discusses the solution to this problem and shows that it works remarkably well in several practical installations. In particular, it discusses the test results obtained using the readings of a DTS system installed by AP-Sensing at the SILEC CABLE test facilities (see figures below). The test setup provided the possibility to compare calculated RTTR conductor temperatures with actual measured values in a voltage free reference cable. The test setup involved various thermal sections: sand (directly buried), protective tubing in sand and an unventilated utility tunnel. More than 300m of HV cable were deployed in an outdoor test field, which made the test setup similar to a real JICABLE15_0074.doc installation with the uncertainties in geometry, soil thermal properties variations due to wheather changes in the course of an entire calendar year. Fig. 1 Fig. 2 JICABLE15_0075.doc CURRENT RATING OF POWER CABLES WITH TEMPERATURE LIMIT IMPOSED ON BACKFILL/DUCT BANK BOUNDARY Alireza FARAHANI (1), George J. ANDERS (2), Laure GAROUX (1), Wouleye KAMARA (1), 1-CYME Int. - EATON Corp., Montreal, Canada, alireza.farahani@eaton.com, Wouleye.kamara@eaton.com, laure.garoux@eaton.com 2-Lodz University of Technology, Lodz, Poland, george.anders@bell.net Core temperature has been typically the limiting parameter for rating insulated cables installed underground. There are, however, recent interests to rate underground cables based on the temperature at the most external boundary in direct contact with the native soil. This could be the cable jacket, duct or pipe for directly buried circuits and backfill/duct bank boundary for duct banks or backfill installations. The purpose is to limit the temperature of this boundary below the critical value above which moisture migration and consequently soil dry out could happen. Calculation of the cable component temperature can be easily handled with the lump parameter equivalent of a cable thermal circuit. However, obtaining the backfill/duct bank boundary temperature is not a trivial task, especially when there are several circuits of different types in one installation including many duct banks and backfills. Actually, since there is only one point on the backfill/duct bank boundary with the highest temperature, the number of unknown currents is higher than the number of available equations. The temperature at different points on the backfill or duct bank boundary can be significantly different and the hottest point could change position when different current distributions are considered. This is in contrast with direct buried installations where one can assume all points on the duct, pipe or cable’s surface are approximately at the same temperature. In addition to obtaining the currents that avoid soil dry out, we are also interested in maximizing the total ampacity of the installation. Hence, for a given target temperature imposed on the most external boundaries of a cable installation in contact with the native soil, the unknowns are the currents through each circuit. This paper presents a new method for cable rating calculations when the temperature limit is imposed on the duct bank/backfill boundary or the most external cable layer for direct buried installations. The method uses a combination of a numerical and analytical solution and is described in detail in the paper. Several approaches can be envisaged to handle this problem. Three are described in the paper. One of them is an iterative procedure where the current I (k) for cable k found at the previous step has been changed by the value of I (k ) to meet the required temperature change (k ) at the point M on the backfill boundary in order to reach the desired value. The equation developed in this work to affect this change is shown below, with the same notation as in the IEC Standard. I k k k 1 k k R k I k log d d eq 1 2 kM kM Key part of the proposed method is to find the location of the point M with the highest temperature on the backfill boundary and take into account the multiple heating sources. The employed procedure is described in the paper. Figure below shows the results of the analysis for a system composed of cables located in a duct bank (lower installation with 2 circuits) and a single circuit in a backfill above the duct bank. The temperature limit of 50°C is imposed on the backfill/duct bank boundaries. We can observe that the highest conductor temperature is, in this case, below 60°C. JICABLE15_0075.doc Fig.1 Cable rating with backfill boundary limited to 50°C Another example involves two different circuits and a heat source and the cable surface temperature is limited to 50°C. Fig. 2 Cable rating with outer surface of the pipe type cable and jackets of the direct buried cables limited to 50°C JICABLE15_0076.docx Latest technologies for submarine cable protection and repair Mamoru HASEGAWA (1), Satoshi TOMIOKA (1) 1 : Sumitomo Electric Industries, Ltd., 5-5-23,Torishima,Konohana-ku,Osaka ,554-0051 JPN, Mamoru-hasegawa@sei.co.jp, Satoshi-tomioka@sei.co.jp Cable protection and repair are the long-time most focused issues, especially for improving the reliability of the submarine cable transmission line. Recently, we have successfully repaired a long distance submarine cable of approx. 45 km at 200 m deep in Japan. Design of submarine cable protection is one of the most essential engineering to construct a highly reliable submarine cable circuit against sea traffic and active trawler fishery. However, a total solution is required upon study of not only the cable protection, but also economical construction cost, environment, safety aspects, maintenance, repairing method and so on. This paper generally introduces the latest technologies for submarine cable protection including high accuracy protection in deep water and repairing technologies based on our field experience. Generally, it is not realistic to apply numerous divers for the cable protection work at the area of deeper than 30 m deep as well as for the long-distance cables. Cable burying with suitable burying machine, rock dumping, cable laying with polyurethane protection pipes are applied conventionally, based on the site conditions, seabed conditions, construction cost budget, clients requirement and so on. In case the seabed sediment allows applying a burying machine, water jet simultaneous burying and/or post-burying shall be one of the solution for the cable protection. Most appropriate proposals of protection shall be finalized as a study of the total solutions, in consideration of location, environment, safety aspects and cost effectiveness. In particular, rock dumping cost for the long-distance cable is normally very high, therefore, we have developed a cost effective cast iron cover protected laying method, instead of rock dumping and also polyurethane protection pipes. A pinpoint cable protection is required at deep water, such as 300 m deep, as well as existing cable crossing. Installing concrete mattresses or filter unit filled with gravel and rocks is basic method of the pinpoint protection, however, especially at the deep water, high accuracy of the operation shall be required to minimize the construction cost. This paper introduces our own high accuracy protection method especially for deep water. If the submarine cable was laid on undulated seabed, the cable free span shall be unavoidable. In order to prevent metal sheath fatigue due to Vortex Induced Vibration at strong current, cable protections to reduce the free span length are required normally. Recently, newly developed cable protective tube with fins has been introduced, attaching with assistance of Remotely Operated Vehicle (ROV), it will prevent the Vortex Induced Vibration. The Cable laying technique to reduce the free span length is progressing year by year, and we also have developed our own unique cable tension control system to reduce the cable free span length during cable laying operation. Cable repairing method is also developed in-house to reduce the cable repair lengths, repair work duration for considering the impact of the repairing costs and the environment, based on our recent cable repair work for approx. 45 km, at 200 m deep in Japan. JICABLE15_0077.docx Developement of the Super-capacity insulated wire cable for distribution line. Kyongtae Lee (1), Jinwoo Kim(1), Youngjun Kim(1), Moonseok Lee(2), Mincheol Lee(3), Sangwon Park(3), Seyoung Park(3), Seunghee Lee(3) 1 - ILJIN Electric, Hwasung-si, Korea, kyongtae.lee@iljin.co.kr 2 - SK chemical, Daejeon-si, Korea, lms7055@hanmail.net 3 - KEPCO, Kwang-ju, Korea, lee4444@kepco.co.kr As development of industrial society continues to increase, the metropolis becomes to need more electric power. To meet recent increasing demands for electric power in metropolis, we should expand a distribution line. But it can be expensive to charge the cost of expansion work. It also doesn't make a good appearance when the distribution cable is installed in the metropolis. Therefore, we are considering solving this problem in two aspects as below. A First thing is to enlarge “size of conductor” or reduce loss of “ac resistance” for conductor as using enamel coating. However, it causes to gain the weight and complex process of production for cable. So, it does not seem to be efficient because the cost of making cable is increased and it could lead to other problem for the cable. Another thing is to raise the operating temperature of cable due to using the thermal-resistant compound. If electric current is passed through the electric power cable, it is created heat by resistance. Temperature of cable steadily rises as increasing load current. XLPE has been widely used to insulate the CV cable because its high thermal stability might be originated from cross-linking structure. However, it has restriction on the operating temperature up to 90 . The insulation has properties that rapidly fall if it is continuing above 110 for a long time, Therefore, it can transmit more current if thermo-stability of insulation is elevated in the cable of the same structure. In this paper, we deal with developing insulated outdoor cable that can increase in normal operating condition of distribution cable from 90 to above 120 and producing, verifying for high-capacity cable Development of insulation increased in normal operating temperature through special cross-linker is added special PE. It is weighed new XLPE cable against existing XLPE cable and compared with same structure. In addition , we verified aging property throughout long-term experimental test. JICABLE15_0078.docx Space charge distribution in XLPE plates with non-uniform conductivity Carl-Olof OLSSON (1), Birgitta KÄLLSTRAND (1), Maria LUNDMARK (1), Kenneth JOHANSSON (1), Sara ARNSTEN (1), Bin MA (1), Markus SALTZER (2), Marc JEROENSE (2) 1 - ABB AB, Corporate Research, Västerås, Sweden, carl-olof.olsson@se.abb.com, birgitta.kallstrand@se.abb.com, maria.lundmark@se.abb.com, kenneth.johansson@se.abb.com, bin.ma@se.abb.com 2 - ABB AB, High Voltage Cables, Karlskrona, Sweden, markus.saltzer@se.abb.com, marc.jeroense@se.abb.com The PEA method has been used to measure the distribution of space charge in XLPE plates having non-uniform as well as uniform distribution of conductivity. Based on the one-dimensional space charge distribution, the electric field distribution and conductivity distribution are evaluated. XLPE plates have been prepared to have either uniform or non-uniform conductivity. Since the conductivity of these samples is dominated by the concentration of by-products from dicumylperoxide, different conductivity distributions can be prepared by partly degassing the plates. Uniform plates have been kept in diffusion tight wrappings before the PEA measurement, and diffusion has also been minimized during the measurement. Non-uniform plates have been made by degassing from one side of the plates. For 2 mm thick plates, a concentration gradient that spans the entire thickness is obtained after 3 h at 80°C keeping one side of the plate free for the air and the other side blocked by a tight metal foil. The concentration distributions have been calculated using a numerical model, and experimental verification using a microtome and GC-FID analysis has been made. Simulations of the electric field and space charge distributions as function of time have been compared to the experiments, and good agreement has been obtained. Depending of the conductivity, the total measurement times are adapted to allow for the transition from capacitive to steady-state resistive distribution of the electric field. When the dielectric time constant is long, it is inevitable that some diffusion of by-products will also influence the measured distribution of space charge. This as well as other challenges related to PEA measurements on XLPE insulation will be discussed. JICABLE15_0079.doc Robust characterization of the DC-conductivity of HVDC insulation materials at high electric fields Hossein GHORBANI (1), Carl-Olof OLSSON (2), Carl-Johan ANDERSSON (3), Villgot ENGLUND (3) 1 - ABB AB, High Voltage Cables, Karlskrona, Sweden, hossein.ghorbani@se.abb.com 2 - ABB AB, Corporate Research, Västerås, Sweden, carl-olof.olsson@se.abb.com 3 - Borealis AB, Stenungsund, Sweden, CarlJohan.andersson@borealisgroup.com, villgot.englund@borealisgroup.com Testing techniques should be easy to implement, give meaningful and robust results with a high reproducibility that makes it easy to analyze and compare results. When developing and comparing different materials for use as electrical insulation for DC applications, the use of relevant small scale test equipment and methods are of most importance. DC-conductivity, measured at high electric fields with controlled thermal conditions, is an important and critical measurement when investigating different insulation materials. The thickness of the samples might need to be increased when the conductivity is measured on materials containing substances that can diffuse out of the sample. At the same time the electric field should be at the same level as can be foreseen for cable applications. With the equipment used in the present study, reliable measurements can be made up to 50kV on samples having 1 mm thickness. In this paper we present a comparison between measurements performed on plaques at three different test facilities. The test setups consist of a three-terminal cell made of brass with identical dimensions and with similar test procedure. All measurements were done on non-degassed samples and effort has been made to reduce the leakage of peroxide byproducts during the testing cycle. Concentrations of peroxide decomposition products were measured before and after the tests in order to estimate the amount that was diffused from the samples during testing. The results show that by careful sample preparation and having right test procedures and equipment, it is possible to achieve robust measurement results with a high reproducibility. JICABLE15_0080.doc Study on overvoltage of 500kV cable-overhead mixed lines. Biao YAN (1), Li ZHOU (1), Jie CHEN (1), Fengbo TAO (1), Jingjun WANG (1) 1 - Jiangsu Electric Power Company Research Institute, Nanjing, China, fengchuiguolai@126.com, zl_jtt@163.com, 2008840320@163.com, hvtaofb@163.com, 15105168881@163.com In many industrial and national standards about extra-high voltage power transmission lines, guidelines of overvoltage and insulation coordination are based on the results of studies on overvoltage of overhead lines. Compared with the overhead line, the power cable has a larger capacitance to ground, which affects the level of over-voltage transmitted by the power cable. A hybrid power transmission line project was selected in this paper, combined with the availability of reactive power compensation for transmission line, simulation of overvoltage on 500kV hybrid power transmission line under typical running and operating conditions are processed, including power frequency overvoltage and switching overvoltage, results of these computations provide references for power engineering design. JICABLE15_0081.doc Localized Temperature Sensing (LTS) as new approach to HV cable system monitoring and uprating Xabier BALZA (1), Javier BENGOECHEA (2), Alberto GONZÁLEZ (3), Ángel MARTÍN-DORADO (4) 1 - General Cable, Barcelona, SPAIN, xbalza@generalcable.e 2 - Lumiker, Bilbao, SPAIN, javier.bengoechea@lumiker.com 3 - UFD, Madrid, SPAIN, agonzalezsan@gasnatural.com 4 - UFD, Madrid, SPAIN, amartindo@gasnatural.com Even if distributed temperature sensing (DTS) has been accepted as the best way to manage undergrounded HV cable systems’ exploitation, there are several inconveniences that have stopped its general usage and with it the installation of fiber optics in cable screens. The concept of Localized Temperature Sensing (LTS) tries to give an answer to utilities’ needs of monitoring the real operation temperature of certain existing lines, in order to be able to optimize their exploitation regimes even if there is no fiber optics inside cable screens. While DTS systems use Raman or Brillouin effects, LTS system uses Bragg effect to measure the temperature in some defined points of the cable system with measurement answers every second and accuracies of 1 ºC. These Bragg sensors can be connected in parallel through standard G652 single mode fiber optics, so they are installed in the accessible points of the cable route (joint bays, substations, GIS building) without the necessity of laying new fiber optics in case there are available communication fiber optics in parallel to the HV circuit. Each sensor is customized according to the final place where it will be installed in order to measure temperature, strain or both, and to fulfill the IP and pollution requirements. This article presents the pilot installation of the first LTS system applied to a cable system, hosted by UNION FENOSA DISTRIBUCIÓN in one of their HV circuits in Madrid. It describes the development of the equipment, its specifications, the process of customizing the sensors, their installation and the first results of the on line measurements. LTS will make possible the on line temperature measurements required to achieve the exploitation flexibility necessary to answer to the challenges that the HV grid will face in the forthcoming years with a reduced installation and economic impact. JICABLE15_0082.docx Testing submarine cables for combined axial compression and bending loads Andreas TYRBERG (1), Erik ERIKSSON (1), Jørgen GRØNSUND (2), Frank KLÆBO (2) 1 -ABB AB, High Voltage Cables, Karlskrona, Sweden, andreas.tyrberg @se.abb.com, erik.x.eriksson@se.abb.com 2 - MARINTEK, Department of Structural Engineering, Trondheim, Norway, jorgen.gronsund@marintek.sintef.no, frank.klaebo@marintek.sintef.no Dynamic analyses are performed to verify that the structural integrity of a submarine power cable is maintained during an installation campaign. The analysis can be performed for different weather conditions with the purpose to establish the weather restriction of an installation operation. For dynamic cables, a dynamic global analysis is performed to establish the extreme and fatigue loads that will be applied to the cable during its service life. Since the dynamic cable is a permanent installation it is important to verify that the integrity of the cable is maintained even during the worst storm conditions. In the analysis, the curvature, torsion and tension of the cable is evaluated and the results are compared to the cable integrity criteria. In the case of large vertical movements of the vessel or host platform, the cable can be subjected to axial compression, i.e. negative tension. There are currently no standards or recommendations which give guidance with regards to acceptable levels of axial compression in power cables, nor how to verify that the cable can sustain axial compression. Due to lacking knowledge, common industry practice is therefore to not allow axial compression. For cable laying “zero compression” will often be the limiting criteria, thereby restricting the weather window of the installation operation. For a dynamic installation a zero compression integrity criteria can have a large impact on the feasibility of the configuration. Excessive axial compression can result in birdcaging or buckling of the helical elements in the cable. The combination of compression and bending is assumed to reduce the compressive capacity of the cable. Testing on flexible pipes, with helical tensile wires, has shown that compression and cyclic bending, can trigger lateral buckling of the armour wires. To verify that a power cable can sustain combined compression and cyclic bending loads, a test program has been performed in a new built full-scale rig specially designed for testing combined compression and bending loads. The loads used in the test program where established based on the extreme loads from the dynamic analysis. This paper describes the new rig and the test program performed. The paper also gives background to the loads used in the test program and discusses the potential failure modes associated with axial compression. JICABLE15_0083.docx Assessment of Overheating in XLPE MV Cable Joints by Partial Discharge Measurements Espen EBERG (1), Kristina I. BERGSET (2), Sverre HVIDSTEN (1) 1 - SINTEF Energy Research, Sem Sælands veg 11, NO-7465 Trondheim, Norway, espen.eberg@sintef.no, sverre.hvidsten@sintef.no 2 - The Norwegian University of Science and Technology (NTNU), Department of Electric Power Engineering, NO-7465 Trondheim, Norway, kristina.bergset@gmail.com There are 140.000 km of cables in the Norwegian distribution grid, with more than 40% installed during the 1980s and 1990s. A significant number of these cables have reached their expected lifetime of 30 years. Further, there are likely more than 100.000 splices installed in the Norwegian distribution grid. One major challenge related to service reliability of these cable links, is overheating in XLPE joints. The overheating is caused by bad metallic connections in the joint. Such connections are located to e.g. the metallic conductors and joint ferrule, the ground screens of the cable and joint or the cable ground screens and the outer aluminum water tight laminate. In this work partial discharge (PD) measurements have been performed on service aged 24kV XLPE joints. The joints have been removed from service after only some years due to joint failures in the same cable link. The statistical distribution of the PD activity was measured at voltages up to 12kV at very low frequency (VLF, 0.1 Hz) and at power frequency (50 Hz). This was done in order to examine if PD occurred at service stress and the possibility to detect the discharges by using a VLF diagnostic test method. The results show that the PD inception voltage (PDIV) was decreased for an increasing test voltage frequency. At 0.1 Hz the PDIV was found to be above service voltage, whereas it was below service voltage for 50 Hz. This implicates that PD activity is likely present at service voltage, but this is not assessed by the PD measurements at VLF. Dissection of the joints reveals that a high contact resistance between the ground screens of the cable and joint has caused overheating with subsequent damage to the insulation system in the joint during service. JICABLE15_0084.docx Potential Use of New Water Tree Retardant Insulation in Submarine Cables. Stephen CREE (1), Paul CARONIA (2), Timothy PERSON (3) 1 : Dow Electrical & Telecommunications, Bachtobelstrasse 3, Horgen, Switzerland, CH 8810. cree@dow.com 2 : Dow Electrical & Telecommunications, 400 Arcola Rd., Collegeville, Pennsylvania, PA 19426, USA. caronipj@dow.com 3 : Dow Electrical & Telecommunications, 400 Arcola Rd., Collegeville, Pennsylvania, PA 19426, USA. persontj@dow.com As the renewable energy industry considers larger wind turbine spans and larger arrays with more turbines per array, the issue of the need for higher voltage array cables that have low electrical energy losses is brought into consideration. For example a move from 33kV to 66kV array cables is leading to the evaluation of ethylene-propylene rubber (EPR) insulated cable cores. However they may not be the only option for a robust tree retardant submarine cable insulation at this voltage level. This paper looks at the option of using additive water tree retardant crosslinked polyethylene as the insulation material of choice for submarine cable cores up to 69kV. In addition to an insulation having good resistance to the growth of water trees, the insulation should also maintain a high dielectric strength while in a wet environment and a low loss factor. As part of this evaluation we present data on the performance of the new medium voltage cable insulation DOW ENDURANCE™ HFDC-4202 EC. This compound exhibits superior retention of breakdown strength following wet aging testing, both to ICEA and CENELEC protocols. This paper also shows that unlike other insulation systems, such as water tree retardant copolymer and clay filled EP, additive water tree retardant 4202 shows a limited increase in dissipation factor as temperature and stress level is increased. In addition as shown in Figure 1, unlike copolymer water tree retardant cable insulation systems, additive water tree retardant insulation systems maintain a relatively low dissipation factor following wet aging under electrical stress. Water tree retardant “4202” has also demonstrated excellent performance when operated with high conductor temperatures in both dry and wet environments. As shown in Figure 2, when operated at a 105°C conductor temperature in a dry environment, “4202” has a stable and low dissipation factor across a broad temperature range. As shown in Figure 3, at electrical stresses up to 7kV/mm, “4202” TR-XLPE has a loss factor that meets the requirements for a homopolymer XLPE insulated cable. At higher electrical stresses, the dissipation factor of the “4202” TR-XPLE increases due to the influence of the water tree retardant technology. This demonstrates that for cables operated up to 7kV/mm stress (or about 138kV), “4202” TR-XLPE is an excellent insulation for enhancing a cable design’s capability to meet the cable users expectations for a long life cable system while providing an insulation that is robust to resisting the impact of water on the cable that may be encountered if the cable metallic barrier is damaged. As shown in Figures 4 and 5, after being operated in a wet environment with a 105°C conductor temperature for 1095 days, the “4202” TR-XLPE insulation maintains a high dielectric strength and lower dissipation factor than clay filled EP insulations. The “4202” water tree retardant insulation meets the ICEA requirements for a class III 105°C insulation. In summary the data in this presentation proposes that submarine cable makers and utilities consider the use of an additive water tree retardant polyethylene as insulation for higher voltage submarine wind farm array cables. JICABLE E15_0084.do ocx Figure 1:: Cable Insullation Dissipa ation Factor a as a Function n of Insulation n Type and W Wet Aging Tim me. Dissipation Factor (%) 0.500 0.400 25C 0.300 105C 140C 0.200 0.100 0.000 0 1 2 3 4 A Aging Time (weeks) 5 6 Figure 2:: “4202” TR-X XLPE Cable Ageing; A Dissi pation Factor versus Tem mperature. Figure 3:: Cable Dissip pation Factorr at 100°C as a Function of o Electrical Stress S Level 1600 64 1400 56 1200 48 TR-XLPE 1000 40 800 32 EPR 600 24 400 16 200 8 0 200 400 600 800 Days) Aging time (D 1000 1200 Figure 4:: Dielectric Sttrength as a Function of A Aging Time and a Insulation n Type while Aging in Wa ater with a Conductor Temperatu ure of 105°C. dissipation factor (%) JICABLE15_0084.docx 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 TRXLPE Initial TRXLPE Aged EPR Initial EPR Aged Figure 5: Cable Dissipation Factor Following 1095 Days Ageing in Water JICABLE15_0085.docx Urban 220kV Cable Transmission: Perpetual Developments Arvind Kumar Sharma, Vikas Sonar, Sanjeev Bagde, Vikrant Patil 1 - Reliance Infra Ltd., Mumbai, India, arvind.kumar.sharma@relianceada.com, vikas.sonar@relianceada.com, sanjeev.bagde@relianceada.com, vikrant.patil@relianceada.com Reliance Infrastructure-Mumbai Transmission (RInfra-MT) is a consistently growing business arm of Reliance Infrastructure Limited providing bunch of power transmission and transmission related services to Mumbai consumers which pools, owns and operates a part of the intrastate transmission system of Mumbai in Maharashtra having a line specific license issued by Maharashtra state Regulatory Commission (MERC) for a period of 25 years. Preamble: Improved standard of living in developing countries resulted into rapid developments in commercial sectors & huge infrastructures projects leading to increased per capita consumption of power. Thus, harmonizing the power needs has now become a massive challenge in front of Power utilities. Steadfast power transmission is the need of urban infrastructure for meeting power requirements. EHV Cable network is the only viable solution for power transmission network in congested developing cities due to environmental issues and non-availability of adequate ROW (Right of Way). Upholding highest degree of quality of cable structure is an essential owing to reliability obligations, huge cost involvements in projects and long life expectancies. However, installation of EHV cable in predominate congested corridor pose challenges owing to other peripheral concerns. RInfra-MT realized incremental improvements in cable installation practices over the time reflected into innovative designs & concepts of trenching and joint chamber construction. The paper covers the revolution in 220kV underground cable trenching methodologies which RInfraMT have adopted during various projects within Mumbai city and institutionalized threading of EHV cable through concrete encased HDPE duct bank & joint chamber through which the second circuit is also protected mitigating snaking. Objective: Development of cost effective techniques for enhancing life cycle of 220kV EHV cable network. Collaborate in establishing high standard practices of underground EHV cable installations in achieving Zero cable sheath faults & maximizing ampacity. Methodology: The paper touches transition from cable laying in open trench, however focuses on EHV cable threading through concrete encased HDPE pipes laid under plethora of utilities mitigating challenges of low water table, traffic etc. and achieving damage free cable sheath. Further, the project is implemented without any damage to other utilities adhering safety, quality & OHSAS requirements. Evolution in design of joint chamber construction keeping other circuit in HDPE pipes which guards EHV cables from damages inside joint chambers and facilitates safe working place during maintenance. Conclusion: Incremental improvements in design and concepts of 220kV cable trenching & joint chamber construction proved their ability to maintain quality of cable system even though in unorganized underground utility structures and slender underground corridor. Our experience in this area can be used effectively by other utilities in overcoming underground transmission engineering and construction issues successfully. JICABLE15_0085.docx This paper will act as a guide for helping power engineers to build underground Transmission network in crammed cities of developing countries. JICABLE15_0086.doc Thermal Ratings of Submarine HV Cables Informed by Environmental Considerations Timothy HUGHES (1), Timothy HENSTOCK (1), James PILGRIM (1), Justin DIX (1), Thomas GERNON (1), Charlotte THOMPSON (1) 1 - University of Southampton, Southampton, UK, t.hughes@noc.soton.ac.uk, then@noc.soton.ac.uk, jp2@ecs.soton.ac.uk, J.K.Dix@soton.ac.uk, Thomas.Gernon@noc.soton.ac.uk, celt1@noc.soton.ac.uk With recent investments in projects like offshore power generation and international megagrid initiatives, submarine HV cables are becoming increasingly essential for modern power transmission strategies. Understanding the thermal conditions that these cables are likely to be exposed to is vital to ensure that they are efficiently and economically deployed. A lot of research has been carried out on the thermal behaviour of land-based cables. However the performance of submarine cables has not been extensively investigated despite numerous key differences between the two respective environments. For example, the marine environment can vary on a much more dynamic time scale. Migration of sedimentary bedforms may cause variations in the height of the seabed (i.e. cable burial depth) of up to 5m per year. We have developed 2D finite element method (FEM) simulations to assess the impact that certain environmental parameters (sediment permeability, thermal conductivity, and cable burial depth) have on the thermal performance of a cable buried in the marine environment. Both conductive and convective processes are accounted for within the porous burial sediment, and a conductive model is incorporated for the constituent components of the cable. Traditional techniques for calculating current ratings for terrestrial cables (e.g IEC 60287) commonly assume that the transfer of heat within the burial medium is dominated by conduction (convection is often neglected, or treated in an oversimplified manner). For low sediment permeabilities, fluid flow is restricted, and heat is dissipated almost exclusively by conduction from the surface of the cable into the environment. The thermal conductivity of the surrounding sediment and the cable burial depth strongly influence the efficiency of heat transfer away from the cable; behaviour that echoes the predictions of existing methods. However, the model suggests that for sediments with a high permeability, a significant amount of heat is transferred by convection (in fact for some sediments, convection is likely to be the dominant mode of heat transfer). In circumstances where this convection is significant, the additional cooling effect can drastically reduce the temperature of the cable for a given current load. Another consequence of significant convective heat transfer is that the influence of the thermal conductivity and burial depth parameters on the cable temperature is diminished. Augmenting cable current rating calculations to account for convective heat transfer from submarine HV cables may result in a higher current carrying capacity, or a reduction in the required amount of conductor material. Understanding how the various environmental controls affect the efficiency of heat transport in marine sediments is therefore crucial to help determine which types of sediment will provide a beneficial thermal environment for submarine HV cables. JICABLE15_0087.docx Results and verifications from REE experience on monitoring isolated cables with DTS Gabriel Alvarez-Cordero (1), Lourdes Soto-Cano (1), Gerardo Gónzalez-Morales (1) 1 - Red Eléctrica de España (REE), Alcobendas (Madrid), Spain, galvarez@ree.es, lourdes.soto@ree.es , ggonzalez@ree.es The ampacity of isolated cable, for the transmission grid or for the distribution grid, is conditioned by the maximum temperature that its insulator could withstand (without compromising its life span). This temperature is related to the maximum current that the circuit could transmit. Red Eléctrica de España (Spanish Transmission System Operator) calculates the ampacity (current-carrying capacity of cables) under the hypothesis of steady state (Std. IEC 60287), as well as standard ground and environmental conditions. The Power Control Centre operates the isolated cables in such a way that their ampacity is not exceeded taking the appropriate measures for this purpose. The load regime of all transmission circuits, shows daily peaks, off - peaks and transitions between them, unique for each day, being far from constant or having a repetitive cyclic regime. On the other hand, changes in the load regimen are not reflected instantaneously in the temperature of the isolated cable due basically to the heat storage capacity of the surrounding ground, and also the isolated cable, resulting in the concept of thermal inertia. All this leads to the inference that the ampacity, under the hypothesis of steady state, may exceed the currently value, without reaching or exceeding the maximum isolated cable temperature, thus resulting in a more flexible and optimized system operation. To verify this idea, REE has been monitoring real-time temperature in 220kV, 132kV and 66kV isolated cables with DTS technology (Distributed Temperature Sensing) since 2012, in the scope of different R&D projects. The DTS technology that is being used is based on Raman effect and all the results are fully satisfactory. The distributed measure of temperature is taken in the sheath of the isolated cable, fiber optic cable with a stainless steel or plastic sheath was placed. This gives more accuracy in the calculation of conductor temperature than the usual installation of external optical fiber. The analyzed facilities include: shallow buried sections (in concrete ductbank), deeply buried sections (casing pipes) and, in the coming months, submarines sections (interconnection between islands) and aerial sections (ascend to towers). Some of the objectives of this experience consist in the verification and quantification of thermal inertia, as well as quantification of maximum temperature peaks and their correlation with load regime and other parameters. Furthermore, thermodynamic models used in the simulations have been verified with FEM simulations based on the real data from DTS and current measurements. These solid arguments can be applied to the development of new flexible and optimal procedures for the efficient and safe operation of isolated cable circuits under a more realistic approach to ampacity. JICABLE15_0088.doc Choice of electrically conductive plate for shielding the magnetic field from underground high voltage cables Dr. Guoyan Sun (1), Jens Riesinger (1), Oldrich Sekula (1), Dr. Pietro Corsaro (1) 1 - Brugg Kabel AG, Switzerland, guoyan.sun@brugg.com, jens.riesinger@brugg.com, oldrich.sekula@brugg.com, pietro.corsaro@brugg.com This paper reports the design and simulation of electromagnetic shielding for a 275kV power system to be installed in Austria with a requested limit of magnetic field to public area of max 100 µT. The allocations and current rating of high voltage cables are predefined. Finite Element Method (FEM) is used for the calculation of the magnetic field. The preliminary results show the exposure limit can be kept in some situations by arranging the current phases in a right way without any shielding. For other cases magnetic shielding has however to be applied. Plates are the best choice for installation in respect of space limitation of allocations. Further FEM simulations are executed for selection the material and size of the plates. It has been found out that using plate made of nonlinear magnetic material the magnetic field is much enhanced at the borders of the plate and the ohmic loss in it is even bigger than the loss in cable conductor. Conductive plates have shown a better shielding effect and the energy losses in them are considerably lower. From the technical point of view copper is best suited but it would result in an expensive solution. As a final result Aluminum is selected as the plate material. When transforming the analytical solution into a practical installation additional challenges have to be overcome. The problem of Al oxidation and galvanic corrosion should be taken into consideration, installation accessories made of non-magnetic material have to be used to avoid local enhancement of magnetic field, etc. Shielding plate An example of allocation of high voltage cables and the corresponding FEM calculation results JICABLE15_0089.doc Refinement in ambient temperature selection for current rating calculations Frédéric LESUR, Victor LEJOUR RTE, Paris, France, frederic.lesur@rte-france, victor-antonin.lejour@rte-france.com, The ambient temperature (the temperature of the surrounding medium - air or soil - under normal conditions), is one of the most influent parameters for the calculation of the maximum permissible current rating of cables. The IEC 60287-3 standard gives reference ambient temperatures and thermal resistivities of soil in various countries. For example, 10°C and 20°C are recommended values for France respectively in winter and summer. A study was performed ten years ago in order to draw a French map with more accurate input data for the cable system designer. Areas were outlined with three levels of ambient temperatures (cold, intermediate, warm). A new study was recently launched from measurements of Météo-France. The French national meteorological service has modelled a grid whose squared mesh is 50 km wide. Ambient temperature is available every three hours with the period 2001-2012. A database was built from the amount of gigabytes in order to perform fast queries on locations and period of time. Bicubic interpolation is used to operate with the coordinates of given location (substation or cable route) and to plot maps with isotherm areas. The available historical data are averaged to a 365 day period. A sinusoidal regression calculation gives the equation of the minimal, maximal and mean temperatures as a function of date. Considering mean features of soil (thermal resistivity, thermal capacity and density) and the heat conduction equation in semi-infinite plan, it is possible to draw trend curves of soil temperature at different depths and to emphasise the seasonal attenuation of temperature variation and time-offset for deep buried cables. A very user-friendly application software has been developed, drawing local results such as: Monotone curve of daily mean temperature (probability: 100% > min t°C down to 0% > max t°C), Bar graph of occurrences of a given temperature, Number of ranges of n consecutive days above a reference temperature, Maximum mean temperature measured during a range of n consecutive days. Data are available from south of Portugal up to North of Finland and the application can be transposed to any grid area. The authors discuss in the present paper their approach to bring refinements in the selection of ambient temperature for cable rating calculations. JICABLE E15_0090.do ocx Cable e Joint to t FFLP P Cables s for Pro ovisiona al Repa air with Quick Q Installation. Geraldo R. de Almeida (1), Gil Va asconcellos (2), Felipe Talhofer T (3) 1 - Techsys Cables Inc., Brazil, grdealmeida@ g @techsys_ca ables.com.brr 2 - Matrix Energia, Brazil, B gilvasc c.@matrixene ergia.com.brr 3:- Light SESA Braziil, Felipe@lig ght.com.br The use e of FFLP ca able "low pre essure fluid ffilled" was diiscontinued during d '90s iin this counttry due to lack of ttechnological developme ent in cabless and compo onents and hard h compettition of XLP PE cables among o others manuffacturers inte erests. Amon ng other is, fo or example, the improvem ment of techniques to locate th he oil leakss and to de evelop effecctive techniques to repa air them. Thhis work presents a developm ment that alllows to sign nificantly red ducing assem mbling time of 138kV F FFLP strait jo oint: with elimination of lead welds w to close e the casing, pre-manufa acture of paper notches, cconductor co onnection made m mechanically without prressing. Ena abling assembly and reclose r at lleast 6 hou urs. This developm ment was ca arried out in n a Brazilian n Utility (LIG GTH of Rio de Janeiro) as an alterrnative to improve the continge ency of the southern zone e of the city of o Rio de Jan neiro UG 1388kV grid. Fig - 1 cro oss section view v of joint In the fig - 1 above e is presentted a longittudinal view w of the stra ait joint cablles class 14 45kV AC 650kV B BIL where relevant pa airs of the c connector and a the pre e-fabricated notches appear to neighbo oring conne ector and joints of pape er rolls. Only these two o improvem ments in the e making of the amendment can reduce e about two hours in the assembly y. Fig - 2 assembl edjoint after IEC 60141 tests The figure above is a complete view v of the asssembled strrait joint after treatment aand before te esting AC PULSE TEST T. The most important i pa art is shown at a the ends of o the joint w where one ca an see no and IMP plumbing g welds in th his place. Th his has been n considered the most innovative parrt of this worrk. These details a and all otherr innovations s to solve th he "trouble shooting" s constitute a suubstantial pa art of this work. Key word ds Cables, Underground U , Joint, Asse embly, Provis sional repair, Contingency cy JICABLE E15_0091.do ocx Resto oring Le ead Allo oy Solde er on Cable C Jo oints forr Fluid Filled Low P Pressurre 145kV V with In ncreasin ng Press sure Cla ass. Geraldo R. de Almeida (1), Paulo o Deus de So ouza (2), Carlos Cesar Barioni B de Oliiveira (3) ; Walte er Pinheiro (4 4) 1 - TECH HSYS CABLES, Brazil grrdealmeida@ @techsys_ca ables.com.br 2 - AES ELETROPA AULO Brazil, paulo.deus@ @aes.com 3 - DAIM MON Brazil , barioni@daimon.com.br 4 - TAGP POWER Bra azil, walter.pin nheiro@tagp power.com.b br After 50 years of se ervice some fluid filled lo ow pressure cables has brought in tthis country small oil leaks in solder jointss on the cas sing and the e metal shea aths of those e cables. Insstead of repla acing the cables F FFLP the Uttilities has decided to re estore and increase the pressure c lass of the plumbing solders. For such, a Research and develo pment proje ect was spon nsored by A AES ELETRO OPAULO under AN NEEL overviiew that enab bled the devvelop a mode el to study an nd to establissh the aging of solder joints of cable housin ng and creating solution tthat increase es the pressu ure class of tthe joints as well. FIG - 1 Abacus of Arrhenius A (illu ustrated for 1ev) 1 dy and development was s planned witth accelerate ed experimen nt using the A Arrhenius theory with The stud a simpliffied physical model, wherre the solderring and the various v poss sible types off reinforceme ents were simulate ed. In the nexxt photo is prresented all ssimplified mo odels and the e system preessure contro ol as well. The testts were acce elerated with increasing ttemperature within the closed thermoodynamic de evices, as shown in n the same fiigure. FIG - 2a Sa amples beforre aging FIG - 2b 2 Samples iinside oven JICABLE E15_0091.do ocx After the e tests betwe een [0, 1000]] on [1,10,10 00 and 1000]] stations hou urs. The dataa has been treated t in Arrheniu us abacus and a extrapolated to 50 00,000 hours s [50 years] and otherr values. Th he same experime ent was used d to set up re einforcementts (next figurre). FIG - 3a De etail of reinforcement FIG - 3b Overlook of ccomplete joint The paper covers all developmen nt and prese ents the results achieved in the restorration of FFL LP with oil leaks at the cable joints. Key word ds Cables, Underground d, Joint, Assembly, Plum mbing Solder Reinforceme ent JICABLE15_0092.docx Combined Application of Diagnostic Tools for Medium Voltage Underground Cable Networks Tobias NEIER (1), Technical Advisor 1 - BAUR Prüf-und Messtechnik GmbH, Austria Condition based maintenance is an important and necessary strategy to overcome today´s challenges for the asset management of a network operator. An exact knowledge about the condition of the cable line is necessary. Therefore test and diagnostic methods are necessary, which delivers meaningful results and simultaneously are cost efficient and simple to apply. For conditions assessment diagnostics in underground cable networks, basically online and offline methods are available. Online Partial Discharge Spot-Testing can deliver information about the presence of Partial Discharge activities along the cable. Online PD Spot-testing can be used as efficient tool to support the decision making to shut-down a cable from operation in order to conduct an offline-diagnostic. The offline diagnostic methodologies of TDR, Loss Factor measurement (TD), Partial Discharge measurement (PD) and the Monitored Withstand Test (MWT) deliver information in form of measurement values that allow providing comprehensive statements on the service reliability and condition of a medium voltage underground cable including judgment on the location of a weak spot. The article describes in detail, how the applied test methods can be used to understand the condition of a cable network, in order to identify weaknesses and improve the reliability of a cable network. The combination of online-PD measurement with offline-Diagnostic is closing the gap of unnecessary cable shut downs. Case studies will explain how the technologies are applied and how clear statements and action plans for network improvements can be generated. The paper will show in detail: - A brief description of the measurement methods and why these methods have been selected A description of the whole cable condition assessment process: Starting from the selection of the cable which has to be investigated, to the collection and evaluation of the measurement data. Detailed analysis of the interpretation of the results will be explained. It will be shown, how the acquired know how can improve the condition assessment strategy Dedicated user cases will underline how the condition assessment strategy can be applied to define the improvement measures that are necessary to increase the reliability of the cable system. Available standards for the cable diagnostic JICABLE E15_0093.do ocx Loss of diele ectric sttrength of polym mers at glass trransition due to hig gh-frequ uency vo oltages in HVDC applic cations Matthiass BIRLE (1), Carsten LEU U (1) 1 - Technische Unive ersität Ilmena au, Research h Unit High-V Voltage Tech hnologies, Ilm menau, Germ many, matth hias.birle@tu u-ilmenau.de, carsten.leu u@tu-ilmenau u.de This pap per deals witth the dielec ctric stress a and breakdow wn voltage of o polymer innsulation ma aterials in HVDC a applications. The measu ured breakdo own voltage e of flat poly ymer specim men at mixed-voltage stress sshows a corrrelation betw ween the su ubordinated direct or power-frequenncy voltage and the superimp posed high-ffrequency vo oltage. At the e example off polyvinylchloride it is shhown that in spite of a homogeneous field stress local overheatin g occurs which leads to t the failurre of specim men. The overheatting is a ressult of the die electric heatting due to the superimp posed high-frrequency (kHz) highvoltage. The diffferential scanning calorimetry (DSC C - method) is used to analyze thee specimen after the breakdow wn tests. Th herefore material sample es from different points are a extractedd and examined. The DSC - an nalysis show ws that local parts of th he sample re eached the glass transittion tempera ature and cooled down after the breakd down test w with different velocities s. At mixedd-voltage sttress the DSC - cu urves show different enthalpy relaxa ation peeks compared c with high-frequuency voltag ge stress. This indiicates a diffe erent state off order in miccroscopic strructure of the e polymer in the viscoela astic state (tempera ature higher then glass trransition tem mperature). Further high-resolution current and voltage e measurem ment signals during the glass trans sition are presente ed. Thus a sinusoidal s hig gh-frequencyy voltage is used with co omplex calcuulation the change c of the relattive permittivvity and the e resistance of the sam mples is calc culated baseed on RC - electrical equivale ent circuit (se ee Fig. 1). At the viscoela astic state the permittivity y of polymerss is higher caused by the addittionally moving of main chains. c Comp pared to high h-frequency voltage stresss the measurements and calcculations sho ow that the change c of pe ermittivity durring glass tra ansition is loower at mixed-voltage stress. T The change of the electrric resistance e implies the e polarization losses andd losses by electrical conductivity. After pa assing glass s transition th he electrical strength of the materiaal is decreased which leads to a breakdown n. Fig. 1: m measured tem mperature of the sample and change of permittivitty and resistaance during glass transition n JICABLE15_0094.docx On-line Monitoring and Relative Trending of Dielectric Loss in Cross-Linked HV Cable Systems. Yang YANG (1), D. M. HEPBURN (1), Wei JIANG (3), Bin YANG (3) Chengke ZHOU (1), Wenjun ZHOU (2) 1 - Glasgow Caledonian University, Glasgow, UK, Yang.Yang@gcu.ac.uk, D.M.Hepburn@gcu.ac.uk, C.Zhou@gcu.ac.uk 2 - Wuhan University, Wuhan, China, wjzhou@whu.edu.cn 3 - Wuhan Power Supply Company, Wuhan, China, 1458172995@qq.com, 84916067@qq.com Worldwide, to meet growth in electricity consumption and ensure power supply security, increasing volumes of cross-linked polyethylene (XLPE) high voltage (HV) cables are adopted in transmission and distribution networks. So it is of increasing significance to improve the reliability and operational safety in HV cable system which mainly consists of three-phase, cross-bonded when circuit length exceeds one Kilometers, single-core XLPE HV cables. Meanwhile, on-line monitoring provided an advanced way to achieve condition monitoring (CM), which reflects equipment operating status in real time effectively and realistically. As a characteristic factor reflecting the general state of cable insulation, Dielectric Loss (DL) has been studied and reported widely throughout the world. Although DL is acknowledged as an important indicator of cable deterioration, it is necessary to take the cable off-line to carry out the test. There is no published work indicating achievement of on-line monitoring of DL in a cross-bonded single-core XLPE HV cable system. Cross-bonded single-core HV cable system, a good solution to the problem of induced voltage in metal shields, brings additional challenges to on-line monitoring, e.g. in measurement of Partial Discharge (PD) and DL, because the electrical connection of the three phase shields makes it is difficult to extract the useful signals from the detected signals. A new method, Leakage Current Separation Method (LCSM), is proposed to separate the insulation leakage current from the detected signals which contain circulating current. Clamp-type power frequency current transformers (CT), selected as measuring devices, were installed at the four cable link boxes (shown in Figure 1). Analyzing the synchronously acquired current signals of twelve CTs installed at the connection boxes allows LCSM to distinguish leakage current of each cable section. A comprehensive DL trend analysis was proposed, without detection of a reference voltage signal, a factor widely applied in the computing DL. DL trend analysis gives a new way to describe the three-phase cable system deterioration by judging the relative DL between phases. As the three cables are affected by the same environmental and operational stresses, detecting difference in leakage current is an effective method to compare the relative dielectric loss. If degradation or a fault occurs in one phase of the system, the DL of this phase would change relative to the other phases in a short time. Deterioration of the cable system could be judged without a reference voltage, which is a challenge in practical detection systems. A model of a three-phase single-core XLPE HV cable system will be studied and deterioration criterion will be shown. In addition, error analysis of the measurement and inflection factors will be discussed. JICABLE15_0094.docx Connector Connector Phase A Metal Shield Core Phase B Insulaiton Phase C JD1 JX1 JX2 CT Grounding box Cross-bonded connection box CT JD2 Grounding box Fig. 1: CT location in cross-bonded XLPE HV cable system JICABLE E15_0095.do ocx Produ uction, installa ation an nd com mmissioning off two 380kV 3 underground d lines for the e Pump p-Storag ge Plan nt proje ect of Linth Limme ern (Swis ss Alps)) Claude B BIOLLEY an nd Christian MOUCHANG M GOU Nexans Suisse SA, CH C 2016 Corrtaillod claude.b biolley@nexa ans.com, christian.mouch hangou@nex xans.com Axpo (a Swiss DSO) is currently y completing a 1GW Pum mp Storage Plant projectt in the centtral Swiss Alps, in tthe region of the Limmern lake. Thiss plant will work between the 50 yearr old Limmerrn dam at 1850 m meter of altittude (480MW installed ) and a na atural lake (Muttsee) aat 2470 me eter. The undergro ound power plant will be e connected to the grid via two 380kV undergroound feeders s and our team is iin charge of the fabrication, the insta allation in the e tunnels and d the commisssioning of these t two lines. The diffe erent challen nges of the project lie in the fact that t the 380 0kV-1600mm m2 copper ca ables are installed in a cable-ccar tunnel, ex xhibiting a sttiff incline (25%), with ve ery little room m (1.2 meter wide) for the 420kkV joint installation. This pap per will desccribe the tec chniques de eveloped for the cable laying, includding the des sign of a specific laying syste em, the jointer training for the 420 0kV junction preparationn in such a confined environm ment, and th he required work w organizzation able to t keep the project timinng on track while the cable ca ar was runnin ng at full capa acity for the m material tran nsportation. Another difficulty wa as to guaranttee the clam mping of the cables in su uch an inclinne; a specific c solution which ha ad to be developed, teste ed in therma al cycles and validated in our labs willl also be des scribed in this pape er. F Fig.1a Loadin ng of the laying bench on the e cable car lo orry Fig.1b 380kV cablee installation in the tunnnel JICABLE15_0096.doc Cable replacement in a generation plant Patrick JORAND, Fabrice MOUSSET, Yves MAUGAIN (1), Mehdi OUENZAR, Hervé GUYOT (2) 1 - EDF CIST 2 rue Michel Faraday 93200 Saint Denis France - patrick.jorand@edf.fr , fabrice.mousset@edf.fr , yves.maugain@edf.fr 2 - SPAC agence Clichy, 13 rue Madame de Sanzillon 92110 Clichy France - ouenzar@clichy.spac.fr , guyot@clichy.spac.fr EDF Generation Division manages in France 370 output substations located in generation plants. The thermal power plant, Le Havre, in Normandy, was composed of 4 units, three of them being coal-fired, the last one being fuel-oil fired. It was decided to extend the lifetime of the 600 MW coal-fired unit #4 commissioned in 1983 up to 2035. As this unit will be the only one staying in operation on the site in the coming years, it was decided to guarantee the feeding of the auxiliary system through a cable system up belonging to EDF from a GIS belonging to the TSO, RTE. This was done by using the cable route of unit #3 output commissioned in 1973, presently definitely out of service. After a cable expertise, it was decided to replace the 40 years old cable during the main refurbishment of the power plant to be sure to cope with the end of life of the power plant. The initial cable was an OF cable with a 6 bar internal pressure. As it is more and more difficult to maintain this type of cable technology due to the important reduction of expertise, spare parts and of maintenance teams able to deal with, it was decided to guarantee the reliability of the auxiliary connection by changing the existing cable to a 225kV 400 mm² aluminum XLPE cable system. The paper will describe the main problems faced to replace this cable: To work in an overcrowded and limited space with up to around 1500 workers during the peak period To lay cables in the old fuel storage where the soil was polluted To find the best cable construction technique and installation design according to the route allowed by the thermal generation engineering unit, crossing the foundations of the existing power plant, using cable trays where existing LV and telecom cables where already laid To adapt the cable termination to the existing GIS in RTE substation. To find solutions at the transitions between the different construction techniques and between rigid and flexible installation. To reach the goal “0 accident” despite the difficulties mentioned and the use of specific and heavy equipment (crane, winch, mechanical digger…) Compared with cable works in TSO networks, this installation was really difficult and unusual. Key words: Cable installation, generation plant JICABLE15_0097.docx Lifetime extension of medium voltage cables Rudolf WOSCHITZ (1), Alex PIRKER (1), Herbert STEURER (2), Martin HESSE (3) 1 - Institute of High Voltage Engineering and System Performance, Graz University of Technology, Austria, woschitz@tugraz.at , alex.pirker@tugraz.at 2 - Netz Burgenland Strom GmbH, Eisenstadt, Austria, herbert.steurer@netzburgenland.at 3 - UtiLX Europe GmbH, Bückeburg, Germany, martin.hesse@cablecure.de In many Austrian distribution grids PE-insulated medium voltage cables installed in the 80’s are still in service. Failures caused by water-trees in the insulation are well known and reported. For grid operators this raises the question of whether to replace the cables to maintain the reliability of the grid. Another possibility instead replacing those cables is to extend the life time of PE-insulated cables using a treatment to refit the insulation. This treatment uses a silicon based fluid which is pressed into the insulation of the cable to inactivate existing water trees. At the beginning cables have been treated using a fluid with components of phenylmethyl-dimethyloxysilane. These components often caused accelerated corrosion of aluminium conductors because of chemical reactions. Due to this fact a couple of years ago the fluid was improved using alkoxylane to prevent corrosion. In cooperation with the Austrian Netz Burgenland Strom GmbH, the German UtilX Europe GmbH and the Institute of High Voltage Engineering and System Performance, Graz University of Technology, the effectiveness of this improved method for life time extension of medium voltage cables has been investigated. For that purpose sections of 20kV cable lines have been cut out of the grid right before the beginning of the treatment to refit the insulation. The optical investigation showed that all samples contained water trees. Cables with PVC sheath had very high moisture content and showed water droplets between copper screen and sheath. The lightning impulse tests on samples with PVC sheath showed remaining withstand voltage levels in the range between 250kV - 325kV. Samples with PE sheath showed remaining withstand voltage levels in the range between 375kV - 450kV. To evaluate the effect of the treatment 10 month later refitted samples of cables have been investigated as well. The optical investigation showed not any water trees and the increase of the withstand voltage level was significantly. The lightning impulse tests on samples with PVC sheath showed withstand voltage levels in the range between 425kV - 475kV. Samples with PE sheath showed withstand voltage levels in the range between 500kV - 525kV. Comparatively the withstand voltage level of 20kV XLPE-cables straight from the manufacturer is in the range between 600kV - 700kV. KEYWORDS Medium voltage cables, PE-insulated cables, life time, refitting of PE-cables, water trees JICABLE15_0098.doc Mechanical Connectors used inside M.V. Accessories: a system approach. Dario QUAGGIA (1), Stéphane TOGNALI (2), Gérard LENCOT (3) 1 : Prysmian S.p.A. V.le Sarca, 222 (F.307-HQ) Milano-Italy, dario.quaggia@prysmiangroup.com 2 : Prysmian S.p.A , stephane.tognali@prysmiangroup.com 3. Prysmian S.p.A Champs sur Marne -Marne la Vallée France, Gerard.lencot@prysmiangroup.com The so called Mechanical Connectors (MC), mainly using the shear-bolt technology, are now widely used inside the Medium Voltage Accessories to connect the cable conductors. The major advantages of these devices for the end user are the wide “range-taking” (i.e. one MC is suitable for covering a range of cable conductors) and the “tool-free” solution (i.e. no heavy tools are necessary on site for the connectors application). Consequently, an important reduction of inventories and number of models is also possible. For the above reasons MC become very popular and well accepted by the jointers, as well as the purchasing and logistics managers. In parallel Cold Shrink (CS) accessories have demonstrated their reliability in many years of service, as well as their ability to cope with different types of cables and network configurations. CS accessories, with their wide range-taking, have the same advantages of MC in terms of jointing simplification, reduction of inventories and reduction of number of models. This is why assemblies “MC+CS” are thoroughly used by mainly utilities around the world. However, the large number of suppliers of MC showing a very variable level of quality and design is posing a problem of choice and selection for the manufacturer of accessories, and consequently for the end user. Indeed, despite the fact that the connector itself had passed severe individual tests (IEC 1238) it was found many shortcomings during the Accessories type tests using some types of MC. Problems coming from MC had not been identified during the specific tests of the connectors, but occurred both using CS accessories and traditional single-size accessories. This is why it is so important to consider the couple “connectors + accessories” as a system. In this paper, after brief historical review of the technology and the advantages of the MC we will show how the behavior of MC is different as an independent device and inside an accessory, and also when MC is submitted to other stresses than those usually tested in the stand-alone connector specification, which is often the case on the field. We will demonstrate the technical risk to use an improper MC, showing the results of tests in different configurations and explain why it is preferable for all the supply chain to leave the choice -and the responsibility- of the MC to the accessories manufacturer. Legend: MC= Mechanical Connectors; CS = Cold Shrink technology Key words Mechanical Connectors; Cold-Shrink; Medium Voltage Accessories JICABLE15_0099.docx Optimization of High Voltage Electrodes and HV Cable Accessories Design By Using MATLAB and FEMM Enis TUNA (1) 1 - Demirer Kablo, 4 Eylül Mah. İsmet İnönü Cad. No:279 Bilecik / Turkey; enis.tuna@masscable.com As a response to an increasing demand for electrical energy, transmission voltage levels have increased drastically over the last years to optimize transmitted power on the transmission lines.With the increased voltage levels designers are forced to optimize field control elements on cable accessories with the goal to achieve smooth and linear field distributions to use the material closer to theoretical lifetime expectations.To accomplish this,most important thing is understanding of insulating material properties and having knowledge for electric fields and the ways of controlling electrical stress. Electrical field lines distribution, behaves according to electrodes physical condition (physical position according to each other) which this also leads to assessing dielectric strength. In this study, three electrode gap types are simulated and simulation results of three electrode configuration are reported. According to mathematical optimizations, high voltage accessories stress control elements are produced by taking into account field simulation reports. To calculate the field distribution between electrodes, FEM (Finite Element Method) is used with the 2D simulation program FEMM. Optimization on the electrode shapes and defining the border conditions is done with MATLAB. In order to create an uniform field in the gap between electrodes, numerical experiments with mathematical equations are used with included main parameters like gap spacing, overall diameter (overall diameter for cylindrical systems etc.) In three electrode configuration; computed electric fields on the surfaces indicated the differences and non-uniformaties in electric fields and also helped to comparing three electrode gap configurations named, Parallel Plane Profile, Rogowski Profile and Borda Profile. Optimized profile equations by MATLAB; are used to define the physical coordinates of those profiles. After simulation and optimization the practical implementation was finally done for High Voltage cable accessories used for field control in cable connectors as joints and at cable stresscone as various types of sealing ends. In this study, it is shown how to transfer optimized electrode shapes from mathematical equations coming from MATLAB into CAD drawing and FEMM design drawings in the most efficient and easy way and how the correlation between MATLAB and FEMM is used during this optimization process. Keywords: high voltage cable accessories, MATLAB, FEM, borda profile, non-uniform field, Weibul distribution, lifetime JICABLE15_0100.doc Worldwide experiences and challenges with EHV XLPE cable projects 330kV to 500kV Andreas WEINLEIN (1), Ulrich PETERS (1), Uwe LAAGE (1), Horst MEMMER (1) 1 - Südkabel GmbH, Mannheim, Germany, andreas.weinlein@suedkabel.com , ulrich.peters@suedkabel.com , uwe.laage@suedkabel.com , horst.memmer@suedkabel.com With an experience of more than 1,300 km underground XLPE cables and more than 2,650 sealing ends (almost 1,700 joints) for operation voltages 330 - 500kV over a period of 20 years, the technical solutions and concepts for development, manufacture, assembly, testing and operation are largely confirmed. Concepts are introduced and the advantages and disadvantages are balanced compared to other directions of development. As a special highlight of the EHV cable technology one of the longest 500kV cable systems installed in Moscow (Russia) is described with its current operating experience. After a rather short project running time of less than 17 months between order intake and commissioning the project has been completed in May 2012. A total amount of 70 km 500kV XLPE cable, 138 joints and 12 outdoor terminations have been manufactured, delivered, installed and commissioned successfully for the customer FSK-Meszentra (Russian National Grid Company). The project was planned in order to replace a 11 km long 500kV double system overhead transmission line. The cables which are laid in trefoil in ground show a conductor cross section of 2500 mm², an insulation thickness of 28 mm, copper screen wires and a laminated HDPE sheath. Radial water protection is ensured by a 0.2 mm thick laminated aluminium foil whereas the HDPE sheath delivers the mechanical protection during installation and operation. This sheath design delivers a very slim cable design with optimised screen losses and is well accepted in several countries for decades. The conductor consists of oxidized wires to reduce the skin effect losses. With the chosen laying arrangement this allows a rated continuous power transmission of 860 MVA per cable system. The joint design of one-piece type joints made from silicone rubber has an integrated screen separation section to allow both, cross bonding and single point bonding applications. The joint corrosion protection design consists of a rigid glass fibre re-enforced plastic housing which is filled with cast resin. The design has been qualified according the IEC 62067, annex G requirements as well as the extensive mechanical loading test followed by a water immersion test acc. to NGTS 3.05.02 requirements. The outdoor termination design is based on the dry plug-in termination which is integrated into a pre-fabricated and pre-tested gas-filled bushing. This design allows a short installation time and avoids any liquid fillings. This type of termination was adapted to the extreme temperature conditions of the Moscow region by an external heating system. The AC voltage commissioning test has been carried out by applying the series resonant testing principle. In order to generate the required testing current of 120 A at a testing voltage of 320kV five testing modules were operating together. The installation quality was checked by using inductive type PD sensors temporarily installed at the cable screen. High reliability, reduced repair times and decreasing cable and accessory prices make the EHV XLPE cable system competitive with overhead lines, especially in difficult terrain or environment, urban areas, industrial plants and with high land prices. In addition to the major projects with large system lengths in metropolises such as currently installed in Moscow and London, cable projects in the most remote regions of the world, very often connections within cavern hydropower plants between main transformer and switchgear, require a very high wealth of experience in design, grounding concepts, transportation as well as in laying and fixation concepts. In contrast to alternative cable designs with e.g. enamelled wires, the oxidized wires allow jointing of the conductor without special treatment of the single wires, which accelerates the overall jointing, while still gaining from the same ks-factor improvement. The laminate sheath design likewise allows for a resilient and easy handling of the screen on site for cable layings and accessory installations compared to lead or thick aluminium sheaths. JICABLE15_0101.doc Long-term experiences and review with offline and online PD measurements on-site on EHV XLPE cable systems 330kV to 500kV Andreas WEINLEIN (1), Ulrich PETERS (1), Gero SCHRÖDER (1), Dominik HÄRING (1) 1 - Südkabel GmbH, Mannheim, Germany, andreas.weinlein@suedkabel.com , ulrich.peters@suedkabel.com , gero.schroeder@suedkabel.com , dominik.haering@suedkabel.com A high voltage cable is tested to demonstrate the guaranteed properties, to show the compliance with standards and to secure the operating reliability. For an XLPE cable the essential tests are the AC voltage test and a partial discharge (PD) measurement. A solitary voltage test has the shortcoming of not detecting all irregularities which may harm the operating reliability by causing a breakdown during voltage test time while at the same time not initiating pre-damages at irregularities which otherwise would not harm operating reliability. The solution for such a sensitive test method is the PD measurement. Commissioning tests are carried out on the assembled cable system once the installation is completed. There are very few tests that can be carried out that will prove the long term life of cable and accessory. The relevant standards for high-voltage cable systems (IEC 60840 / 62067) recommend two possible after installation tests: As all prefabricated components are factory tested, a DC measurement of the outer sheath together with a quality assurance procedure during installation. In reality, this possibility is not taken into consideration by customers. De facto an AC voltage test of the main insulation with a specified value (1.7·U0 or values acc. to table 4 column 11 in IEC 60840 / 62067) for 1 hour or U0 for 24 hours (‘soak-test’) is carried out. In addition to the tests specified in IEC 62067 the manufacturer recommends and practises a PD measurement of all accessories after installation for voltage levels Um ≥ 362kV. The experience of about 2400 tested EHV accessories during commissioning or system assessments in about 170 assignments all around the word was cumulated the last 12 years. Summing up it can be evaluate that for a reasonably commissioned EHV cable system including PD measurement no further monitoring facilities are necessary like for example a continuous PD measurement system. Considering the costs of such systems of up to 15% - 20% of the supply share of cables and accessories this expenses should be invested in a well done PD measurement during commissioning, not yet taking into account the flood of data and the necessary fast and qualified response on actual occurrence of PD detected by such a monitoring system. JICABLE15_0101.doc Ideally the test is carried out using an AC resonant test set. This allows the cable system to be energised offline and at low energy and so there is a minimised risk of breakdown. It is also possible to carry out an AC test by energising the system with system voltage and using online partial discharge monitoring. This is not ideal, as noise from the system can mask discharge activity occurring within the accessory. In addition, if a breakdown does occur this will lead to a disruptive failure of the accessory and may lead to an outage and power disruption. Very often for new installations as well as for system assessments it is possible to carry out online measurements in isolated operation with the feasibility of increasing the voltage up to 110% via the generator. For these measurements a huge expert knowledge on-site is necessary to be able to compare and evaluate the accessories vertically and horizontally inside a system. The requirement to carry out such online measurements globally by the cable system manufacturer is the availability of a modern, robust and finally compact PD measurement equipment for on-site use which can be carried along by the test engineer worldwide. Current considerations using alternative voltage types for high voltage commissioning tests of EHV and HV cable systems are regarded as very critical. DC voltage tests must be considered with respect to a potential risk of damaging the insulation system. For example DAC (damped AC) or VLF (very low frequency) are non-standard-compliant test methods. These test methods are not comparable to power-frequency voltage tests or operation similar frequencies (10-300 Hz). In the overall context these methods do not correspond to the state of the art and knowledge and have to be rated accordingly. On the other hand the behaviour of some breakdowns during operation indicates a gap in today's testing philosophy that does not seem to be filled out with the diagnostic methods available today. JICABLE15_0102.doc AC resistance measurements on skin-effect reduced large conductor power cables with standard equipment Gero SCHRÖDER (1), Dominik HÄRING (1), Andreas WEINLEIN (1), Axel BOSSMANN (1), Ronald PLATH (2), Markus VALTIN (3), Maitham MAJID (4) 1 - Südkabel GmbH Mannheim, Germany; gero.schroeder@suedkabel.com 2 - Ing.-Büro HPS Berlin, Germany; rplath@hps-berlin.de 3 - Electronics - Web and More GbR, Germany; valtin@e-wam.de 4 - Balfour Beatty Utility Solutions, United Kingdom; Maitham.Majid@bbusl.com The increasing demand for HV/EHV cables with very high ampacity require conductors having large cross sections. Furthermore cable conductor designs with low impact of skin effect become more and more relevant to minimize additional losses caused by the conductor AC resistance. For this reason improved conductors designs with special features e.g. additional insulation between the stranded wires, oxidised or enamelled wires are used in order to reduce the skin effect. Actually the international standards IEC 60840 and IEC 62067 require the identification of cable characteristics. In terms of AC resistance the presence, if any, and nature of measures taken to reduce skin effect shall be declared. If so, one approach to do this is an ac-resistance measurement in order to verify the specified properties of the cable. At the moment the measurement procedure is not standardized, but a generally accepted method to describe the behaviour of the skin effect and eddy current losses is the expression by the well known ks-factor, as describe in the international standard IEC 60287 AC resistance measurements on full size cables produce plausible results, but the execution of these measurements are difficult to apply under practical conditions. Measurements on short cable samples are easier to execute, but they tend to be more sensitive regarding the measurement inaccuracy. The use of a suitable test set-up and adequate connectors as well as a general understanding of influencing factors are mandatory to understand and interpret measurement results. To utilize the full abilities of reduced skin effect of conductors and to ensure the quality during production new measuring techniques are needed, which are both, easy to handle and good in accuracy. Here, the used procedure is based on high-accuracy vectorial voltage-current measurement. The current flow is coaxial using the cable screen as the current return path, avoiding any cable-external magnetic field. Thereby, the proximity effect by the parallel conductor is excluded. By performing the AC resistance measurement with variable frequency it becomes possible to self-check the measurement results with data from calculations and other measurements. For instance a measurement with a frequency very close to 0 Hz deliver results that can be double checked with other equipment e.g. DC test apparatus. This paper reports about progress and experiences of the development of a new and available measurement system in order to determine the AC resistance of cable conductors with large cross sections having a reduced skin effect. Investigation results and plausible verifications show, that the new measurement system is suitable to use and determine the ac resistance respectively ks-factor. The influence of cable screen constructions, e.g. screen wires or aluminium metal sheath, measurement set-up and conductor temperature have been investigated in the meantime. Measurements have been done in different configurations and show the influence of the mentioned influencing factors. Studies about influence and behaviour of the magnetic flux inside and outside of the cable during the execution of a measurement back-up the results and are very useful for a general understanding. JICABLE15_0103.doc The Oslofjord Project - The world's first installed 420kV submarine cable connection combining SCFF cables and XLPE cables with flexible factory joints Frøydis OLDERVOLL (1), Geir Olaf JENSEN (1), Stein Arne SLÅTTEN (2), Josten ELDERS (2), Einar KALDHUSSÆTER (2) 1 - Statnett SF, Cable Technology Department, Oslo, Norway, froydis.oldervoll@statnett.no , geir.jensen@statnett.no 2 - Nexans Norway AS, Oslo, Norway, stein_arne.slatten@nexans.com, Jostein.elders@nexans.com, einar.kaldhussater@nexans.com Statnett commissioned and put into service a new 420kV AC cable connection across the outer Oslofjord in 2014. The crossing south of Horten and Moss is 13 km long and has a water depth of maximum 220 meter. The cable system is based on a dual technology concept with six paper insulated self contained fluid filled (SCFF) cables with state of the art pumping stations on both sides of the fjord and three cross-linked polyethylene (XLPE) cables. Each XLPE cable contains two factory joints fully qualified and type tested. To our knowledge this is the world's first installed 420kV XLPE submarine cable system with flexible joints. Nexans Norway AS was awarded the turn key contract for the Oslofjord project 3rd May 2010. In this project Statnett decided to combine the well known and proven SCFF technology with the emerging XLPE technology. The motivation for this choice was to start accumulating service experience with the XLPE technology for 420kV while keeping the risk level acceptable for this connection that is a vital part of the grid in the Oslo area. The SCFF technology has a long track record for submarine applications and has proven to be very reliable. The XLPE cable with accessories was type tested and routine tested according to requirements given in IEC 62067 and Cigre recommendation Electra No. 171 and 189, while the SCFF cable with accessories was type tested and routine tested according to IEC 60141 and Electra No. 171. Mechanical tests were carried out for a design water depth of 400 meter. This ensured a robust margin with respect to the actual maximum laying depth of 220 meter. A Distributed Temperature Sensing Systems (DTS) with fibre optical cables integrated in the power cables was installed to monitor the temperature of all nine cables from cable end to cable end. This ensures that the operational temperature on critical sections of the cables is within specified maximum allowable. As part of the contract, Nexans delivered two complete pumping plants to supply oil and maintain pressure for the SCFF cables, one for each side of the fjord. Each pumping plant has the capability of supplying all six cables thus providing redundancy in case of service or repair on one side of the connection. In case of rupture of the SCFF cable, the pumping plant can maintain the oil pressure in the cables without ingress of water for a certain time until repair. All characteristics of the pumping plant and the cable system are monitored from the Statnett regional control center securing a short response time in case of irregularities. The cables were installed using the cable laying vessel Nexans Skagerrak. The cable route was challenging with steep and rocky slopes down to the bottom of the fjord and narrow cable separation in the shallow areas, thus high precision positioning was required during the cable laying. The cables were as far as possible trenched to 1 meter depth in the subsequent trenching operation in order to protect against trawling activities in the area. JICABLE15_0104.doc Development Process of Extruded HVDC Cable Systems Dominik HÄRING (1), Gero SCHRÖDER, Andreas WEINLEIN, Axel BOSSMANN 1 - Südkabel GmbH, Mannheim, Germany, dominik.haring@suedkabel.com Extruded HVAC cable systems up to 500kV have been successfully developed in the last decades and several years of operating experience are available. Because of an increasing power demand and the requirement to transmit electrical energy over long distances, HVDC cable systems become more important in cable industry and energy grids. However, due to the DC stress new development activities of extruded HVDC cables and accessories are necessary in terms of design and material for a reliable energy supply in the future. Reasons for this are the strong influence of space charge accumulations in the insulation system, strong dependence of the materials regarding temperature and field strength, and the inversion of field gradient of loaded cable systems. These differences require a special consideration of the components under DC conditions under all possible operation stages regarding temperatures and applied voltages. After evaluation of the DC influences to the cable and accessories of a HVDC system, a cable system in model scale has been developed and tested. The model scale cable system is based on a 80kV voltage level. General design parameters for the model scale cable system have been taken from well known HVAC cable systems. However, special materials and design details have to be implemented to withstand the DC specific influences. The tests have been carried out in adaptation to CIGRE recommendations. An adapted type test has been carried out and passed successfully. After completion of the tests on the model scale cable system, a 150kV HVDC cable system has been developed. Design parameters of the model scale system have been adapted to the 150kV system. Development tests shows the suitability of the designed 150kV HVDC cable system. A type test in adaptation to CIGRE recommendations has been carried out and passed successfully. An internal long-term test is in progress and the successful completion of this test is expected. Further considerations regarding external long-term tests are ongoing. Furthermore, the development of a 320kV HVDC cable system is planned. This paper addresses the influence of DC stresses on the components of HVDC cable systems. Fundamental aspects regarding the interface between cable and accessory will be discussed. The paper describes the development process of an extruded HVDC cable system from beginning of a prototype system to a commercial HVDC cable system from the view of a cable system manufacturer. JICABLE15_0105.doc Life Cycle Assessments of Extruded AC and DC Power Cable Systems Dominik HÄRING (1), Gero SCHRÖDER, Christoph SAAM, Andreas WEINLEIN, Axel BOSSMANN 1 - Südkabel GmbH, Mannheim, Germany, dominik.haring@suedkabel.com The growing industrialization requires an increasing responsibility of industry and manufactures for its influence on environmental impacts. Electric power cables take a fundamental part in distribution and transmission of electrical energy for a reliable energy supply in the future. Higher power ratings require higher system operation voltages and currents. Power cables with weights up to approx. 60 kg/m are necessary to meet those requirements of the increasing energy demand. This shows, that the question of sustainably manufactured products like power cables is appropriate. However, because of a complex and complicated production process, the analysis of the environmental impacts of a cable manufacturing process needs a detailed investigation of the used materials, processes and operation stages. For a sustainable manufacturing of power cables a life cycle assessment (LCA) is helpful. LCA is a systematic investigation of a product and its environmental impacts. The system boundary of a LCA depends strong on type of product and the available information and data. This paper describes a developed method to investigate the environmental impacts of a cable manufacturing process. The main focus of the LCA is on the carbon dioxide footprint and energy demand. In a first step the production of raw-materials used for the cable manufacturing has been analyzed. Several data and information have been collected and evaluated. Those data are the basis for further considerations of the LCA. In a second step, each production stage in the cable manufacturing process has been investigated. Detailed measurements of the energy consumption of each process have been carried out and analyzed. Thereby, the focus is on the energy-intensive processes as stranding, extrusion, tempering, sheathing, and testing. The obtained data and information have been evaluated and translated in a carbon dioxide footprint. The result of the production LCA will be discussed. The investigation of the environmental impacts of a cable manufacturing process has been carried out on two different cable types. Thereby, at first a HVAC power cable of type 2X(F)KL2Y 1x2500 RMS 300kV has been investigated. In a second step a HVDC cable with similar geometric dimensions and weights has been investigated. The developed LCA of both cable types enables a general comparison between the manufacturing process of HVAC and HVDC cables. The differences between HVAC and HVDC cable manufacturing will be discussed and evaluated in terms of a sustainable development process for new products. Furthermore, fundamental considerations regarding the environmental impacts during the operation stage of a cable system have been carried out. The main focus is on the magnetic fields and influences caused by the conductor temperature of the cables. Both considerations have been carried out and compared for HVAC and HVDC cable systems. JICABLE E15_0106.do ocx Therm mal Ratting Me ethod o of J Tu ubes us sing Fin nite Ele ement Analy ysis Tec chniques s Richard CHIPPENDA ALE(1), Priank CANGY ((1), James PILGRIM(1) P 1 - Tonyy Davies High h Voltage Laboratory, Un niversity of So outhampton, Southamptoon, UK, oton.ac.uk, jp p2@ecs.soto on.ac.uk rd.chippendale@ssoton.ac.uk, pc8g11@so The insttallation of offshore wind d farms pressents a uniqu ue set of cable challengges which ne eed to be considerred, as com mpared to standard o on-shore ca able installations. Somee areas off special considerration are th hermal rating g methodolog gies, mecha anical protecttion of cablees and conn nection of supply to o land. This study investigates the tthermal profile of the exp port cable fro rom a wind farm f as it passes tthrough the J tube of an offshore plattform. This section s of the e cable routee may often present p a limit on tthe current carrying capa ability of the w whole route. Whilst th here are pub blished standards to pre edict the the ermal rating of a buriedd cable, therre are no internatio onally agree ed standards s for predictin ng the therm mal rating of an export ccable within a J tube. Thereforre this study has conside ered a series of modeling g approaches s to investigaate the therm mal profile within the J tube. The study has initially develop ped a 3D fifinite elemen nt analysis (FEA) modeel to investiigate the temperature profile within w a typical J tube. Th he J tube is comprised c of three main ssections: 1) Below sea le evel, where the gap betw ween the J tub be and cable e is filled withh water 2) A Above sea le evel but belo ow the offsho ore platform, where the ga ap between tthe J tube an nd cable iis filled with air a he individuall phases from 3) A Above the offfshore platfo orm, where th m the export cable are se eparated a and installed d in air A typical conductor profile from this model iis presented d Figure 1, and a shows thhat the therm mal pinch point witthin a J tube e occurs in the middle J tube sectiion, between n the sea leevel and the offshore platform. Below sea level Above platform p Above s ea level, b ut below p platform e profile within J tube. Figure 1 - Conductorr temperature This incrreased temp perature is ca aused by the e sealed air gap g between n the cable aand the J tub be, which acts as a good therm mal insulatorr. Any solar rradiation incident upon the J tube suurface will als so play a significant role in increasing the conductor c te mperature within w this sec ction. The theermal performance of the J tub be has been n further inve estigated by varying the length of ea ach J tube seection, the conductor c and the J tube cross sectional area. JICABLE15_0106.docx This more physically rigorous 3D FEA model is then compared against a selection of previously published analytical methods [1, 2] for predicting the continuous thermal rating. By comparing the FEA model with these previous studies it is evident that there predicted ratings are not in close agreement with the FEA results. Therefore an improved method has been developed to predict the continuous rating, which is presented in this paper. References [1] R. A. Hartlein and W.Z. Black, "Ampacity of electric power cables in vertical protective rises", IEEE transaction on power apparatus and systems Vol PAS-102 no.6 June 1983 [2] M Coates, "Rating cables in J tubes", ERA technology, report number 88-0108 JICABLE15_0107.docx Cables for Oil, Gas and Petrochemical Industry Arun THOMBRE (1), Bahaa MOURAD (1) 1 - DUCAB, Dubai, UAE, arun.thombre@ducab.com, bahaa.mourad@ducab.com Cables in Oil Gas & Petrochemical (OGP) environment are designed to face the brutal attacks of chemical products consisting of acids, bases and different hydrocarbons. As an age old practice and established design, a seamless lead sheath in the form of extruded tube is provided over laid up cable. The chemical composition of lead is based on BS EN 12548 and the alloy requirement. The most popular alloy being PB021K (earlier known as Lead alloy E). The lead sheath thickness is arrived at as per the EEMUA 133 specification in case of LV cables and IEC 60502-2 fictitious method for MV cables. The lead sheath is acceptable practice and time tested design over the years. Being metal, lead sheath also offers conducting path to share the earth fault current when required. Some of the clients require an alternative to lead sheath design when conducting path is not essential. In order to cater to these requests, we have come up with an alternative design. The new designed cable consist of three construction elements in layers for providing complete protection as mentioned below. Polymer laminated AL tape applied longitudinally to provide radial barrier for various fluids HDPE sheath which is resistant to inorganic chemicals and Polyamide sheath (also known as Nylon layer) which is resistant to organic chemicals and hydrocarbons These three layers are applied in co-extrusion process making strong bond for fighting against chemical attacks faced in OGP environment. ‐ ‐ ‐ Polyamide is well known for providing hydrocarbon and chemical resistance. It is suitable for functioning at cable operating temperature. It exhibits good flexural modulus and offers low permeability of hydrocarbons and fuels, maintaining the main physical and chemical properties in the finished cable. Thus the OGP industry gets wider range of choice and cable designs for application. These cables are designed to meet, ‐ IEC 60332-3 flame retardant tests in cat A / B / C as per design ‐ Hydrocarbon resistance ‐ Low toxicity A general comparison between Lead sheathed and Polyamide sheathed cable is as per the below table No. Parameter Lead sheathed cable Poly-amide sheathed cable 1 Protection against Hydrocarbons Yes Yes 2 Weight Heavier Lighter 3 Bending radius Little larger Smaller as compared to lead sheathed cable 4 Electrical conducting path for earth fault Yes, available No, not available 5 Terminations Standard Standard 6 Number of layers One Combination of three layers This paper will examine specific comparisons based on real cable design examples for the readers to get extra details on the two types of cable designs. Cable cross sectional drawings will be incorporated for easy comparisons. JICABLE15_0108.docx Type testing of 150kV / 161kV cable system combining AEIC, ICEA and IEC test requirements Ivan JOVANOVIC (1), Georgos GEORGALLIS (2), Constantinos CONSTANTINOU (2), Grand WU (3) 1 - G&W Electric Company, Bolingbrook, USA, ijovanovic@gwelec.com 2 - Hellenic Cables SA, Marousi, Greece, ggeorgal@cablel.vionet.gr , cconstan@cablel.vionet.g r 3 - G&W Electric Company, Shanghai, China, Grand_Wu@gwelec.com.cn In today’s global HV and EHV power cable system segment, there are number of different standards and specifications for qualifying cables and cable accessories, and they usually come with different sets of testing requirements and relatively low level of harmonization between them. In order to feasibly qualify the products by minimizing testing costs and time, manufacturers are increasingly trying to consolidate different testing protocols and optimize testing procedures. This process is often complicated and can result in much iteration as stakeholders such as independent testing laboratories and utility and industrial customers may have different interpretations of the requirements and its intended goals in regard to the performance of the individual components and cable system as a whole. This paper explores one approach of consolidating testing requirements per US standard AEIC CS9 for cable systems, ICEA requirements for cables and international standard IEC 60840 in single test program, in order to qualify cable, accessories and cable system at 150kV / 161kV level and 105 deg. C emergency operating temperature. Goal was to optimize testing protocol to capture all required tests and in the same time to customize test sequences in order to minimize lab time and eliminate unnecessary stressing of the cable system. The selection of the cable conductor size and electric stress levels at conductor and insulation screen was such that would maximize range of type approval and demonstrate robust performance margins, as this is often additional requirement by many customers and end users. Test program was performed in cable manufacturer’s factory laboratories and was witnessed, inspected and certified by independent HV testing laboratory. Testing loop consisted of 150kV XLPE cable with 2000 mm2 segmental copper conductor, two outdoor terminations (one with porcelain and one with composite insulator), two dry type GIS terminations in horizontal arrangement in SF6 housing and one single-piece premolded rubber joint. Big challenge was the fact that tests had to be performed at three different locations within the factory. The complete loop had to be moved 6 times between different laboratories with AC, PD, BIL and load cycling testing equipment and capabilities. In particular, this paper will present: Overview of relevant standards with respect to their level of harmonization and discussion on different requirements for components (cables and accessories) and system as a whole. Customized test program that combine all three required specifications: AEIC CS9-06, ICEA S-108-720-2012 and IEC 60840:2011. Design considerations for cable and accessories in regard to desired goals of the program. Testing approach “test as you build”, where set of initial tests are performed in each stage when new accessories are added to the loop, in order to mitigate the risk of installation errors. Design of special stands for cable accessories and SF6 housing to accommodate for movement of the whole loop between different testing locations. Design, planning and implementation of loop relocations. Results of the tests. Discussion on benefits of component approach - cable and cable accessories are designed and manufactured by different companies, each specializing in its area of expertise. JICABLE E15_0109.do oc Impro oved Method M of Unde erground d Cables s De etermining Ben nding Stiffnes ss of Janislaw w Tarnowski Institut d de recherche d’Hydro-Québec, 1800 B Blvd. Lionel Boulet, Varennes, Qué, C Canada J3X 1S1, tarnowskki.janislaw@ @ireq.ca The imp proved meth hod for determining the mechanicall bending prroperties of undergroun nd cables presente ed in this paper p is based on the e methodolo ogy describe ed by H.J. Jorgensen et al. in “Measurrement of th he rigidity of o polymeric cables” (Jiicable 2003), proposed as an inte ernational standard d. This metho od consists in i bending a cable progrressively by applying knoown displace ements at the mid-point betwee en two roller--type supporrts, and recording the corrresponding vertical force es at that location (Figure 1a). Fig. 1a C Cable bendin ng test Fig. 1b Cable displacement d t and corresponding bend ding force as a function oof time Displacement (mm) / Force (N) 700 0 Bending R Relaxation 600 0 500 0 F Force 400 0 300 0 200 0 Displac cement 100 0 0 0 2 4 6 8 10 12 14 16 18 20 Time (s) However, the analyttical models recommend ded by Jorge ensen et al. for the inteerpretation off the test results p provide only an a approximation, as the ey are based on a simplified first-ordeer equation. The T cable bending stiffness values v obtain ned in this manner arre underestimates and lead to an n unsafe assessm ment of asso ociated forces—for exam mple, the pulling forces or o the therm mo-mechanica al forces. Additiona ally, the test procedure described i n this public cation does not providee usable datta on the relaxatio on of the cable after bend ding. In order to improve the characte erization of ccable bendin ng properties s, the test pprotocol was modified and morre accurate analytical models have been develo oped for the interpretatioon of the tes st results. The revissed protocol features two o distinct ste ps for each test t (Figure 1b): 1 Bend ding: stiffnesss parameterrs of the cablle are assess sed Rela axation: relaxxation param meters are as sessed Each of these stepss requires its own analytiical model fo or data analy ysis and inteerpretation. Since S the cable is compressed d axially during bending g by the horizontal com mponent H oof reactions R at the supportss (Figure 1a)), the analytiical models w were develo oped based on o the seconnd-order equ uation for axially lo oaded beam ms. Additiona ally, the horrizontal force e H induces s a bending moment, calculated c relative tto the deform med position of the cable.. We have de emonstrated that this effeect, not acco ounted for in the firrst-order calcculation, incrreases the b ending stiffness modulus s EI by 15 too 30%, depe ending on the type of cable testted. The mod del for the re elaxation of the bending moment in the cable, ma aintained at a constant curvature, c is expresssed as an exponential curve, which h is depende ent on a single parametter characterrizing this relaxatio on over time. This parameter can be interpreted as a the time t for which tthe ratio of measured m momentss at time t and a at the beginning b of the relaxatio on stage is 1 e . A moree accurate relaxation r model w with two para ameters is also a propose d. The pape er describes the models developed and their application in experim mental determining of the e bending properties of underground cables. JICABLE15_0110.docx Integration of an 88 km 220kV AC Cable into the Victorian Electricity Network in Australia. Lee McMILLAN (1), Miron JANJIC (1), Ian CHRISTMAS (2) 1 - Beca Pty Ltd, Melbourne, Australia, lee.mcmillan@beca.com, miron.janjic@beca.com 2 - Beca Pty Ltd, Brisbane, Australia, ian.christmas@beca.com The Victorian desalination plant was commissioned in 2012 to provide a rainfall independent water supply for approximately 4 million people in Melbourne, Geelong and the surrounding areas. The plant is located near Wonthaggi 135 km southeast of the city of Melbourne. It treats seawater to potable standards using reverse osmosis technology. The plant has a production capacity of 150GLpa with the capability to expand to 200GLpa. The plant is capable of supplying approximately 30% of Melbourne’s water requirements. The plant is connected to the water and power networks via an 84 km transfer pipeline and an 88 km 220kV underground transmission line. The transfer pipeline and underground transmission line share the same easement for most of their length. The project also included a Booster Pump Station located approximately 75 km north of the plant The design considered overhead, underground, HVAC and HVDC options for the transmission line. Following stakeholder engagement, the end client requested a dedicated, HVAC, underground link. The 88 km, 220kV alternating current underground cable is the longest of its type in the world. The underground transmission line is designed to deliver 145MW to the desalination plant and 20MW to the Booster Pump Station. 500 mm2 Cu XLPE 3x 1C cable is used for the first section connecting the electricity network at Cranbourne Terminal Station to the Booster Pump Station. 400 mm2 Cu XLPE 3x 1C cable is used for the remaining sections to the plant. The cable system includes a 220kV shunt reactor station located approximately 38 km north of the plant. The development of the cable system included detailed studies in order to determine the design arrangement and equipment specifications necessary to meet the functional requirements and those associated with the network connection. The studies identified many requirements particularly related to long cable systems: Cable specification Reactive power compensation Capacitive switching and DC aspects associated with switching a fully compensated cable Resonance following switching and due to harmonics Earthing and electromagnetic interference This paper presents an overview of the cable system and the technical challenges that were overcome in its implementation. It provides a description of the various system components and the considerations that were used to define their specifications. JICABLE15_0111.doc Diagnosis of water tree in power cable based on loss current harmonic component energized by variable frequency resonance power source. Li ZHOU (1), Biao YAN (1), Jie CHEN (1), Fengbo TAO (1) 1 - Jiangsu Electric Power Company Research Institute, Nanjing, China, zl_jtt@163.com, fengchuiguolai@126.com, 2008840320@163.com, hvtaofb@163.com Water tree is the main form of an aging XLPE-insulated power cable, a kind of non-linear conductance properties can be detected in aging cables. Loss current contain harmonic component when insulation of cable excited by standard sinusoidal voltage. Detecting of loss current harmonic component is one of the best methods to assess the degree of aging cables. Feasibility of variable frequency resonance power source as an alternative exciting power source to diagnose and test aging cable is discussed in this paper, laboratory and field test results show that is entirely feasible, which can reduce the cost of diagnosis and testing greatly. JICABLE15_0112.docx North Auckland and Northland 220kV Cable Project Managing Thermo-Mechanical Forces in Large Conductor XLPE Cable Circuits Richard JOYCE (1), Ian Mc BURNEY (1) & Brian GREGORY (2) 1 - Transpower New Zealand Limited, 96 The Terrace, Wellington, New Zealand richard.joyce@transpower.co.nz & macbee@clear.net.nz 2 - Cable Consulting International, PO Box 1, Sevenoaks, Kent, TN14 7EN, UK brian.gregory@cableconsulting.net This paper describes the thermo-mechanical design aspects of the North Auckland and Northland (NAaN) 37 km long, 220kV cable project to provide security of supply to Auckland, the largest city in New Zealand. The city occupies a narrow isthmus between the Manukau Harbour on the Tasman Sea to the southwest and the Waitemata Harbour on the Pacific Ocean to the east. The cable route is geographically challenging as it passes between North and South Auckland, which are connected by the Auckland Harbour Bridge. The cable route comprises four sections of 220kV underground circuits of large conductor XLPE insulated cables that link existing and new substations. The project installation work commenced in 2005. Commissioning was completed in February 2014. The NAaN cable project will be of interest to utilities and cable designers worldwide as its route combines major section lengths of each type of thermo-mechanical installation design and the transition sections that connect them: 1. 16.4 circuit km of 2,500 mm2 cable installed semi-flexibly in unfilled ducts laid beneath a public transport busway. 2. 1.4 circuit km of 1,600 mm2 cable installed flexibly underneath Auckland Harbour Road Bridge. 3. 9.0 circuit km of 2,500 mm2 cable installed both flexibly and rigidly in a shared, ventilated cable tunnel underneath the Central Business District. 4. 9.0 circuit km of 2,500 mm2 of cable installed semi-flexibly in unfilled ducts, but including two cable bridges In view of the large conductor sizes, and the range of flexible and fixed installation methods, the transmission utility, Transpower, required that the thermo-mechanical forces generated by the cables be adequately evaluated and mitigated by sound installation engineering. The paper describes: 1. Engineering approaches taken to manage the thermo mechanical forces and movements, from the initial design phase through to final commissioning. 2. Techniques to measure the cable parameters, to FEA model the thermo-mechanical installations and to prove the installation designs. Key words: XLPE cables; Thermo-mechanical Forces; JICABLE15_0113.docx Indirect Pipe Water Cooling Study for a 220kV Underground XLPE Cable System in New Zealand Richard JOYCE (1), Simon LLOYD (2), Alan WILLIAMS (2) 1 - Transpower New Zealand Limited, 96 The Terrace, Wellington 6011, New Zealand richard.joyce@transpower.nz 2 - Cable Consulting International Ltd. PO.Box 1, Sevenoaks, Kent, TN14 7EN, UK simon.lloyd@cableconsulting.net & alan.williams@cableconsulting.net This paper describes the findings of a Proof of Concept Design Study for forced water cooling of the Brownhill - Pakuranga 220kV cable circuits installed on the Transpower NZ network. The study considered the use of separate pipe water cooling of 220kV power cables and accessories to increase the continuous current carrying capability of a new 220kV underground cable system. The 11 km double circuit connection was required to reinforce the Auckland grid and bring additional power into the Auckland area. The original design concept called for pipes to be installed with the building and commissioning of the cooling system approximately 20 years into their service life; during this phase of operation the study considered the potential to reduce the rating due to the need to limit the temperature of the empty plastic pipe so as to preserve its physical properties over this period. Further information was sought from other Wienstrom, Austria who had adopted a similar approach for a number of 380kV circuits commissioned in the 1970’s. Using generic cable and accessory designs, an arrangement of cooling stations (3 off) and cable loops (5 off) provided a force cooled current rating of up to 2632 A. The lack of an XLPE cable joint with a highly efficient water cooling design significantly restricted the water cooled rating downwards towards 2360 A to 2490 A. The paper discusses the factors of the joint design that will need to be considered in order to achieve a design capable of matching the rating of a water cooled XLPE insulated cable. The paper also presents the methods used and the considerations given to allow the cooling pipes to survive water pressures and temperature excursions over the expected life of the cable circuit in terrain having changes in elevation above 130 m. A description of the factors, affecting the decision of the system owner to select a naturally cooled 220kV underground cable circuit where the cables are buried directly rather than a water cooled option is also provided. The circuits have now been installed in New Zealand as part of the North Island Grid Update Project (NIGUP). Key words XLPE cables; Separate Pipe Water Cooling; JICABLE15_0114.doc Effect of Silicone Rubber's Electric Conductance Characteristic on Interface Charge Distribution inside XLPE Insulated HVDC Cable Termination Lewei ZHU, Boxue DU, Zhonglei LI School of Electrical Engineering and Automation, Tianjin University, Tianjin, China zhu.lewei@163.com; duboxue@tju.edu.cn; lizhonglei_tju@163.com Cross linked polyethylene (XLPE) cable terminations for high voltage direct current (HVDC) is of the potential of wide utilization because of their excellent advantages. However, interface charges accumulated between XLPE and silicone rubbers (SiR) in terminations enhance the field distortion, resulting in the reduction of cable reliability and lifetime. Temperature variation caused by heat generating from the current can influence the injection of charge, electric field and conductivity of XLPE and SiR. While, the electrical conductivity of XLPE and SiR is strongly affected by temperature and electric field strength, which at the same time affect the interface charge between XLPE and SiR. In this paper, we use pulsed electro-acoustic (PEA) method to study the interface charges accumulation within the termination, which has different SR as its reinforcement insulation, and analyze the influential mechanism of the insulating materials’ conductivity on the charge distribution. The results indicate that when the reinforcement insulation is made of common SiR, the interface charges accumulated are very large. However, when the SiR having a proper nonlinearly conductive property is deployed in the reinforcement insulation, the interface charge reduces significantly. It is concluded that the use of nonlinearly conductive SiR is an effective method to break the bottleneck in manufacturing XLPE HVDC cable termination. JICABLE15_0115.doc High voltage XPLE cable partial discharge localization technology based on high frequency signal transmission characteristics. Binwu WANG (1), Xueliang ZHU (1), Guangxin ZHAI (1), Wei WANG (2) 1 : Wuhan Talentum Electric Power CO., TLD, No.4 Huanglongshanbei Road, Wuhan City, Hubei Province, China. wangbinwu@yahoo.com, avx302@gmail.com, g.x.zhai@gmail.com 2 : State Grid Electric Power Research Institute. No.143 Luoyudong Road, Wuhan City, Hubei Province, China. wangwei3@sgepri.sgcc.com.cn This paper is based on high frequency signal transmission characteristics, analyzing partial discharge localization of high voltage cables. The existing testing technology of partial discharge is focused on the low frequency section (less than 100MHz). Because of the long distance of low frequency signal transmission, it is difficult to determining fault location. Due to the high frequency signal transmission distance is limited, and the attenuation of the signal, the location where the high frequency signal generated could be found. For verify the method used in partial discharge localization, a representative experiment has been done, the writer created a partial discharge point in the lab. Using the method of this paper, the fault location can be determined accurately, error in centimeters. Key words XPLE cables; Partial discharge; Electromagnetic wave; High frequency signal JICABLE15_0116.doc Study of 30 MHz to 1 GHz frequency signal transmission characteristics in high voltage XPLE cable. Binwu WANG (1), Xueliang ZHU (1), Guangxin ZHAI (1), Wei WANG (2) 1 - Wuhan Talentum Electric Power CO., TLD, No.4 Huanglongshanbei Road, Wuhan City, Hubei Province, China. wangbinwu@yahoo.com , avx302@gmail.com, g.x.zhai@gmail.com 2 - State Grid Electric Power Research Institute. No.143 Luoyudong Road, Wuhan City, Hubei Province, China. wangwei3@sgepri.sgcc.com.cn This paper is based on a model of electromagnetic wave transmission, analyzing transmission characteristics of electromagnetic wave in high voltage XPLE cables. The existing models and technology are all used in low frequency signal (less than 100 MHz), when used in high frequency section, there will be a large error. For using the model to high voltage cable well in the wide frequency band (30 MHz to 100 MHz), this paper creates a nonlinear physical model derived from the original attenuation model. To verify the deduction, a large number of experiments have been done, which using 110kV XPLE cable and HF signal generator. The result shows the new model improves the calculation accuracy of signal attenuation in high voltage XPLE cable of 11.2% in high frequency section. Key words XPLE cables; Transmission characteristics; Electromagnetic wave; Signal attenuation JICABLE15_0117.doc Design and implementation of a DTS system for 220kV cable temperature monitoring and fire detection in a 9.4 km tunnel David CHEN (1), Bob WILDASH (2) 1 - Transpower New Zealand Limited, Auckland, New Zealand, David.Chen@transpower.co.nz 2 - Wildash Consulting Limited, Paraparaumu, New Zealand, Bob.Wildash@transpower.co.nz Transpower New Zealand Limited has recently installed a number of 220kV cable circuits to reinforce the transmission system supplying the North of Auckland. The cable circuits are installed in a range of environments - direct buried, unfilled ducts, ventilated and unventilated cable trenches and tunnels with and without forced ventilation. All circuits are fitted with DTS systems. One circuit is installed in a 9.4 km long deep cable tunnel with forced ventilation. The cable tunnel is owned by another utility and already contained two 110kV cable circuits and in some sections several 33kV cables. Although the tunnel has been fitted with a sprinkler system for fire detection and extinguishing, it was considered desirable to provide an additional means of fire detection to allow the forced air ventilation system to be switched off as soon as possible after a fire is detected. To implement a simple and cost-effective fire detection system in the tunnel, Transpower opted using the DTS system designed for cable temperature measurement to perform fire detection, thereby eliminating the need to install dedicated fire detection hardware. This paper will outline the inherent conflict between accurate cable temperature measurement and fast fire detection within a single DTS system and explain how this was achieved by appropriate selection of measurement algorithm and post-processing of measured data. DTS systems can be difficult to integrate with utility SCADA system due to very little customisability of binary and analogue points. Transpower used a mixture of manufacturer’s built-in binary status and externally-set alarms on the Master station to report the system state and is therefore able to achieve an increased level of flexibility. The paper will provide details of DTS integration with Transpower’s SCADA system. Repeatable onsite calibration of DTS system is crucial in ensuring the designed level of accuracy is met for both temperature and spatial measurements. This paper will outline measures Transpower put in place during site testing and calibration. Finally, operational data to date for both cable temperature measurement and fire detection systems (if available) will be presented along with anomalies highlighted. This will include learnings to be taken into consideration for the detailed design of future cable circuits. JICABLE15_0118.doc The Completion of 275kV Suruga-Higashishimizu Line Tomoya OGAWA (1),Hiroshi SUYAMA (1),Shinichi KOBAYASHI (1) 1 - Chubu Electric Power Co.,Inc.,Nagoya,Japan,Tomoya, Ogawa@chuden.co.jp Suyama.Hiroshi@chuden.co.jp , Kobayashi.Shinichi2@chuden.co.jp 275kV Suruga-Higashishimizu line, which is composed of 3 km cable in total length, was completed in November 2013.We adopted 275kV XLPE cable with a copper wire screen and metallic shield inside a PVC jacket and applied 275kV Rubber Blocked Joint (RBJ) to the site for the first time in Japan. The tunnel to install 1000m long cables has an about 60 m high shaft and a rapid slope (angle 25%, distance 700 m). We established the method to place the cables in such a sever circumstance and checked its certainty by using a sample cable with the length of 180 m. The sample cable was pulled through the same route of the actual cables, and it was confirmed that the sample cable was intact as a result of the dissection and inspection. The quality management was considered important to apply 275kV RBJ, but there was no control criterion before. We created it by repeating the simulation tests with the sample products. To check the validity of the installed line including 275 RBJ, we conducted an AC electric examination, measuring the partial discharge. During the partial discharge measurement, we reduced the influence of the corona discharge to the outdoor sealing ends by shielding it electrically. JICABLE15_0119.docx Comparison of QuickfieldTM simulation of three single core XLPE cables, in flat formation, with complex loading, between not taking drying out and taking drying out of soil into account. BJ(Jo) LE ROUX, (1), JJ(Jerry) WALKER,(2) 1 - Vaal University of Technology, Vanderbijlpark, Gauteng, joleroux45@gmail.com. 2 - Visiting Professor, Vaal University of Technology, Vanderbijlpark, Gauteng, jerrywalker@walmet.co.za. Current rating calculations for power cables require a solution of the heat transfer equations which define a functional relationship between the conductor current and the temperature within the cable and its surroundings. The challenge in solving these equations analytically often stems from the difficulty of computing the temperature distribution in the soil surrounding the cable. An assumption is made to simplify thee computations, namely that the earth surface is an isotherm. The ambient temperature in summer will be taken as 25º C. The burial depth of the cables is in the order of 10 times their external diameter and for the usual temperature range reached by such cables this is a reasonable assumption, but for large cable diameters and cables located close to the ground surface a correction to the solution has to be used or numerical methods should be applied. Normally in such calculations the drying out of soil is not considered. This however, may have a very negative effect on the emergency rating of the cable. This paper will show the difference between taking drying out into account and when this is not taken into account. QuickfieldTM handles these types of computations with the greatest of ease. The main feature of this is to accurately model the cable and the surface. Each section of the cable must be drawn to scale and all the parameters of the constituent parts must be added. Once this is done all the boundaries and edge labels must be given the specific values. The next important part is the soil. The thermal conductivity changes with moisture content. The edges of the soil sample must be such that the temperature change due to the cable doesn’t affect the final boundary. The load curve is the next part that must be handled. Here a 24 hour load curve must be programmed. Once this has been done the simulation can start. The first part of the simulation was with a constant soil thermal conductivity. The second part was where the soil’s thermal conductivity changes as the soil is dried out. From the simulations it is quite obvious that when doing computations on cable ampacity and emergency ratings that drying out of soil is a very important factor that must be taken into account. Soil surface (isotherm) Burial depth d 2d 2d 3m Soil. 5m JICABLE15_0120.doc The study on the transient electric field distribution of HVDC cable Zhonghua LI, Lele LIU, Wenmin GUO, Yu CHEN (1) 1 - Harbin University of Science and Technology, State Key Laboratory Cultivation Base of Dielectrics Engineering, Ministry of Science and Technology, drzhhli@hrbust.edu.cn , liulele5186@163.com , g_wenmin@163.com , hustchenyu@163.com The conductivity is the main factor deciding the electrical field distribution in HVDC cable insulation, and the conductivity is sensitive the electric field and temperature. So the electrical field distribution in HVDC cable must dependence on the structure, applied voltage and temperature. Taking the typical structure of 320kV HVDC cable as an example, the steady state and transient electric field distributions under the different temperature gradients with different nonlinear properties of insulation were studied at 1.4 U0 and polarity reversal voltage with the software of COMSOL Multi-physics. The results showed that the insulation utilization coefficient is getting lower when the temperature gradient is getting higher,and that the transient insulation utilization coefficient at the process of polarity reversal voltage is significantly lower than the steady-state insulation utilization coefficient, here the insulation utilization coefficient is defined as the ratio of the average electric field and the maximum electric field. It is strongly recommended that the problem of transient electric field distribution must be considered seriously at HVCDC cable insulation materials research and insulation structure design. Key words: HVDC cable, Transient electric field, Temperature gradient, Insulation utilization coefficient JICABLE15_0121.doc Cables with smooth welded aluminum sheath. Bumyong JEOUNG, Jinwoo KIM, Byeongcheol MUN, Daeyoen KIM, Youngjun.KIM, Kyongtae LEE, Jungsik KIM 1 : ILJIN Electric, 112-88, Annyoung-Dong, Hwasung-Si, Kyunggi-Do, 445-380, Korea, bumyong.jeoung@iljin.co.kr Most HV cable systems are custom designed to suit also the specific environmental parameters and operating requirements of a particular route and loading conditions. The metallic sheath plays a key role in the design of High Voltage underground cable systems, as it must satisfy essential electrical and mechanical functions to ensure the correct operation of a cable. Cables with lead alloy sheath provide all necessary guarantees in terms of technical characteristics. However, the main disadvantages of cables with a lead alloy sheath are weight. On the other hand, cables with corrugated aluminum sheath have a significantly reduced weight when compared with cables having a lead alloy sheath. But, it have the disadvantages of not only a lower transmission capacity, due to the presence of an air gap under the corrugations. Also a larger diameter and accordingly shoter delivery lengths. Because of that, we developed and manufacture the mass of cables having smooth welded aluminum sheath. It is minimized their disadvantages, resulting in a cable with lighter weight, reduced diameter and bending radius with a comparative longer length. Also guarantees excellent electrical and mechanical performance, full fluid tightness and compliance with even the strictest environmental requirements. The smooth welded aluminum sheath consists of an aluminum tape, longitudinally applied over the cable core, shaped around it and welded. The application and welding of the aluminum tape, and the extrusion of the plyethylene are carried out through a special process on the same line, which undergoes continuouis video recorded inspection ensuring effective quality control. Extensive tests have proven that the water tightness and resistance to corrosion of the smooth welded aluminum sheath cable meets the most stringent standars. Depending on the short circuit requirements, the welded aluminum sheath can be complemented with copper wires. The ILJIN Electric is characterised by a competent and experienced approach to turnky total solution. We have always a guarantee for the supply of products and services based on quality standards. JICABLE15_0122.doc Research on error control of optimal computation combining temperature field with ampacity of cables under complicated conditions. Shan JIANG (1),Yin LI (1), Xueliang ZHU (1), Guangxin ZHAI (1),Wei WANG (2) 1 - Wuhan Talentum Electric Power CO., TLD, No.4 Huanglongshanbei Road, Wuhan City, Hubei Province, China. shnshw@yahoo.com, Jackli_dlut@yahoo.com, avx302@gmail.com, g.x.zhai@gmail.com 2 - State Grid Electric Power Research Institute. No.143 Luoyudong Road, Wuhan City, Hubei Province, China. wangwei3@sgepri.sgcc.com.cn There are many factors affecting the cable ampacity. The error will be large when calculating the ampacity of cables in multi loop cable cluster laying according to the traditional method. For this reason, this research, based on the knowledge of heat transfer, compute the cable temperature field, structures heat conduction equation and boundary condition, and applys optimal numerical computation of temperature field and ampacity of cables under complicated conditions. It uses the finite element method to compute temperature field outside the cables and the cable surface temperature and uses temperature formula to derive the ampacity of cables. Then, it effectively avoid the theoretical model’s defect that it cannot compute temperature field outside the cables exactly. This method combines the finite element method with theoretical model and controls the error from an integrated viewpoint. In comparison with the traditional method, it shows that the error is controlled within 3.1%. Key words Cables ampacity; Complicated conditions;Finite element;Theoretical model;Error control JICABLE15_0123.docx Determination of fire behavior of polymer cable materials and mathematical modeling of highly-filled halogen-free compound burning Mikhail SHUVALOV (1), Mikhail KAMENSKIY (1), Aleksandr KRYUCHKOV (1), Tatiana STEPANOVA (1), Andrey FRIK (1), Dmitry SAVIN (1) 1 - VNIIKP, Moscow, Russia, shuvalov@vniikp.ru Due to adverse combination of combustible cable polymer materials and ignition sources occurring under emergency operation conditions the cables become fire-hazardous objects. Moreover, taking into consideration that branched cable grids are not only bearers of fire risks but also channels along which fire can propagate in buildings and constructions, the improvement of cable fire safety characteristics is important problem at present. The required level of fire safety of cable products is achieved mainly by using special highly-filled polymer materials. The behavior of a cable exposed to fire is determined by the material characteristics which have to be measured under controlled conditions simulating the effect of external thermal flow and flame and similar to the conditions of cable burning in fire. Such conditions are simulated while testing materials in a Cone Calorimeter. This instrument is used to measure the entire set of fire characteristics of a material, as well as to register the dynamic variations of measured parameters. A comparative study of the fire parameters was carried out on a number of halogen-free materials that are used in fire performance cable constructions intended for various applications. The recommendations for choosing proper compounds to make insulation, filling and sheath and to design flame retardant cables are based on the results of the performed analysis. The study results suggest that in designing cables, particularly cables insulated with cross-linked polyethylene which is the most combustible insulating material, it is essential to select filling and sheathing materials that have the lowest peak values of heat release rate and the longest periods of time it takes for these peak values to be achieved. Critical ratios of these values to ensure the compliance with the flame retardancy requirements for cable laid in bunches were revealed. The adequacy of the suggested approach to the selection of polymer materials at the stage of cable design is proved by the cable specimen test results. A mathematical model was developed for the physical and chemical processes going on in a non charing halogen-free polymer material under exposure to flame. The model makes allowance for the transient heating of the material and the thermal decomposition of its basic components which is accompanied by a reduction of mass and thickness of the polymer part of the specimen. Thermal analysis methods were used for experimental determination of the thermal decomposition kinetic parameters of halogen-free polymer materials (activation energy, rate constant for different stages of pyrolysis, thermal effect, etc.) which are required for mathematical modeling. The simulation results are in satisfactory agreement with the cone-calorimetric experiments data. The described approach to the mathematical modeling of the burning processes of halogen-free materials can be further used to investigate the combustion behavior of flame retardant cable products. JICABLE15_0124.doc Design and Analysis of High Current Heat Cycles Test Set for Underground Cable Att PHAYOMHOM (1) 1 - Metropolitan Electricity Authority (MEA), Thailand, att_powermea@hotmail.com The Heat cycles test set is the test equipment used for cables quality evaluation as required by several standards that equipment should be tested to ascertain that it is free from abnormality prior to the actual operation, especially, when the equipment is subjected to temperature change in cyclic manner. Heat cycle feeds current into the tested cable until heat is built up and then stop the feeding current. The cable will let cool itself down naturally in the set time period. The above mentioned action will be repeated in a number of cycles as required by the standard. The cable sample undergone the test will then be subjected to quality evaluation and shall still comply with all the requirements required by the standard. In order to develop a highly reliable and efficient heat cycles test set that can satisfy the requirement of the standard. The heat cycle test is then desired to possess the following characteristic and ability : 1) Two sets of separate current controller that can be used to control the resulted temperature during on-cycle automatically. 2) Digital data recorder with 6 inputs (extendable to 12) to accommodate as many as temperature and other sensors, communicable via RS232 and RS485. The recorder can upload its contents to flash memory card, have 2 to12 digital outputs for alarms, and a 5.5 inch LCD monitor. 3) Number of cycles and time period can be set. 4) Feedback controllable using constant current or temperature. 5) Fuzzy logic used in regulating current and temperature. 6) two selectable operation modes: manual and computer control. The heat cycles test set under the above mentioned design is believed to have high reliable result and cost effective when compares with the costly foreign product. The heat cycles test set is designed and built in accordance with what is discussed in the article for high voltage cables testing. The test set feeds current periodically into the cable under testing. In oncycle, the test set heats up the cable for at least 8 hours while in the off-cycle, it allows the cable to cool down for at least 16 hours until its conductor temperature is within 10°C above the ambient temperature. The current that is fed into the cable during the on-cycle is to be recorded for 2 consecutive hours when the conductor temperature remains constant as per the insulation standard (IEC 60840-2004). The heat cycles test set has two separate current sources, which can be used independently. Programmable Logic Control (PLC) is used in controlling the operations of the test set, e.g. the two current sources can be programmed to work together, moreover, the number of testing cycles, feeding current, and also the resulted temperature of any on-cycle can be selected. In conclusion, the test set built as described, can perform its functions satisfyingly while accomplishing cost reduction. This is because an imported test set of the same kind is more expensive. Besides, a digital recorder is installed for recording temperature and current during testing. An acceptable error of 1.45% to -1.62% of the test set is obtained when undergone the calibration. Key words Cable, Calibration, Heat cycles test set, Programmable Logic Control (PLC), Thermocouple JICABLE15_0125.doc Challenges with the 2x100 km 132kV AC Submarine Cable project Ras Laffan to Halul Johannes KAUMANNS (1), J P KIM (2), J B PARK (3),Frank de Wild (4), Kees-Jan van Oeveren (5) 1 - LS Cable&System Ltd., Donghae, South Korea, jkaumanns@lscns.com 2 - LS Cable&System Ltd., Gumi, South Korea, jp0301@lscns.com 3 - LS Cable&System Ltd., Doha, Qatar, jbpark1@lscns.com 4 - DNV GL, Arnhem, The Netherlands, Frank.deWild@dnvgl.com 5 - DNV GL, Singapore, KeesJan.vanOeveren@dnvgl.com Qatar Petroleum (QP) intends to upgrade the electrical power supply to meet the future additional power requirements for Halul Island with forecasted electrical power shortfall starting from year 2011. LS Cable & System Ltd. (LSC) was awarded by QP the EPIC project which will provide power supply to Halul Island from Kahramaa electrical network at Ras Laffan through 2 numbers of 132kV submarine 3-core XLPE cables with a capacity of 100MW each to meet the present and future electrical power demand of Halul Island. This paper describes the challenges for this large scale submarine cable project: The qualification, quality, and testing procedures covering all stages of the project, from production (routine and sample tests), type tests, laying tests up to the final laying and commissioning procedures. The general qualification procedures for this project are based on Cigre TB490 recommendations but additional project related tests and qualification were necessary. The total testing and qualification procedure was closely discussed with the independent surveying party DNV-GL (former DNV-KEMA) and agreed between all parties involved. By the various specially defined test procedures and manufacturing processes, the quality of the power cable could be assured up to a very high level, and has led to full verification and certification according to ISO 10474 / EN 10204 by DNV GL. Modern, state of the art production facilities in Donghae, South Korea, allows production of the needed individual shipping length of 50 km with a weight of 3.800 t. As located direct at the harbor, world-wide shipment of long length submarine cables with an individual cable weight up to 10.000 t is possible for the factory. All four delivery lengths with a total weight of more than 15.000t have been manufactured in 2013/2014 and were shipped in time to reach their final destination in the Persian Gulf in front of Qatar. The laying and off-shore jointing procedures are ongoing and commissioning tests are planned for early 2015. The required factory joints for the XLPE insulated cable have been made by tape-molding technique under controlled clean room conditions to guarantee the required high quality of the product. A detailed deduction on how quality can be built-into the manufacturing procedures, and additional tensile strength and X-Ray checks, for example, confirm the failure free result of the works. Sample tests have been carried out at each extrusion length and on factory joints direct taken from production to demonstrate the continuous high level of the quality during the total production time. All the relevant routine tests, sample tests, type tests and additional qualification tests have been witnessed continuously and approved by DNV-GL as independent surveyor. For example, the deployment procedure for the off-shore field joint (OFJ) was analyzed in detail: A practical sea trial simulation test has been carried out with full size cable and joint to demonstrate the functionality of the offshore field joint under all laying conditions. By analyzing the forces and movements in detail during the deployment procedure at the vessel, a thorough test was performed, executed on land, to ensure that the submarine cable and the OFJ are well installable aboard a ship, meeting the required quality levels. The intensive testing and qualification activities as applied in this project are reducing the overall risks for such large scale projects to the benefit of all involved parties. The paper will therefore focus on how these benefits have been obtained in this large submarine cable project. JICABLE15_0126.docx Application of knowledge engineering approach to mitigate the infant mortalityrisk of HV cable system in MEA Thailand Asawin RAJAKROM (1) 1 - 1192 Rama 4 road, Klongtoey, Bangkok, Thailand, asawinraja@mea.or.th Metropolitan Electricity Authority (MEA), the distribution utility supplying electricity to the customers in Bangkok Metropolis, Thailand, has implemented the underground cable system for several decades. The main purpose is to enhance the distribution system reliability and beatify the Bangkok metropolitan cityscape. Recently, MEA has launched the roadmap tosupportthe government policy in turning Bangkok Metropolis into the capital of ASEAN through the modernization its distribution network. Hence the number of undergrounding projects has been established for the near future. The projects include the conversion of overhead to underground system along the main streets in Bangkok totaling 260 km of street length as well as the strengthening of sub-transmission system totaling 270 circuit- km. This passes on the huge burden to the project execution team. MEA installation team although possesses very high skill through lifelong experience in cable jointing works, working under the adverse environment and stressful condition somehow deteriorates the quality of jointing work. It was evidenced by the number of accessories breakdowns during the commissioning soak test on the cable line, particularly the cable joints which installed in the manhole buried underneath the road surface. It sometimes even occurred right after the voltage switching-on. This event can be considered as “infant mortality” of bathtub failure pattern that seriously required particular attention from the project execution team. The knowledge engineering approach together with the analytical tool has then been employed to digest the problems, analyze causes and effects and seek for the appropriate solutions. Knowledge engineering provides the methods to obtain a thorough understanding of the structures and processes used by knowledge workers (or cable jointers), even where much of their knowledge is tacit, leading to a better integration of information technology in support of knowledge work. On the other hand, knowledge engineering is a process of eliciting, structuring, formalizing, and operationalizing information and knowledge involved in a knowledge-intensive problem domain (or cable jointing works), in order to construct a program that can perform a difficult task adequately. By employing the knowledge engineering methodology, it is found that several factors could contribute the joint failures. The problems include: the cable joint that may not be designed to fit the installation environment, the jointers, although possessing high skill in usual jointing works, that may not be well trained for particular installation, the uncontrollable site installation conditions, the times duration allowed to carry out the jointing job too short, the inappropriateness of cable testing methods, the switching procedure to energize the cables, etc. As a consequence, the countermeasures have then been developed to overcome the problems of joint failure including the system design review, the acquisition of proper installation and testing tools, and especially the adequate training for the jointers. This paper aims to share the experiences of applying knowledge engineering approach to mitigate the infant mortality risk of HV cable system in MEA. Key words Cable joint failure; Cause effect analysis; HV cables; Infant mortality; Knowledge engineering JICABLE E15_0127.do ocx Meas suremen nt and modelin m ng of su urface charge a accumulation on insulators s in HVD DC gas insulate ed line (GIL) Boya ZH HANG (1), Qiiang WANG (1), Guixin Z ZHANG (1) 1 - Tsing ghua Universsity, Beijing, China, C zhang gby13@maills.tsinghua.e edu.cn, wqtsi nghua@163 3.com, guixin n@mail.tsing ghua.edu.cn The devvelopment off electrical trransmission systems all over the wo orld will invo lve the insta allation of eographical distance between eneergy genera HVDC ssystems to bridge the growing ge ation and consump ption. Furthe er, the conne ection of new w renewables s such as offfshore wind farms to the e grid has to be do one with DC technology as long as A AC sea cables are not possible. Altternative to overhead o lines, ga as insulated line l (GIL) is an a optimum technology for f bulk electric power traansmission at a high or ultrahigh h voltage and d can be insttalled underg ground or in tunnels with low environnmental impa act, which makes th his technolog gy interesting g for the futu re. However, DC voltage causes ma any problem s in dielectric stability of the insulatinng system. Unlike U the quasi-sta atic displace ement field under AC vvoltage whic ch is determ mined by thhe permittivitty of the insulating materials and the giv ven electrod de arrangem ment, the sta ationary resisstive field under u DC voltage iis dominated d by the volu ume and surrface conduc ctivity of the insulating m materials. The e surface charges will accumu ulate particullarly at the i nterfaces be etween differrent materialls and thus influence the diele ectric stress of the insula ation system m significantly y. Especially in situationss of polarity reversal, the flash hover voltage can be re educed conssiderably in the presenc ce of accum mulated charges. The mechaniism of surfacce charge ac ccumulation has not yet been fully un nderstood. T Therefore, the e surface charge p phenomenon n on the insullators in GIL has to be re evisited for fu uture HVDC aapplications. For this purpose, a surface s charrge measure ement system m is established using thhe electrosta atic probe method based on a 220kV 2 GIL unit. The surfface charge distributions d on a cone-tyype insulatorr made of Al2O3 fillled epoxy re esin are obttained underr different vo oltage duration, voltage polarity and d voltage amplitud des. Some ph henomena is s studied in th his paper and the possible sources oof surface cha arges are discusse ed. Meanwh hile, a simula ation model is used to ccalculate the surface cha arge accumuulation and stationary s field disttribution on th he gas-solid interface of the insulatorr in the GIL unit u under DC C voltage. The model takes intto account bo oth the dielectric propertties of the ins sulator material and physsical process ses in the surround ding gas inclu uding the charge carrierss’ generation n, drifting, rec combination aand diffusion n. With this paper, the authors would w like to o contribute a better understandingg of surface e charge esults in this paper may be useful accumullation phenomenon and its mechanissm in HVDC GIL. The re ptimization of HVDC gas insulated sy ystem. for the design and op e: Distribution n of surface potential on the GIL insu ulator under negative n DC voltage Example JICABLE15_0128.docx Development of a 500kV PPLP MI cable system for HVDC applications Eui-hwan JUNG (1), Sung-yun KIM (1), Byung-ha CHAE (1), Hyun-sung Yoon (1), Chae-hong KANG (1), Su-kil Lee (1), Seung-ik JEON (1) 1 - LS Cable&System, Gu-mi, Korea, sikemaro@lscns.com , sykim13@lscns.com , bhchae@lscns.com , yoon1216@lscns.com , chkang@lscns.com , sglee@lscns.com , sijeon@lscns.com This paper describes the development of the 500kV DC Polypropylene Laminated Paper (PPLP) mass-impregnated type cable system for HVDC transmission lines. As you know, mass-impregnated type cable generally has only insulating layer with the kraft paper impregnated with a high-viscosity insulating compound. But, Polypropylene Laminated Paper is made of a layer of extruded polypropylene (PP) film sandwiched between two layers of kraft paper. Thanks to PP film and its combination with kraft paper, PPLP has higher AC, impulse (Imp.) and DC breakdown (BD) strengths as well as lower dielectric loss than conventional kraft paper insulation. In addition, Kraft MI cable has a limitation for the maximum conductor temperature as 55 . But this PPLP MI cable has higher maximum conductor temperature than that of kraft MI cable due to advantage of oil drainage characteristics. It is the most economic type of cable for HVDC transmission. LS cable&system already developed ±250kV mass-impregnated type kraft cable system with crosssection of 900 mm2 conductor, flexible joints and out-door terminations. This submarine cable system was successfully established between Jindo and Jeju Island in Korea. In this paper, DC 500kV PPLP MI cable system was developed including land joints, flexible joints and outdoor-terminations. In order to prove the mechanical and electrical performances, the type test was carried out according to CIGRE recommendations. A full scale cable system has been tested successfully. And additional load cycle and polarity reversal tests on the cable system showed a higher performance compared with a similar mass impregnated paper cable. Key words HVDC transmission; Submarine cable; DC Polypropylene laminated paper; Land joint; Outdoor termination JICABLE15_0129.doc Design and manufacturing of ±200kV HVDC submarine power cable in Zhoushan flexible dc transmission project Ming Hu (1), Shuhong Xie (1), Jianmin zhang (1) 1 - Zhongtian Technology Submarine Cable Co., Ltd, Nantong(China), hum@chinaztt.com , xiesh@chinaztt.com, zhangjm@chinaztt.com Zhoushan multiterminal flexible DC transmission project in Zhejiang province, China is the world’s first five-terminal DC transmission project, in which 103 km ±200kV submarine fiber optic composite power cable linking Dinghai and Daishan is supplied by ZTT transmitting capacity of 400 MVA with conductor cross section of 1000 mm2. This paper demonstrates the simulation verification design of the insulation thickness and electric stress of the ±200kV HVDC cables for this project and proves that the electric stress at any point of insulation complies with the performance of insulation material. Manufacturing process of cable and factory splice is also introduced together with the relevant tests carried on the submarine composite cable including DC voltage test according to CIGRE TB 496 and mechanical test that verifies the reliability of the power cable factory splice and optical fibers. JICABLE15_0130.doc Investigation of electrical and morphological properties of 10kV XLPE cable insulation specimens Mikhail SHUVALOV (1), Vladimir OVSIENKO (1), Mikko LAHTI (2), Pekka HUOTARI (2) 1 - JSC “VNIIKP”, Shosse Entuziastov, 5, Moscow, Russia, 111024, shuvalov@vniikp.ru , vovsienko@vniikp.ru 2 - Maillefer Extrusion Oy, Ensimmäinen Savu, 01510 Vantaa, Finland, mikko.Lahti@maillefer.net , pekka.huotari@maillefer.net Nowadays cable and wire manufacturers and consumers are interested in the development of new test methods and search of additional criteria for product quality assessment. The paper presents the investigation results for the specimens of commercially produced 10kV XLPE cables fabricated (using manufacturing technology) at different plants, under different production conditions but on similar equipment with the use of the same materials. The investigation involved the analyses of the following: the morphology peculiarities (specimen structure) by optical and thermal methods, the insulation system defect rate (the number of thermally modified polyethylene particle inclusions in the insulation and semiconducting screen protrusions), the insulation resistance to electrical tree origination and growth. The electrical tests were conducted on specimens with inserted calibrated defects. The test setup allowed monitoring under high voltage and with high optical resolution of the process of electrical tree origination and development. The investigation results indicate that the minimum defect rate of the insulation system was observed in the specimens fabricated at minimal/moderate extrusion speeds, and the maximum polyethylene insulation resistance to electrical tree origination and development was observed in the specimens with a lower melting temperature (lower degree of crystallinity). The investigations demonstrated that lower values of the crystallinity degree refer to the specimens with smaller embryonic spherulites. Key words Electrical insulation; Cross-linked polyethylene (XLPE); Thermal analysis; Optical microscopy; Electrical tree JICABLE15_0131.doc Research and Development of ±320kV Flexible HVDC Power Cable Ming HU (1), Shuhong XIE (1) Xiaowei WU (1) 1 - Zhongtian Technology Submarine Cable Co., Ltd, Nantong(China), hum@chinaztt.com , xiesh@chinaztt.com , simon.wu@zttcable.com HVDC power cable is one of the most important equipments in the flexible DC transmission project. ZTT developed the ±320kV XLPE insulated HVDC power cable according to the actual demand of the ±320kV flexible DC transmission project in Xiamen city, China and the cable had already passed the type tests by TICW and EETC. This paper introduces the development of ±320kV HVDC power cable focusing on the test of space charge and electrical conductivity characteristic of insulation and screen material of DC power cable for the insulation design. Also the way of achieving longitudinal water tightness for stranded circular conductor with cross section of 1800 mm2 is analyzed as well as subsequent cross-linking and degassfication process of insulation. Besides, the type test of the ±320kV XLPE insulated power cable is introduced by describing the test method and procedure of electrical performance of cable system. ±320kV HVDC power cable is independently researched and developed in China and its industrialization has just started and will serve domestic and overseas flexible DC transmission projects. JICABLE15_0132.doc Testing the Allowable Compressive Limit of HVAC Submarine Cables Ahmed M. REDA (1,2), Alex Kwang Hwan OH (3), Peter VAN DER WIELEN (4), Gareth L. FORBES (2) 1 - Qatar Petroleum, Doha, Qatar, reda@qp.com.qa 2 - Department of Mechanical Engineering, Curtin University, WA, Perth, Australia, Gareth.Forbes@curtin.edu.au 3 - LS Cable & System Ltd, Seoul, South Korea, khoh@lscns.com 4 - DNV GL - Energy, Arnhem, The Netherlands, peter.vanderwielen@dnvgl.com Submarine cable crossings are a common feature of offshore hydrocarbons field development and crossing numbers inevitably increase with development density. Cable crossings add cost to a new submarine cable system and should be obviated where possible, but not at the expense of increasing the cable length uneconomically. It is often a requirement to maintain a positive separation between the crossing cable and the crossed assets. The common concept for a submarine cable crossing is to raise and support the new cable up and over the existing pipeline / cable / umbilical. The support is preinstalled on the seafloor and the new cable is laid over the support. Common support concepts include pre-cast concrete mattresses and sleepers and grout in-situ fabric formwork. In a recent project in the Arabian Gulf the positive vertical separation, between the crossing subsea cable and crossed assets, is achieved via the use of articulated padding. The articulated padding is lightweight and installed around the cable which comprises of two polyurethane half shells attached via corrosion resistance alloy banding. The entire length of the subsea cable is post-trenched, for the protection of the subsea cable, except at the crossing locations. As such, the subsea cable is installed with low touchdown tensions in order to enable the post-trenching operations. The location of the crossing is associated with strong currents with 1 year return surface currents reaching 2.5 knots. The results from the installation analyses highlighted several potential issues with the articulated padding and indicated that the bare cable experiences high compression loads at the touchdown point which were outside the allowable design criteria of typical submarine cables. Therefore, a project specific test program is undertaken to determine the allowable axial compression limit of the 10-inch HVAC submarine cable. This program included both pure axial compression tests and bended compression tests, in order to mimic the installation conditions as good as possible. The industry standards and recommended practices are still silent regarding this new test arrangement, which could be adopted in order to determine the allowable compression data. JICABLE15_0132.doc This paper describes a new test arrangement, which can be used in the future projects to determine the allowable compression data for a submarine cable. Keywords: Submarine Cable; HVAC; Submarine Cable Installation; Crossing Design; Allowable Axial Compression; Cable Bending; Recommended Test JICABLE15_0133.doc Development of 500kV XLPE cable accessories Guoji LI (1), Kenji TAKAHASHI (1), Tsutomu SUMIMOTO (2), Zhaojian LIU (3), Akihisa KUWAKI (4) 1 - SWCC SHOWA Cable Systems Co., LTD. Sagamihara City, Kanagawa Province, Japan, k.ri071@cs.swcc.co.jp , k.takahashi372@cs.swcc.co.jp 2 - SHOWA-TBEA (Shandong) Cable Accessories CO., LTD. Xintai City, Shandong Province, China, t.sumimoto583@cs.swcc.co.jp 3 - TBEA Shandong Luneng Taishan Cable CO., LTD. Xintai City, Shandong Province, China, lzj8003@126.com 4 - EXSYM Corporation, Sagamihara City, Kanagawa Province, Japan, akihisa_kuwaki@exsym.co.jp XLPE cable accessories for 500kV underground power transmission lines are developed, and have undergone type test and prequalification test in accordance with IEC62067, at Wuhan High Voltage Research Institute (WHVRI, China) known as the reputable impedance third party certification authority. The certificate has been issued from WHVRI upon successful completion of the tests. The developed cable accessories consist of straight through joint, outdoor sealing end and GIS sealing end. A Rubber Block insulated type Joint (RBJ), which the main insulation component is made of cold shrinkable rubber, is developed as the straight through joint for 500kV XLPE cable. The factory expansion technology is developed and applied, because it allows reduction of construction times due to its skill-less assembly processes. Moreover, the outdoor sealing end was developed which consist of a rubber stress relief cone with the application of the factory expansion technology, porcelain bushing or composite bushing with heavy pollution level, and liquid insulating compound. The GIS sealing end was developed with a traditional prefabricated structure, an epoxy bushing, a rubber stress relief cone and a springs device for rubber stress relief cone. This paper describes the specifications and the test results of the developed cable accessories. KEYWORDS 500kV, XLPE cable accessory, pre-moulded one piece joint, factory expansion technology JICABLE E15_0134.do ocx The space charge charac cteristic c in DC C-XLPE cable after 400kV V PQ tes st. Tomohikko KATAYAM MA(1), Takanori YAMAZ ZAKI(1), Yoshinao MURA ATA(1), Shoj i MASHIO(1), Tsuyo oshi IGI(1), Naohiro N HOZ ZUMI(2), Massahiko HORI(2) 1 - J-Pow wer Systemss Corporation n, 5-1-1 Hitakka-cho Hitac chi-shi Ibarak ki-ken 319-14414, JAPANA A, katayyama.tomohiko@jpowers s.co.jp (Tomo ohiko Kataya ama), yamazaki.takanori@ @jpowers.co o.jp (Taka anori Yamazaki), murata..yoshinao@j powers.co.jp p (Yoshinao Murata), masshio@jpowe ers.co.jp (Shojji Mashio), ig gi.tsuyoshi@jjpowers.co.jp p (Tsuyoshi Igi) 2 - Toyohashi Univerrsity of Techn nology, 1-1 H Hibarigaoka Tenpaku-cho o Toyohashi--shi, Aichi-ke en 4418580, Japan, hozzumi@icceed d.tut.ac.jp (Na aohiro Hozumi)), m11120 03@edu.tut.aac.jp (Masah hiko Hori) In recen nt years, hiigh voltage DC (HVDC C) cross-link ked polyethy ylene powerr cables ha ave been develope ed and alrea ady been put into practiccal use. CIG GRE TB 496 (former 2199) is predominant test protocolss in order to o perform a long l term prre-qualificatio on (PQ) test and type teest. J-Power Systems has alrea ady successfully conductted a 400kV type test and a PQ test in accordancce with CIGR RE TB496 on the ccomplete cab ble system with w accesso ries, under the t polarity reversal r condditions as re eported in Jicable 2 2013 and hig ghlighted in Fig F 1 and Fig g 2 below. In the meantime, the ere are some e technical d discussions in n users/manufacturers/teechnical com mmittee of internatio onal standarrds if space change c accu umulation wo ould affect the deterioratioon of cable insulation i in DC u use and the erefore residual space change me easurement might be uuseful to check the performa ance of DC-X XLPE insulattion as well a as cable des sign. On the other hand, CIGRE 490 does not require a any measure ement of space charge in n insulation. Authors have many experiences s in the mea asurement of o space cha ange in cablee insulation material. Space charge measu urement, one e of the eval uation metho ods, is a sim mple way to aanalyze spac ce charge behaviorr, electric fie eld distortion n and space e charge dis stribution in the insulatoor. In general HVDC cables rrequire low accumulation a n of space charge, unifform electric fields and long-term sttability of space ch harge distribu ution. To me easure space e charge, pulsed electroa acoustic (PEA A) method is applied. In this paper, we describe the re esult of spacce charge measurement using PEA m method on a full-size HVDC cable sample after the 400kV PQ testt in order to attempt a to ev valuate any cchange or increase of space ch hange accum mulation by polarity p reverrsal operation n after a long g term test. V PQ test Fig. 1 View of 400kV Fig. 2 Layout of 400kV 4 PQ teest JICABLE15_0135.docx Partial Discharge Measurements in the Sub-VLF-Range Prof. Kay RETHMEIER(1), Rudolf BLANK(2) 1 - Kiel University of Applied Sciences, Kiel, Germany, kay.rethmeier@fh-kiel.de 2 - b2 electronic GmbH, Klaus, Austria Testing high voltage cable systems on-site is often limited by the demand of reactive power. Reducing the test frequency can solve this problem. Therefore, VLF cable testing is already implemented in several international standards. The significantly reduced test frequency, often 0.1 Hz compared to 50 Hz and 60 Hz, respectively, is often considered by increased test voltage levels in order to compensate differences in the physical mechanism of the insulation’s breakthrough process. If the withstand voltage tests are combined with diagnostic PD measurements, also the relevant PD parameters, as PDIV, PDEV and apparent charge have to be challenged with respect to their comparability to power frequency. Many studies have been published in the past, evaluating this topic in detail. Nowadays, with further increasing cable length, and with the need to use small and lightweight test equipment for off-shore applications, even the reduction of the test frequency down to 0.1 Hz is often not sufficient to provide the reactive power for the test object. Therefore, most commercial test kits provide test frequencies below 0.1 Hz (as 0,01 Hz = 10 mHz), still in accordance to the standard IEC 60060, where VLF voltage is defined as an alternating voltage with up to 1 Hz. As a consequence, the PD behavior of the test object may also be influenced as well. This contribution presents the results of systematic test sequences with sinusoidal voltage, using 50 Hz, 0.1Hz, 0.05 Hz, 0.02 Hz and 0.01 Hz. Besides parameters as PDIV, PDEV and q, also phase resolved PD patterns (PRPD) were generated and compared. JICABLE15_0136.docx A Rodent’s dilemma: To chew a cable or not to! Ms. Varsha POTE (1), Assistant Technical Marketing Manager 1 - C Tech Corporation India varsha.pote@ctechcorporation.com Rodents are wily creatures; though small they can do unthinkable damage to our cables! Rodent menace is experienced by people from all walks of life. The rich, the poor, the mighty and the weak all are affected the same. Their affinity to chew the insulation of the cables poses a great threat to the cables in all sectors. Telecommunication sector, which is said to be the backbone of the business world, has been plagued with rodent problems for a very long time now. Companies are losing millions on a daily basis due to power outages caused by rats, squirrels and the likes. It has been reported that everyday at least one power outage is caused due to these pesky creatures called rodents. Rodents can inflict heavy damage in the automobile sector too. Cables in all applications are vulnerable to rodent damage be it in your home or your office. Heavy monetary losses are incurred because of rodents damaging the cables. Not only cables, all the polymeric applications like water pipes, gas pipes, polymeric films are susceptible to rodent damage. Along with rodents; there are other pests who cause trouble in our paradise. Cables are also vulnerable to termite and ant attack. Termites and ants secrete formic acid which dissolves most of the polymers and causes damage to the applications. Subterranean termites pose a major threat to underground cables. Conventional chemicals are used to deal with these vile pests, which are toxic and hazardous. These chemicals have now become ineffective and inefficient as most of the target species have developed resistance to these chemicals. Also, these hazardous chemicals harm both target as well as beneficial non-target species. We at C Tech Corporation have formulated products which are in the form of polymer-specific masterbatches to combat the rodent and termite problems: Rodrepel™, Termirepel™ and Combirepel™. These are patented non- toxic & non- hazardous products by C-Tech Corporation and have been successful in protecting the polymer applications from the voracious rodents and termites. One of the unique qualities of C Tech Corporation’s repellent products is that they do not kill the target species. These products work on the mechanism of sustainability and green technology. They are therefore significant in today’s time and date as ecology salvation has become the prime focus. Keywords: Polymer applications, Rodents, Pests, Non-toxic, Non-hazardous, Green technology JICABLE15_0137.doc Zanzibar Interconnector 132kV Submarine Cable in Tanzania Yoshiharu NAKAMURA (1), Masanori OTA (1), Robert DONAGHY (2) 1 - VISCAS Corporation, Tokyo, Japan, y-nakamura@viscas.com, m-ohta@viscas.com 2 - ESB International, Dublin, Ireland, robert.donaghy@esbi.ie Zanzibar Island is located off Tanzania in East Africa and in the Indian Ocean. This island recently experienced chronic electricity shortage because of aging of existing equipment. A new 132kV XLPE insulated submarine power cable interconnector was installed to improve power supply reliability and to deal with higher electricity demand in the future. The transmission capacity of this new line is 110 MW. The cable design is three-core with copper conductors and XLPE insulation. The latest manufacturing technology and the excellent quality control system enable lower insulation thickness. The submarine cable has incorporated 24 optical fibers. The choke points of transmission capacity are the shore landing areas for submarine cable, as the thermal resistivity of the landing area is higher than the sea bed and it reduces permissible current carrying capacity of the cable conductor. There are two different conductor sizes in one continuous cable to meet the required transmission capacity. Both ends of the submarine cable lengths contain larger size conductors than the center of the cable. Transition joints and factory joints were made in the factory and the completed cable was delivered with one continuous length. A type test according to CIGRE recommendation was performed to confirm the mechanical and electrical properties of the cable design. The submarine cable was manufactured in VISCAS Ichihara Factory in Japan. After successful factory acceptance test, it was shipped to Africa. In Kenya, the cable was transferred from the cargo vessel to the cable laying barge. The cable laying work from Zanzibar Island to the mainland consisted of 37 km length and maximum 60 m water depth. There are outdoor terminations at shore and the submarine power cable is connected to an overhead transmission line. The construction work was completed in March 2013. This paper will give the outline of the project and design, manufacturing, testing and installation of the submarine cable. JICABLE15_0138.doc Study of the behaviour of a n-metal cable screen subject to an adiabatic short-circuit. Jose María DOMINGO CAPELLA (1) 1 : Grupo General Cable Sistemas SL, Casanova 150, 08036 Barcelona, SPAIN. jmdomingo@generalcable.es The standard IEC 60949 “Calculation of thermally permissible short-circuit currents, taking into account non-adiabatic heating effects” considers only one current carrying component to determine the admissible fault current and duration for a given cable design, as can be seen in the expression found in its point 3 (page 9 of the standard). The Amendment 1 of this standard indicates the possibility of taking into account several carrying conductor components when they are connected in parallel, distributing the fault current among them in inverse proportion to their resistances. This presents a problem whose resolution is not obvious, since components made of metals with different electric resistivity and different temperature coefficients will grow their respective temperatures and resistances at diverse rates. Therefore, during the fault time, the proportion of current carried by each single component will be in constant evolution, leading the whole screen to a situation that will diverge from that obtained assuming fixed current ratios. The lack of a clear procedure showing how this calculation should be made leads very frequently to dimension one of the components to withstand alone the entire fault current. This results into cables that are more expensive, and also a little heavier than necessary. Additionally, the design optimisation will reduce the power losses when the cables are installed in solid-bonding configurations, due to smaller induced currents in the screen. The study first demonstrates that the expression of the point 3 of the standard can be deducted from physical laws. And then it proceeds exactly in the same way to solve the case of several conductor components working in parallel. The result is an analytical expression whose exactitude has been checked with a numerical algorithm that generates a sequence whose limit is the exact solution of the problem. The equation found in the point 3 of the standard is a particular case of the solution of the “nmetal” problem. The main limitation to this study is the assumption of concentricity between all the components involved in the calculation, so it should not be used taking into account the common armour of three core cables, for instance. This is due to the fact that the mutual inductances between the conductor and the screen and other components connected in parallel have not been considered, and in any eccentric configuration they will not be compensated, thus altering the distribution of the current between the different metallic components. Key words Short-circuit calculation; Cable screen; IEC 60949; Cable design JICABLE15_0139.docx Toward acoustic detection of partial discharges in high voltage cables. Tadeusz CZASZEJKO, Jarman A. D. STEPHENS Monash University, Melbourne, Australia, tadeusz.czaszejko@monash.edu Partial discharge (PD) detection by acoustic methods has been commercially available for condition monitoring of overhead line insulators, insulation in power transformers, GIS installations or high voltage capacitors for quite some time. It has been generally regarded as impractical to implement for monitoring PDs in high voltage cables. This is probably the reason why acoustic signal signatures in insulation systems found typically in cables and cable accessories have not been investigated extensively, and as such, they are not very well known. Our recent work has established a good relationship between the size of insulation and the frequency of the acoustic signal emitted [1], [2]. In this context, an application of photonic techniques for the detection of acoustic signals has been also explored. The method employs fiber Bragg grating (FBG) written into optical fiber. An FBG-based device can detect wide spectrum of acoustic signals, which can be an advantage in comparison with piezoelectric transducers that are typically narrow-band. More importantly, optical fiber can be introduced easily into the cable and cable accessories to be near the potential source of partial discharges. Being a purely optical device, it does not require electrical connection to the sensor and it is immune to electromagnetic interference. A generic FBG can be used in laboratory experiments but its sensitivity is not sufficient to be practical for on-line PD detection in cables. This work presents the development of an optoacoustic PD detector with the sensitivity gain of 50-60 dB in comparison with a generic FBG. This was achieved by selecting appropriate material and geometry for housing the sensing part of the fiber. This article describes the process of design and test results of the improved photonic sensor for partial discharge detection that potentially could be used in high voltage cable systems. [1] Czaszejko, T.; Sookun, J., "Acoustic emission from partial discharges in cable termination," Electrical Insulating Materials (ISEIM), Proceedings of 2014 International Conference on , vol., no., pp.42,45, 1-5 June 2014 [2] Czaszejko, T.; Sookun, J., "Acoustic emission from partial discharges in solid dielectrics," Electrical Insulation Conference (EIC), 2014 , vol., no., pp.119,123, 8-11 June 2014. JICABLE15_0140.doc Update on world’s first superconducting cable and fault current limiter installation in a German city center Mark STEMMLE (1), Frank MERSCHEL (2), Mathias NOE (3), Achim HOBL (4) 1 - Nexans Deutschland GmbH, Hannover, Germany, mark.stemmle@nexans.com 2 - RWE Deutschland AG, Essen, Germany, frank.merschel@rwe.com 3 - Karlsruhe Institute of Technology, Karlsruhe, Germany, mathias.noe@kit.edu 4 - Nexans SuperConductors GmbH, Hürth, Germany, achim.hobl@nexans.com In recent years significant progress has been made in the development of high temperature superconducting (HTS) power devices, in particular cables and fault current limiters. Several field tests of large scale prototypes for both applications have been successfully accomplished and the technologies are getting closer to commercialization. Especially the application of medium voltage HTS systems as replacement for conventional high voltage cable systems is very attractive and offers many advantages. Besides the increased power density there is only a negligible thermal impact on the environment. In addition, HTS cables do not exhibit outer magnetic fields during normal operation and in combination with HTS fault current limiters the operating safety is also increased. Since HTS cables are in general more compact than conventional cables the required right of way is much smaller, the installation is easier, and the required substation space is reduced as well. Especially in congested urban areas dismantling of substations results in prime location space gains which could be sold or used otherwise. This paper will give an update on the German AmpaCity project, which started in September 2011. The objective of the project is developing, manufacturing and installing a 10kV, 40 MVA HTS system consisting of a fault current limiter and of a 1 km cable in the city of Essen. Since it is the first time that a one kilometer HTS cable system is installed together with an HTS fault current limiter in a real grid application within a city center area, AmpaCity serves as a lighthouse project. In addition it is worldwide the longest installed HTS cable system. Within the project the development phase was finished in March 2013 with successfully completing the type test of the cable system. Subsequently, all system components were manufactured and the installation on site took about two months finishing at the end of November 2013. Afterwards, the commissioning test of the system was performed in December. In the beginning of March 2014, the system was commissioned into the grid and has since then been supplying energy to the city center of Essen. The widespread use of HTS cables and fault current limiters depends upon the extent to which it is possible to improve the price performance ratio of HTS materials and to optimize manufacturing of cables as well as the cost and reliability of the required cooling technology. It is expected that relatively large technical advances will be made in the future of the comparatively new HTS technology, which in turn will bring associated cost reductions. For this reason, the AmpaCity pilot project in the downtown area of Essen in Germany will be an important step on the way to achieving more widespread application of HTS technology. JICABLE15_0141.docx Development of submarine Aluminum conductor MV-AC power cable with Sven MUELLER-SCHUETZE (1), Heiner OTTERSBERG (1), Carsten SUHR (1), Ingo KRUSCHE (1), Daniel ISUS FEU (2) 1 - Norddeutsche Seekabelwerke GmbH/General Cable, Nordenham (Germany), sven.muellerschuetze@nsw.com, heiner.ottersberg@nsw.com, carsten.suhr@nsw.com, ingo.krusche@nsw.com 2 - General Cable, Manlleu, Barcelona (Spain), disus@generalcables.es A demand exists, mainly driven by the renewable energy sector, to reduce the construction cost of offshore power interconnections between offshore platforms, islands and shore. This demand needs to be addressed through the reduction of both production and material costs of submarine power cables. In this context, both the conductor material selection and the submarine power cable design play crucial roles. Aluminum as conductor material possesses lower conductivity compared to copper resulting in the need to select larger conductor cross sections. Despite the larger conductor cross section, cost reduction is achieved due to the much lower material price of Aluminum. In addition power core and submarine power cable designs were reviewed including the selection of materials and manufacturing techniques. During the development project the materials selection and cable design adjustments were reviewed by theoretical studies and tests to validate the application of the design. The submarine power cable design is intended for installation in water depths up to 300 m and the application of additional cable protection methods such as rock dumping for on-bottom stabilization. A type test qualification has been performed on 3x 800 mm² 19/33 (36)kV XLPE submarine power cable with Aluminum conductor incorporated with one 48-core fibre optic cable. The qualification program was performed under consideration of the Cigre Electra 171, Cigre Electra 189, IEC 60502-2 and Cenelec HD620-10C. The cable system passed successfully all mechanical, electrical and nonelectrical tests. The authors will present the main characteristics of the cable in test, and details the results obtained. JICABLE15_0142.docx A guide for rating calculations of insulated cables Frank DE WILD (1), Jos VAN ROSSUM (2), George ANDERS (3), Bruno BRIJS (4), Rusty BASCOM (5), James PILGRIM (6), Marcio COELHO (7), Georg HUELSKEN (8), Nikola KULJACA (9), Bo MARTINSSON (10), Seok-Hyun NAM (11), Aleksandra RAKOWSKA (12), Christian REMY (13), Tsuguhiro TAKAHASHI (14), Pietro CORSARO (15), Antony FALCONER (16), Alberto GONZALEZ (17), Francis WAITE (18) 1 - DNV-GL, Arnhem, the Netherlands, Frank.deWild@dnvgl.com 2 - Prysmian Group, Delft, the Netherlands, Jos.vanrossum@prysmiangroup.com 3 - Anders Consulting, Toronto, Canada, George.anders@bell.net 4 - Elia Engineering, Brussels, Belgium, Bruno.Brijs@elia-engineering.com 5 - Electrical Consulting Engineers, Schenectady, USA, R.Bascom@ec-engineers.com 6 - University of Southampton, Southampton, UK, jp2@ecs.soton.ac.uk 7 - Procable, Sao Paolo,Brazil, Marcio@procable.com.br 8 - NKT Cables, Köln, German, Georg.huelsken@nktcables.com 9 - Prysmian Group, Milan, Italy, Nikola.Kuljaca@prysmiangroup.com 10 - ABB, Karlskrona, Sweden, Bo.Martinsson@se.abb.com 11 - LS cable Ltd, Gyeongbuk, Korea, shnam@lscns.com 12 - Poznan University of Technology, Poznan, Poland, Aleksandra.Rakowska@put.poznan.pl 13 - Prysmian Group, Gron, France, Christian.Remy@prysmiangroup.com 14 - CRIEPI, Nagasaka, Japan, Shodai@criepi.denken.or.jp 15 - Brugg cable, Brugg, Switzerland, Pietro.corsaro@Brugg.com 16 - Aberdare Cables, Port Elizabeth, South Africa, afalconer@aberdare.co.za 17 - GasNatural Fenosa, Madrid, Spain, agonzalezsan@gasnatural.com 18 - National Grid, Warwick, UK, Francis.Waite@uk.ngrid.com Cigre SC B1 set up Working Group B1-35 to consider the subject of cable rating in 2010. Cable rating is a very important topic for all in the cable industry. The goal of the working group has been to provide guidance to a user trying to calculate, or to understand the current rating of a power cable system in any occurring situation. This article is one of the first deliverables of the working group and introduces in a concise yet precise way the contents of the work, important eye openers and needed considerations for the user in the quest to understand the current rating of the power cable in his or her situation. From a utility perspective, the cable rating is amongst the most important requirements for a power cable. Therefore, utilities often focus on the subject of cable rating during: 1 The design and engineering phase, where the cable rating is usually calculated by the manufacturer, and has to be in correspondence with a certain requirement (either stationary or dynamic) set by the utility. This theoretical exercise is often the only background of a cable’s current rating as testing the cable rating is not an often used option. 2 The operation phase of power cables, where cables often become increasingly loaded. For utilities it is not easy to set the current rating requirements for the 30 - 50 years to come, as there are very many rapid changes in the world of electric energy generation and transmission & distribution. Existing power cables may come in a situation where the load is more than allowable according to the (old) engineering calculations. In these situations it is becoming very important to know the exact limitations regarding the cable rating, in order to prevent acute overloading, and to invest in time in new transmission facilities. JICABLE15_0142.docx This utilisation leads to the need to establish an accurate cable rating for each power cable system whatever its situation or age. There are however difficulties with this, as the variety in cable designs and installation situations differs to a much larger extend than the breadth of the calculation options in existing standards. For this reason, WGB1-35 considered the current rating of insulated power cables, including buried, submarine and in-air installations, in detail, addressing problems with establishing the ampacity of new and existing power cables. The workgroup focused on the following three major topics: - A consideration of the starting points for cable rating calculations A guide to methods for calculating the current rating in situations which are not (fully) described in the existing IEC standards - A discussion concerning the tools and techniques available for performing cable rating calculations. The important learning points, insights, eye openers and proposals on these three major topics will be shared in this Jicable article as a concise summary in order to provide further guidance in the topic of cable current rating calculations. JICABLE15_0143.docx Experience and Challenge of Cable connections of Offshore Wind Farms in German North Sea Volker WERLE, Dr. Dongping ZHANG, Dr. Jochen JUNG 1 - TenneT TSO GmbH, Germany, Asset Management Offshore, volker.werle@tennet.eu dongping.zhang@tennet.eu ; jochen.jung@tennet.eu Starting in 2006 with the connection of Germany’s first offshore wind park (OWP) alpha ventus, TenneT Offshore GmbH (former E.ON Netz Offshore and Transpower Offshore GmbH) implemented various connections of OWP to the German grid. As most of the OWP’s are situated far away from the coast on the continental shelf of the North Sea and all the sea cables cross the UNESCO natural reserve Wadden Sea generating additional environmental restrictions, only three OWP’s could be connected with HVAC. For the time of this publication four HVDC grid connection projects are in test operation and one HVDC cable connection has passed the final installation test and will start test operation soon. Alpha ventus - the first German offshore grid connection project 110kV AC, 60 MW, 60 km offshore and 6 km onshore, in continuous operation since spring 2009. BorWin1 150kV DC, 400 MW, 125 km offshore and 75 km onshore, in operation since May 2011. BorWin2, DolWin1 and HelWin1 o HelWin1: 250 DC, 576 MW, 85 km offshore and 45 km onshore, in test operation with two OWP’s connected o BorWin2: 300kV DC, 800 MW, 125 km offshore and 75 km onshore, test operation started recently with one OWP connected o DolWin1: 320kV, 800 MW, 75 km offshore and 95 km onshore, in test operation, two OWP’s connected SylWin1 SylWin1: 320kV, 864 MW, 160 km offshore and 45 km onshore, final cable installation test passed, test operation starting soon This paper will present an overview of the challenge and the experience with now three HVAC- and four HVDC-systems in operation: Cable design, manufacturing and testing o Increasing voltage levels and long cable routes with many joints onshore o After installation tests of long cable length with many joints o Monitoring of health status and preventative cable repair measures Cable laying and burial o Cable routes with cable laying activities of different projects in the same time window o Environmental restrictions like narrow time slots for cable laying activities o HDD (Horizontal Direct Drilling) with length more than 1300 m o UXO (Unexploded Ordnance) along sea cable routes o Laying methods to meet the burial depth requirements Environmental protection (locations system and temperature monitoring) o Observing the 2K-criteria in sight of changing OWP arrangements and upgrading of existing windmills o Cable location systems to monitor the cable position to verify the compliance with permissions JICABLE15_0144.docx Development of dynamic submarine MV power cable design solutions for floating offshore renewable energy applications Marco MARTA (1), Sven MUELLER-SCHUETZE (1), Heiner OTTERSBERG (1), Daniel ISUS (2), Lars JOHANNING (3), Philipp R THIES (3) 1 - Norddeutsche Seekabelwerke GmbH/General Cable (NSW), Nordenham, Germany, marco.marta@nsw.com, Sven.Mueller-Schuetze@nsw.com, Heiner.Ottersberg@nsw.com 2 - General Cable Sistemas, Manlleu, Spain, disus@generalcable.es 3 - University of Exeter, Penryn, UK, L.Johanning@exeter.ac.uk, P.R.Thies@exeter.ac.uk Floating offshore renewable energy (ORE) can potentially provide a significant share of the future energy generation mix. Floating foundations may greatly expand offshore wind deployment areas by overcoming water depth constraints. Additionally, floating wind gives access to manufacturing and deployment practices that may deliver significant cost reductions. Few full size floating wind prototypes have been installed with more deployments announced. Developers of both wave and tidal energy converters are also deploying an increasing number of floating prototypes. Most floating ORE connections to the power grid require submarine power cables capable of withstanding continuous dynamic mechanical loading regime during their lifetime. NSW have considerable experience in the design and development of dynamic cables, mainly for oil and gas applications. While design practices are transferrable, typical floating ORE system configurations and operating modes result in distinctive power cables loading regimes and functional requirements that demand specific design solutions. This paper reviews approaches to design, modelling and testing of submarine dynamic power cables for floating ORE systems requirements. It mainly focuses on loading regime estimation in highly dynamic working conditions, mechanical design methodologies and assessment of cable strength and fatigue life. In order to account for the variety of floating ORE devices characteristics, a loading regime envelope is defined for both extreme and cyclic loads based on the analysis of a representative selection of floating ORE technologies. Global load regimes are estimated and the related stress distribution within the cable structure is calculated using a combined approach of FEA modelling and cable structural analysis. Some examples of different cable structural arrangements are presented together with their performance assessment under the given loading conditions including the identification of critical components damage and failure modes. Design assumptions were validated and/or calibrated through a test program that subjected a selection of cables and associated components to both extreme and cyclic loading regimes. The test program especially focused on the assessment of fatigue failure modes and fatigue life estimation methods. It included a combination of standard methods, novel test configurations and detailed component and materials analysis. The modelling and test results informed the design of a prototype cable that was manufactured and then subjected to a further cycle of accelerated testing. The paper presents the cable performance assessment results. The project enabled to further strengthen NSW’s capabilities in modelling, design and testing of dynamic submarine power cables, with a focus on specific solutions for floating ORE systems requirements. JICABLE15_0145.doc Degradation Mechanism of SCOF Cable Due to Cable Core Movement Yuji MATSUYA (1), Takeshi KAYA (1), Manabu SOGA (1), Takahiko TSUTSUMI (2), Gaku OKAMOTO (2), Hideyuki ITABASHI (3), Yasuichi MITSUYAMA (3) 1 - The Kansai Electric Power Co., Inc., Osaka, Japan, matsuya.yuuji@c4.kepco.co.jp, kaya.takeshi@c5.kepco.co.jp, soga.manabu@e5.kepco.co.jp 2 - J-Power Systems Corporation, Osaka, Japan, tsutsumi.takahiko@jpowers.co.jp, g.okamoto@jpowers.co.jp 3 - VISCAS Corporation, Tokyo, Japan, h-itabashi@viscas.com, y-mitsuyama@viscas.com In Japan, electric power cables are applied up to 500kV and are important in power system configurations in urban areas. Among these applications, self-contained oil-filled (SCOF) cables account for 22%. Many SCOF cable facilities have started operating since the 1960s and 1970s. Recently, we have experienced some SCOF cable breakdown accidents and considered that the breakdown in the Kansai Electric Power Company (KEPCO) area was caused by cable core movement. Therefore, we investigated the joint boxes that were broken and removed. This paper introduces the degradation mechanism and maintenance procedure obtained from the investigation of the joint boxes that were broken and removed. Many factors cause degradation of SCOF cables, namely, thermal expansion, negative oil pressure, oil leakage, and insulation impurities, among others. These might have caused partial discharge or overheating inside the SCOF cables, carbonizing the cable insulating papers, and finally degrading the electrical performance. This study focuses on the cable core movement where relative displacement between the cable core and metal sheath occurred due to cable core longitudinal movement following thermal expansion and difference in the axial force. Cable thermal expansion is caused by load and ambient temperature changes. The difference in axial force is caused by some cable layout conditions such as steep slope and cable curve near joint boxes. We calculated the estimated cable core displacement. Inside a joint box, old type semi-stop parts (which are applied to temporarily stop the oil during jointing works) can exert strong binding force on the cable core. Cable core movement can possibly disarray the laminated structure of the insulating paper locked by the semi-stop. Then, oil gaps are formed at the cable core, causing step partial discharge and eventual cable breakdown. Cable core movement under some cable conditions, and strong binding force by the semi-stop parts might have all caused the breakdown accidents of the SCOF cable joint boxes (over 154kV) in the KEPCO area, except for defective design, manufacturing failure, assembly failure. During the investigation of the joint boxes, evidence of cable core movement was found, for example, deformation in the semi-stop and disarray in the shielding layer. Disarray in the oil gap intervals and extensive carbonization were also found. The insulating layer thickness of the cable core was carbonized by more than 30%. X-ray photography can confirm cable core movement inside the joint box. However, X-ray photography cannot confirm the carbonization that is the cause of the electrical performance degradation. Dissolved gas analysis can confirm the occurrence of partial discharge inside the joint box. However, detecting the dissolved gas generated in the cable core by partial discharge is difficult using usual oilsampling approach. Therefore, developing abnormality determination criteria are important. Recently, new criteria that focus on various dissolved gas have been suggested, which are considered desirable in maintaining the SCOF cables. We hope to prevent further SCOF cable breakdown by continuously investigating the removed joint boxes and considering and implementing as-needed maintenance procedures that address degradation due to the cable core movement and other deterioration. JICABLE15_0146.doc CIGRE WG B1.34: Mechanical Forces with Large Conductor Cross Section XLPE Cables J. KAUMANNS (1), M. BACCHINI (2), G. GEHLIN (3), B. GREGORY (4), D. JOHNSON (5), T. KURATA (6), H.-P. MAY (7), C. PYE (8), R. REINOSO (9), J. SAMUEL (10), J. TARNOWSKI (11), R. v. d. THILLART (12), M. A. VILHELMSEN (13), D. WALD (14) 1 - LS Cable&System Ltd., Gumi, South Korea, jkaumanns@lscns.com 2 - Prysmian, Italy 3 - Svenska Kraftnaet, Sweden 4 - Cable Consulting International Ltd., United Kingdom 5 - Powereng, Unites States of America 6 - J-Power System Corporation, Japan 7 - nkt cables, Germany 8 - MottMcDonald, Ireland 9 - Red Electrica, Spain 10 - Nexans, France 11 - IREQ, Canada 12 - Tennet, The Netherlands 13 - Energienet.dk, Denmark 14 - Eifelkabel, Switzerland This paper summarizes the work of CIGRE working group B1.34 dealing with the topic of the thermomechanical forces involved with large conductor XLPE cable systems. Such forces can reach several tons of axial thrust and/or significant cycling movements in the cable system installed. The complexity of the physical nature of the problem disallows an easy calculation of the related effects (non linear effects, hysteresis effects, etc.): Therefore, measurements on full size cable samples and best practice experiences are needed to design a safe cable system. The paper gives an overview about the different design approaches in four sections: - Rigid cable systems - Flexible cable systems - Transition sections between rigid and flexible installations and - Duct installation. Each section describes the individual complexity, explains the background and gives a guidance on how to handle the individual topics: The state of art design rules are given and examples for installation with good experiences related to thermo-mechanical issues are shown. A special section deals with the topic of installations clamps (or cleats), which are an important installation tool to handle the thermo-mechancal forces in a cable system, but not always consid. In order to get input data for the design formulas, different measurement methods are described which are needed to get the specific mechanical cable values for: - Linear expansion coefficient - Axial stiffness EA - Bending stiffness EI. The general basics of the design principles and the thermo-mechanical model, which are described in the CIGRE brochure 194 are followed, but a deeper background is given. Wherever needed, deviation to the CIGRE brochure 194 is explained as most of the experiences were formerly based on paper insulated cable systems, which can behave differently from XLPE insulated cable systems. Overall, the new brochure is a guide on how to handle this topic and gives a broad overview of the best practices around the world. JICABLE15_0147.doc Type test and special tension test of 230kV XLPE submarine cable system Satoshi ONA (1), Tatsuya KAZAMA (1), Takehiro NOZAKI (1), Shoji MASHIO (1) 1 - J-POWER SYSTEMS, 1-1-3, Shimaya, Konohana-ku, Osaka, 554-0024 Japan, ona.satoshi@jpowers.co.jp, kazama.tatsuya@jpowers.co.jp, nozaki.takehiro@jpowers.co.jp, mashio@jpowers.co.jp, A new 230kV AC transmission line will be installed in San Francisco area in 2015. The line consists of 5 km submarine route in length containing 4 km of marine route, 0.4 km of landfall section constructed by horizontal directional drill (HDD) at each end, and 0.8 km of underground on-shore section. The maximum water depth is 40m and the rated capacity is 400 MVA. The specification of submarine cable is single core, 1400 mm2 Keystone conductor, cross-linked polyethylene insulated, lead alloy sheathed, semi-conductive polyethylene sheathed and double copper wire armored submarine power cable with embedded optical fibers. The longitudinal water blocking materials are applied in the conductor and under lead sheath. In order to achieve the high transmission capacity, copper flat wires are applied for armoring instead of steel wires. San Francisco is located inside the Pacific Rim. In order to endure the seismic tension more than 20 ton, the double copper wire armors are applied with contra-helical. Moreover, the prefabricated joint and armor clamps shall be installed inside the jointing manhole between the submarine and land cable. In order to confirm the mechanical, electrical and water blocking performance of these cable and accessories, the type test and tension test are specified and conducted prior to shipment. The tension tests with straight and offset shape were performed for simulation of the installed cable configuration in off-shore and in manhole respectively. The straight tension test is conducted to confirm the soundness of submarine cable after loading of tension. The purpose of offset shape tension test is to check the soundness of armor clamp and to observe the residual cable core tension given to joint. On site, the cable offset will be made between the clamp and joint in order to provide slack and to reduce the seismic tension given to joint. These tension tests were performed with 31 ton and 46 ton tension. 31 ton is the limitation of cable tension capacity by some design standard. If the cable tension capacity can increased be up to 46(=1.5×31) ton, the failure probability of cable by the seismic at magnitude 7.8 can be reduced from 20% to 9%. During the testing, the cable and armor clamps withstood 31ton and 46ton tensions with both straight and offset shape. After the tension test, the cable passed the 332kV (2.5U0) for 30 min and no partial discharge was detected at 200kV (1.5U0). The type test is performed in accordance with CIGRE TB490 except the conductor temperature 105C to satisfy both IEC 62067 and AEIC CS9. The cable sample was subjected to tensile bending test at 19.6 kN/m in accordance with Electra 171. In the loop of electrical type test, the submarine cable, land cable, SF6 gas termination, prefabricated joint, repair joint and armor clamp were installed. After 20 times heat cycle, the partial discharge test, lightning impulse voltage test followed by voltage test and examination of cable system are performed. This high standard cable system design would contribute to the reliable operation for the supply of electricity. Key words Submarine cable; Keystone conductor; Seismic design; Copper wire armor; Armor Clamp JICABLE15_0148.doc Ultra-Fast Distributed Temperature Sensing: A new approach to temperature measurement in underground cables Xabier BALZA (1), Javier BENGOECHEA (2) 1 - General Cable, Barcelona, SPAIN, xbalza@generalcable.e 2 - Lumiker, Bilbao, SPAIN, javier.bengoechea@lumiker.com The development of a new technique of data acquisition has allowed to a new Brillouin based Distributed Temperature Sensing (DTS) system to measure lengths of tens of kilometers with refresh times of milliseconds and with precisions around 1 ºC. This opens the door to a new concept called Ultra-Fast Distributed Temperature Sensing (UFDTS) that makes possible not only to monitor the service temperature faster than ever, but to pre-localize cable faults and exploit cables in low thermal inertia environments such as galleries with better accuracy and safety. While standard DTS systems have minutes, or seconds depending on the length and the precision, of measurement refreshing time, the capability of having high precision measurements with refreshing times within the duration of the short-circuits gives a new added value to the presence of fiber optics inside or by the HV or MV cables. This article describes the new data acquisition technique, the main features achievable with new UFDTS equipment and the new foreseen applications. JICABLE15_0149.doc Operating Records and Recent Technology of DTS System and Dynamic Rating System (DRS) Tsunefumi WATANABE (1), Yoshimasa MURAMATSU (1), Masaharu NAKANISHI (1) 1. J-Power Systems Corp., 1-1-3 Shimaya Konohana-ku Osaka, JAPAN watanabe.tsunefumi@jpowers.co.jp, muramatsu.yoshimasa@jpowers.co, nakanishi.masaharu@jpowers.co.jp Distributed Temperature Sensing (DTS) system is utilized for power cable temperature monitoring regarding its long length distributing measurement capability. Dynamic Rating System (DRS) which is a combination of the temperature and the real-time cable load current, calculates the conductor temperature in real time based on IEC standard formula, and activate alarms if the conductor temperature exceeds the permissible level in real time monitoring. It also calculates the emergency overload current which considers the surrounding soil temperature raise in future through the thermal diffusive models. They all are done on real-time basis so that they contribute the cable system operation and maintenance. DTS fibers are basically attached on or incorporated in the power cables, but also are installed in the communication conduits attached outside of the cable conduits for some cables laid in conduits. In the case of conductor temperature calculation from outside of conduits, the calculation parameter between the cable surface and DTS fibers shall be calibrated since the parameter of IEC standard tends to be conservative. Some experiments are done for calibrating the parameters. In addition, some DTS fibers are taped on the cables during the cable pulling into conduits in actual installation. Those fibers are used as a reference point sensor to measure the cable surface temperature for evaluation and fine tuning of the parameters. JPS has been supplying the DTS system as a cable manufacturer, as well as the Dynamic Rating System (DRS) and those systems have more than 15 years operation history. Installed DRS has acquired the historical data such as deep underground temperature and equivalent thermal resistance, which provided relevant thermal data in that region and contributed to the cable system design as well. Some hot-spot has been found and was taken into account for cable grid operation. For the discussion of DRS modeling, the thermal diffusive model has been adopted for overload calculation with a constant of thermal resistivity in soil. However, thermal resistivity would vary in time therefore, in the prediction of overload rating, a considerable high value is used at the place, which would result in the pessimistic overload value rather than actual capacity. Therefore, some of recent DRS have a function to compare the measured temperature and the predicted temperature calculated by actual load data based on the programmed thermal resistivity, which are able to evaluate the actual thermal constant and adjust thermal constant in model for further accurate monitoring. This paper describes those experiences and challenges on DTS and DRS. JICABLE15_0150.docx Influence of heat-shrink joints and terminations on Tan delta values of a medium voltage cable installation at very low frequency. Theresa JOUBERT (1), Jerry WALKER (2) 1-Vaal University of Technology, Vanderbijlpark, South Africa, theresa@vut.ac.za 2-Walmet Technologies (Pty) Ltd, Vereeniging, South Africa, jerrywalker@walmet.co.za Medium voltage cables and the accessories (joints and terminations) form a critical part of the power delivery system. While progress has been made in understanding the processes in the accessories of power cables during diagnostic testing with power frequencies, the processes during testing with other frequencies are not known yet and this necessitates that several aspects require considerable investigations to obtain further information. High voltage testing of cables are done to verify the integrity of the accessories after installation on a new cable system and as a control measure of the jointing process on a service aged cable and its accessories following a failure. It is an accepted practice to perform the tests with a low frequency supply due to the constraints of testing at power frequency and thus field testing of Medium Voltage cables are done at very low frequency (0.1 Hz) and it has also been incorporated into the National Standards of many countries (SANS 10198-13). It has further become very popular to also incorporate diagnostic testing and evaluation of the cable systems at very low frequency and partial discharge and Tan delta evaluation are the two popular methods. It has been shown in a number of publications that the Tan delta value of a heat shrink joint and termination are not a direct function of the frequency as is the case with a single layer of insulation like an XLPE cable. In a multi-layer insulation system like a joint and / or termination the polarization characteristics of the different materials play a significant role at very low frequencies having a significant effect again on the Tan delta value. Therefore, cable accessories should be treated quite differently from the cables itself as the joint in a cable system is a complex multi-layer insulation system whilst the cable can be seen as a homogeneous insulation system. Most standard tests ignore the effect of the frequencies and wave shape on the accessories of a complex multi-layer insulation system. The differences of the permittivity and volume resistivity of the materials of the different layers have the effect that the combination of materials (three layers and two layers) will respond differently to varying frequencies as the mechanisms involved to determine the stress distribution in a joint, is totally different to a cable which is a single layer insulation system. It is therefore necessary to understand the behaviour of multi-layer insulation systems when a test is performed at a frequency lower than the rated frequency in order to do a sound evaluation of the condition of the insulation. Finite Element Simulations has been used to determine the theoretical Tan delta values of Cables, joints and terminations in isolation. This paper combines all the previous simulation results to show the influence of joints and terminations as a function of the length of the cable system and the number of joints in the cable system. JICABLE15_0151.doc CPR (Construction Products Regulation) on medium and low voltage distribution cables for Spanish electric utilities Neus GENERÓ (1), Daniel CALVERAS (1), Francesc PADILLO (2), Manel MAURI (2), Jordi BARGALLÓ (3) 1 - Grupo General Cable Sistemas, S.L.U., Manlleu, Spain, ngenero@generalcable.es dcalveras@generalcable.es 2 - Prysmian Spain, S.A., Vilanova i la Geltrú, Spain, francesc.padillo@prysmiangroup.com, manel.mauri@prysmiangroup.com 3 - Top Cable, S.A., Rubí, Spain, jbargallo@topcable.com The report presented in Jicable’11 entitled “Study on the reaction to fire of medium voltage cables systems”, established the most appropriate protection to use in medium voltage cables systems for electric utilities, considering the efficacy of cables by themselves, different coatings applied and, finally, the effect of the accessories. From that project, the best solution has been provided for medium voltage cables successfully overcoming the IEC 60332-3 fire reaction test. Nowadays the current fire protection scenario for construction cables and thus for medium and low voltage distribution cables installed in galleries and substations is about to change in the next months. In Spain, electric utilities have indicated a readiness to adopt the new Construction Products Regulation (CPR) as soon as possible, that is, from June 2015. The called CPR is the Construction Products Regulation, which will mean a technological barriers suppression to favour the free commerce of construction products, always securing a minimum quality requirements. Under the CPR, it will become mandatory for manufacturers to apply CE marking to any of their products which are covered by a harmonised European standard (hEN) or European Technical Assessment (ETA). It is important to note that if a country does not have a legislative regulation regarding fire performance on distribution cables, then that country has not the obligation to adopt the CPR. In Spain there is a fire performance regulation, so the CPR has to be adopted for those cables. So it is time to go ahead and make a step further in relation to reaction to fire performance. The new CPR test applied to cables is not only covering the flame spread (as until today) but also the heat release, smoke production, flaming droplets and acidity during the fire reaction test. The uncertainty created by the new CPR test and the willingness to be pioneers in its implementation on electric utilities cables led to this project, thanks to the work being done by the three main manufacturers General Cable, Prysmian and Top Cable. The study is carrying out using as a reference the test to EN 50399 (Common test methods for cables under fire conditions - Heat release and smoke production measurement on cables during flame spread test - Test apparatus, procedures, results). Medium and low voltage distribution cables for the Spanish electric utilities are being tested in order to have the real scenario of fire reaction performance according to the new system established by the CPR. Knowing which is the situation according to the new CPR test for current cables (normally overcoming the IEC 60332-3) is a must and also a opportunity to improve the designs once determined the new fire performance status. JICABLE E15_0152.do ocx Unde erground d mana agementt pow wer cab ble he ealth in ndexing g and risk Sander M MEIJER (1), Peter VAN DER WIELE EN (2), Misch ha VERMEER R (3), Jos W WETZER (4), Evertt DE HAAN (5) ( 1 - DNV GL, Arnhem m, The Netherlands, sand der.meijer@d dnvgl.com , peter.vanderw p wielen@dnvgl.com, misch ha.vermeer@ @dnvgl.com, jos.wetzer@ @dnvgl.com, evert.dehaan@dnvgl.com m Nowadays, network operators are facing cha allenges in managing their grid effectivvely and in meeting m a range off increasing stakeholder performance s e demands (s safety, reliab bility, environnmental, and d financial impact). Meanwhile, the underg ground powe er cables ins stalled throug ghout the grrids are con ntinuously ageing, increasing the failure prrobability an d associated d risks. As a result, estiimating the expected time to fa ailure and tim mely taking mitigating m me easures beco omes more relevant by thhe day. Among tthe substantial amount and a diversity of undergro ound power cables c foundd in modern electricity e networkss, each having its speciffic inherent a ageing behav viour and failure impact, the asset manager's m challeng ge is to decide which cable circuits req quire attentio on first and what w actions need to be taken. To give a asset manag gers insight into the requ ired long-terrm maintenan nce and repllacement acttivities an advance ed health indexing and risk assesssment mode el for underg ground pow wer cables has h been develope ed and imple emented. Based o on CIGRE Te echnical Broc chure 358 - Remaining Life L Managem ment of Exissting AC und derground Lines - a and in-house e experience e, a library o of condition--assessmentt algorithms was developed. The health in ndexing mode el uses these e algorithmss to assess th he asset rem maining life (liinked to prob bability of failure) a and the time to additional maintenancce. Through the use of Monte M Carlo ssimulations the model is able to determine a certaiinty level to o the assessm ment. The mod del uses da ata from a variety v of so ources such as cable syste em specific data: d age, ra atings, loading data, short--circuit curre ents, failure data and cond dition data; and a more general data: ty typical ageing trrends and fa ailure statistic cs. In case d data is missing or inaccurrate, deducttion modelss and statistica al inference are used to provide best estimate es. The mod del provides s clear overrviews and visu ualizations for f asset managers m to help them ovversee the health deve elopment off their overall a asset base down d to each individual cable circuit in detail. Modern network ope erators use a risk-based asset evalu uation to sup pport decisioon making. Therefore, T one nee eds to estim mate the imp pact of a cab ble failure and a prioritize e all circuits on the bas sis of the resulting g risk. Thereffore, in an additional a mo odel, the dettermined hea alth indices oof the cable systems my and environment, are being combined with selecte ed business values, like safety, reliability, econom to end u up with the overall o risk per cable ci rcuit. Relate ed risk matrix plots visuaalize the various risk results. This all ena ables clear and a structure ed overviews s for asset managers m too support ap ppropriate actions a at the right tim me. JICABLE15_0153.docx Study of the applications thermal ageing of the XLPE for HVDC Justine BILLORE (1,2,3), Jean-Louis AUGE (1,3), Sébastien PRUVOST (2), Olivier GAIN (2), Charles JOUBERT (1), Arnaud ALLAIS (3), Michaël DARQUES (3), Wilfried FRELIN (3) 1 - Laboratoire Ampère, UMR 5005, Villeurbanne, France, justine.billore@univ-lyon1.fr, jeanlouis.auge@univ-lyon1.fr , charles.joubert@univ-lyon1.fr 2 - Laboratoire IMP, UMR 5223, Villeurbanne, France, sebastien.pruvost@insa-lyon.fr , olivier.gain@univ-lyon1.fr 3 - SuperGrid Institute, Villeurbanne, France, arnaud.allais@nexans.com , michael.darques@nexans.com , wilfried.frelin@edf.fr Electricity networks of the future are moving towards supergrid networks. These networks will use HVDC voltage to supply center of consumption from sources that are far from them or to connect different countries together. The objective is to ensure network stability and security, especially with contribution renewable energies like large off-shore wind farms and solar plants. In some areas the HVDC network is mainly based on submarine and land. The reliability of the cables depends strongly of the quality of the synthetic insulation based on cross-linked-polyethylene (XLPE). The objective of this paper is to propose characterization methods of the XLPE insulation before and after thermal ageing. In order to identify some ageing makers, the insulating material is studied by physical-chemical techniques. Among the available techniques, Differential Scanning Calorimetry (DSC), the Fourier Transform InfraRed spectroscopy (FTIR) and the thermo gravimetric analysis (TGA) can already give good markers of the evolution of the vulcanized polymer morphology. Consistent evolutions of melting temperature, cristallinity and presence of carbonyle, CH2 and CH3 groups gives trends of the physic-chemical ageing and potential impacts on properties of XLPE. Keywords: XLPE, DSC, TGA, FTIR, XRD, thermal ageing JICABLE15_0154.doc Development and high temperature qualification of innovative 320kV DC cable with superiorly stable insulation system Marco ALBERTINI (1), Alberto BAREGGI (1), Paolo BOFFI (2), Luigi CAIMI (1), Luca DE RAI (1), Stefano FRANCHI BONONI (1), Giovanni POZZATI (1) 1 - Prysmian SPA, Viale Sarca 222, 20126 Milano, ITALY. marco.albertini@prysmiangroup.com, alberto.bareggi@prysmiangroup.com, luigi.caimi@prysmiangroup.com, luca.derai@prysmiangroup.com, stefano.franchibononi@prysmiangroup.com, giovanni.pozzati@prysmiangroup.com 2 - Prysmian Cavi e Sistemi SRL, Viale Sarca 222, 20126 Milano, ITALY. paolo.boffi@prysmiangroup.com The big demand for transmission of high electrical power in long distances has brought to the fast and successful development in the recent years of HVDC Transmission Systems at increasingly current and voltage levels. 320kV DC cable systems have been developed, qualified and installed in numerous cases and the way to increase voltage levels and conductor sizes looks to be still well far from the finish line. The big majority of the HVDC systems today qualified is based on the use of XLPE insulated cables, which performances are very well known and appreciated as far as HVAC systems are concerned as well. In the case of HVDC XLPE insulated cable systems, big accent must be given to the necessity of degassing the insulation material after crosslinking, as the presence of the by-products can play a very negative role in terms of insulation electrical resistivity and of space charge accumulation and consequently of the electrical properties in DC of the cable itself. In this sense very long degassing times for the insulated cores is the solution commonly adopted for reducing the effect of the byproducts and stabilizing the electrical properties of the cable to values affordable at the high electrical gradients of the modern HVDC cable systems. The degassing times practically applied for HVDC cables are indeed even significantly higher than the times applied to HV and EHV cables for use in AC systems. In this situation it looks very attractive to develop a cable system that, without penalizing the general performances of the transmission system (namely the maximum current transmissible), doesn’t require a chemical crosslinking treatment during the production process, aimed to create the molecular interconnections in the polymeric insulation structure; and that consequently could be characterized by a changeless insulation system with steady and abiding electrical properties. Recently developed cables with P-Laser technology, based on fully thermoplastic PP insulation with enhanced thermo-mechanical properties, provides nowadays an undisputable track record in Italian Power Distribution network, reinforced by the recent installation and plug-in of the first 150kV cable system in Italian Transmission network (Lacchiarella project); for this reason P-Laser takes the form of a veritable starting point for the development of the above mentioned superiorly stable HVDC insulation systems. The paper describes the activity performed in terms of development of the new insulation for HVDC cables based on P-Laser technology, tests on model cables, production of prototype for 320kV insulation class, electrical assessment of the prototype and subsequent PQT performed at 90°C on a complete system, based on Cigrè recommendation TB 496. JICABLE15_0154.docx Development and high temperature qualification of innovative 320kV DC cable with superiorly stable insulation system Marco ALBERTINI (1), Alberto BAREGGI (1), Paolo BOFFI (2), Luigi CAIMI (1), Luca DE RAI (1), Stefano FRANCHI BONONI (1), Giovanni POZZATI (1) 1 - Prysmian SPA, Viale Sarca 222, 20126 Milano, ITALY. marco.albertini@prysmiangroup.com, alberto.bareggi@prysmiangroup.com, luigi.caimi@prysmiangroup.com, luca.derai@prysmiangroup.com, stefano.franchibononi@prysmiangroup.com, giovanni.pozzati@prysmiangroup.com 2 - Prysmian Cavi e Sistemi SRL, Viale Sarca 222, 20126 Milano, ITALY. paolo.boffi@prysmiangroup.com The big demand for transmission of high electrical power in long distances has brought to the fast and successful development in the recent years of HVDC Transmission Systems at increasingly current and voltage levels. 320kV DC cable systems have been developed, qualified and installed in numerous cases and the way to increase voltage levels and conductor sizes looks to be still well far from the finish line. The big majority of the HVDC systems today qualified is based on the use of XLPE insulated cables, which performances are very well known and appreciated as far as HVAC systems are concerned as well. In the case of HVDC XLPE insulated cable systems, big accent must be given to the necessity of degassing the insulation material after crosslinking, as the presence of the by-products can play a very negative role in terms of insulation electrical resistivity and of space charge accumulation and consequently of the electrical properties in DC of the cable itself. In this sense very long degassing times for the insulated cores is the solution commonly adopted for reducing the effect of the byproducts and stabilizing the electrical properties of the cable to values affordable at the high electrical gradients of the modern HVDC cable systems. The degassing times practically applied for HVDC cables are indeed even significantly higher than the times applied to HV and EHV cables for use in AC systems. In this situation it looks very attractive to develop a cable system that, without penalizing the general performances of the transmission system (namely the maximum current transmissible), doesn’t require a chemical crosslinking treatment during the production process, aimed to create the molecular interconnections in the polymeric insulation structure; and that consequently could be characterized by a changeless insulation system with steady and abiding electrical properties. Recently developed cables with P-Laser technology, based on fully thermoplastic PP insulation with enhanced thermo-mechanical properties, provides nowadays an undisputable track record in Italian Power Distribution network, reinforced by the recent installation and plug-in of the first 150kV cable system in Italian Transmission network (Lacchiarella project); for this reason P-Laser takes the form of a veritable starting point for the development of the above mentioned superiorly stable HVDC insulation systems. The paper describes the activity performed in terms of development of the new insulation for HVDC cables based on P-Laser technology, tests on model cables, production of prototype for 320kV insulation class, electrical assessment of the prototype and subsequent PQT performed at 90°C on a complete system, based on Cigrè recommendation TB 496. JICABLE E15_0155.do ocx Risk on failure, ba ased on n PD measurem ments i n actua al MV PILC and XLPE pow wer cable es Yizhou Q QIAN (1), Pa aul WAGENA AARS (2), Frred STEENN NIS (3), Denn ny HARMSEN N (4), Piet SOEP PBOER (5), Pascal BLEE EKER (6) 1 - Technical Universsity Eindhove en, Eindhove en, the Nethe erlands, q5022679@1633.com 2 - DNV GL, Arnhem m, the Netherrlands, paul.w wagenaars@ @dnvgl.com 3 - DNV GL, Arnhem m, the Netherrlands, fred.ssteennis@dn nvgl.com 4 - Allian nder, Arnhem m, the Netherrlands, dennyy.harmsen@ @alliander.com 5 - Enexxis, Arnhem, the Netherla ands, piet.soe epboer@ene exis.nl 6 - Locamation, Enscchede, the Netherlands, N pascal.bleek ker@locamattion.nl Many pa apers discusss partial disc charge (PD) a activity as measured d during an offf-line test in actual a MV po ower cables or o over time, ass measured during d labora atory circums stances. Seldomlyy, actual PD developmen nt is measure ed as a func ction of time under u servicee circumstan nces, and certainlyy not (often) under service condition ns until an actual a failure happens. F For the first time this critical a and crucial in nformation is now made available on a large scale, following measureme ents done with Sma art Cable Gu uard (SCG). al, since nettwork owners The information on PD P developm ment is crucia s have to knnow whether a certain PD gene erating comp ponent needs s to be replacced or not, in n case of measured PD aactivity. This pap per will show w the average e duration be etween the start of PD ac ctivity and thee moment off a failure based on actual me easurements. It will be s hown that in n case of MV V XLPE insuulated cable systems (cable, jo oints or term minations), th he time until failure is we eeks or montths (dependi ng on the PD activity level me easured), whe ere this is forr MV PILC ca able systems s many years. This info ormation sho ows why in XLPE X cable ssystems a qu uick replacem ment of a PD D generating defect is worth to consider, wh here in case of PILC cab ble systems, quick replace ement is selddomly neede ed. ot showing the As an ap ppetizer, Fig g 1 shows the Weibull plo t failure prrobability (y-aaxis) as a fu unction of time (x-a axis) in case all data for XLPE X and P PILC cables is mixed. It shows s that thhere is a 50% % change on failure e after 3 yea ars (with 90% % confidence bounds it is 1 to 8 years). This time-to-failure information will w help netw work owners s to decide whether w a ccertain PD ge enerating defect sh hould be replaced soon, later or not a at all. Fig 1: Le eft, the failurre probability y as a functio on of time in case the ca able system is not identiffied; right the actua al PD develo opment plot until u failure fo or one the ca ases (blue do ots in the leftt graph). JICABLE15_0156.doc Triple jumps of XLPE insulated HVDC cable development in China: - from 160kV, 200kV to 320kV Shuhong XIE (1), Mingli FU (2), Yi YIN (3 1 - Zhongtian Technology Group Co., Ltd, Nantong(China), Xiesh@chinaztt.com 2 - China South Power Grid International Co., Ltd, Guangzhou(China), fuml@csg.cn 3 - Shanghai Jiao Tong University, Shanghai (China), yiny@sjtu.edu.cn HVDC transmission technology has been well recognized due to its significant advantages over the HVAC in terms of transmission capacity, transmission distance and transmission losses. With the technology advancement of VSC (Voltage Sourced Converter) and engineering application, research and development on HVDC cable has been initiated since 2012 because of the first industry application including the research of the insulation materials , design, manufacture and tests of DC submarine power cable and factory joint and cable accessories as well. Under the specification of TICW (National Quality Supervision and Inspection Center of Wire and Cable) for DC power cable, Zhongtian Technology (ZTT) as a pioneer in China has succeeded in ±160kV, ±200kV and ±320kV DC power cables for domestic and oversea commodity market. In December 2013, ±160kV DC submarine and land cable with a total length of 37 km was put into operation in a three-terminal VSC DC transmission project for the connection of Nan’ao island wind farm to the onshore grid of China Southern Power Grid. In June 2014, 294 km ±200kV DC submarine power cable also came into service in Zhoushan multi-terminal VSC DC transmission project owned by State Grid . Another VSC project at the voltage level of ±320kV is under construction in Xiamen within State Grid of China, in which a cable with the length of 21 km will be deployed and the relevant prequalification test is in progress. The project is expected to come into service in October 2015. On the completion of three projects within three years of time China has realized triple leap in its HVDC submarine and land cable development. The paper presents the technical achievement of XLPE insulated HVDC cable development in details of material characterization, space charge behaviour, degassing processing and testing considerations. Their application in three projects is briefed as well to illustrate the insulation and coordination design by considering each individual transmission system. JICABLE15_0157.docx Lightning Impulse test requirement for HVDC transmission systems Henrik JANSSON (1), Thomas WORZYK (1) 1 -ABB AB, High Voltage Cables, Karlskrona, Sweden, henrik.l.jansson@se.abb.com, thomas.worzyk@se.abb.com To enable the planned production of renewable energy according to EU:s energy policy objectives development of the national grids is necessary. Due to challenges of getting permissions for overhead lines, the need of more environmental friendly ways of transmitting electrical power on land have increased which have resulted in transmission systems where overhead lines are combined with underground cable. Transmission systems consisting of overhead lines are exposed to lightning strikes. When cables are a part of the system, the cable system will also be exposed to lightning strikes. For AC transmission systems, relevant standards specify test voltage levels for lightning impulse, but for DC systems the relevant standards specify that the cable system should be tested at voltage levels corresponding to the conditions of the specific project. In order to establish such test voltage levels studies on the overvoltages in mixed DC transmission systems after a lightning strike have been conducted. The studies conclude that general statements on test voltages, related to the rated voltage, cannot be given. The studies show that the overvoltages may be significantly different both in terms of voltage level and polarity from what is commonly seen in specifications of HVDC cable projects. The lighting impulse overvoltages of a HVDC system are dependent on project specific parameters such as region specific ground flash density, overhead line tower configuration, grounding conditions and surge reflections at the transition point between overhead line and cables. The studies also conclude that it may be relevant with different lightning impulse test requirements in different part of the system due to attenuation of the surge along the cable. In order to get relevant lightning impulse test requirement of a HVDC transmission system, a project specific study is required to establish relevant type test parameters. Even during the planning phase of a transmission system project, simulations may give relevant result for specifying test voltages to use for contract preparation. JICABLE15_0158.doc Development of termination for HTS cable. Kazuhisa ADACHI, Kiyoshi HENMI, Tatsuhisa NAKANISHI, Nobuhiro MIDO, Nobuyuki SEMA, Takayo HASEGAWA (1) 1 : SWCC Showa Cable Systems Co.Ltd, 4-1-1 Minami-hashimoto, chuo-ku, Sagamihara-city, Kanagawa-pref, JAPAN, 252-0253. k.adachi034@cs.swcc.co.jp We (Showa Cable Systems Co. Ltd) have developed HTS cable using YBCO tapes. As for HTS cable, termination is an important key technology for not only an electrical component, but also cryo-system. In order to reduce heat penetration to the cable system, compactness of the termination is necessary. From the point of view, we designed/manufactured a termination rated 35kV, 70MA class, and tested considering IEC recommendation. At first, we designed the dimension of stress relief cone based on the electrical stress, and verified the performance by withstand voltage test of model cable in sub-cooled liquid N2. The connection between YBCO tapes and cupper connector was carried out by soldering and very low resistance was successfully obtained. We used a rubber material for the insulation of the high voltage lead part to relax the thermal contraction. The test results indicated that the bushing had sufficient electrical properties under liquid nitrogen cooling conditions. In order to reduce heat penetration, the termination was assembled by a stainless-double-pipe structure and connected with the superconducting cable installed in a double-corrugated pipe having a heat insulating material in between the corrugated walls. Vacuum treatment was performed to them to make vacuum insulation condition. The heat penetration from the termination, cable, and high-voltage lead was estimated to 200W from the computer simulation. And we produced a cable system using the designed termination, the high voltage lead, and cable, and tested according to IEC recommendation. The test results will be reported in the presentation. Key wordsSuper-conductor, HTS cable, termination JICABLE15_0159.docx Smart Cable Guard - a tool for on-line monitoring and location of PD’s and faults in MV cables economical drivers Fred STEENNIS (1), Martijn VAN HUIJKELOM (2), Frank VAN MINNEN (3), Pascal BLEEKER (4) 1 - DNV GL, Arnhem, the Netherlands, fred.steennis@dnvgl.com 2 - Enexis, Arnhem, the Netherlands, martijn.waf.van.huijkelom@enexis.nl 3 - Alliander, Arnhem, the Netherlands, frank.van.minnen@alliander.com 4 - Locamation, Enschede, the Netherlands, pascal.bleeker@locamation.nl For several years Smart Cable Guard (SCG) has proven to be an effective monitoring instrument for diagnosing MV underground power cables. Apart from its ability to detect and locate PD generating defects, since 2014, it is also possible to detect and locate faults in a MV underground power cable network. The failure location information will become available within a few minutes after the actual failure. The fact that with SCG network owners are able: to prevent failures by detecting and locating PD generating defects (assuming a repair) with 1% location accuracy to more quickly repair a fault by detecting and locating faults with 1% location accuracy, information being available within 5 minutes after faults appear helps the network owners to make the network more reliable, both from a SAIDI as well as SAIFI point of view.. This paper discusses the economic aspects of the application of SCG. Some of the more important elements in this analysis are: total cable length and length of MV cable that can be guarded with SCG total number of customers network characteristics with respect to the types of cables and accessories, the number of failures per year and type of grounding, etc. efficiency of SCG to locate PD generating defects efficiency of SCG to locate faults costs for the hardware and monitoring with SCG costs for the installation and maintenance costs for repair of a defective spot in case of a traditional defect or fault and in case of a defect or fault found with SCG costs for data communication Based on this information in this paper it will be shown how SCG can be used to reduce SAIDI and SAIFI in a cost effective way. JICABLE E15_0160.do ocx und power ca ables - return n of experien nce Failures in undergrou AN MAANEN (1), Corne elis PLET (1) , Peter VAN DER WIELE EN (1), Sandder MEIJER (1), Bernd VA Frankk DE WILD (1) ( and Fred STEENNIS (1) 1 - DNV GL, Arnhem m, the Netherrlands, bernd d.vanmaanen n@dnvgl.com m, cornelis.p plet@dnvgl.com, peter.va anderwielen@ @dnvgl.com,, sande er.meijer@dnvgl.com, fra ank.dewild@ @dnvgl.com, fred.steennis f s@dnvgl.com m For man ny years alre eady, DNV GL’s G branch on operation nal excellenc ce (formerly known as KEMA), K is performing failure an nalyses on all a types of power equip pment. On a regular bassis also und derground power ca ables are being investiga ated after havving failed. An A investigation is normaally focused on o finding the root cause, but behind b this ro oot cause find ding, there are a drivers as s avoiding futu ure failures by b a o having a better design, d produ uction, installation, testing g or service circumstances o tracing back which other com mponents mig ght suffer fro om the samee problem and have to be replaced r (in order to prrevent outag ges and rela ated safety problems, costs c and repu utation issues s) iidentification n of the party y that is respo onsible for th he root cause e of the failurre. Failures as mentione ed above, can be a full breakdown,, but can als so be a defeect, like a vo oid in the insulation material ass shown in Figure F 1. In this pa aper, commo on experienc ce as obtaine ed by DNV GL G with failure analyses over the ma any years will be sh hared with th he reader. It will w focus on n the following questions: w when did th he failure ha appen: durin ng testing off tthe design, the produc ction, the insstallation orr d during servicce operation? ? w which com mponents did d fail: ca able, joint, ttermination or o others? w what are the e voltage cla asses involvved: LV, MV, HV or EHV? w what are the e cable type es involved: land cable, ssubmarine cable, c AC cable, c DC ccable, paperr iinsulated cab ble, extruded d cable, …. e etc.? w what are the e most com mmon root ca auses? This s w will be treatted only for cases in w which is nott p possible to link a spec cific failure tto a certain ccable manuffacturer, netw work owner o or other third p party. The fina al aim of this paper is to proviide concise e information, based d on the described return off experien nce, to netwo ork owners, cable c manufa acturers and third parties like installation co ompanies wo orld-wide to o avoid similar mista akes leading g to a redu uced failure e probabiliity and thuss increased reliability o of the cable e system. Figure 1 - void in the insulation material m of an extrude ed HV cablee, causing inttense PD activity du uring the facto tory acceptan nce test. JICABLE15_0161.doc Measurement of the conductor temperature in power cable production Henning FRECHEN (1), Gregor BRAMMER (2), Ralf PUFFER (1), Armin SCHNETTLER (1) 1 - RWTH Aachen University, Aachen, Germany, frechen@ifht.rwth-aachen.de, puffer@ifht.rwthaachen.de, schnettler@ifht.rwth-aachen.de 2 - Forschungsgemeinschaft für Elektrische Anlagen und Stromwirtschaft e.V., Mannheim, Germany, Gregor.Brammer@fgh-ma.de To ensure a cost-efficient operation and a long lifetime of a power cable, high requirements to the production quality have to be met. During the production of the insulation system, the cable core including the conductor is heated up to activate the cross-linking agents. Due to the high thermal conductivity of the metallic conductor, which is still partly in the CV-line, the cable core may be reheated from the inside during cooling in the water bath. This reheating process can lead to a degradation of the mechanical stability, which is critical for the spooling of the core onto the drum. Hence, the production speed has to be reduced to ensure sufficient cooling and to eliminate the appearance of critical temperatures. State-of-the-art line control systems estimate the conductor temperature by calculation, which is sensitive to a variety of physical input parameters. A verification of the temperature estimation via measurement does not exist. Therefore, a method to measure the conductor temperature is desired to avoid scrap production due to undetected faults. In previous works a fundamental method for the measurement of the conductor temperature using ultrasonic technique has been developed (1). The method is based on the evaluation of the reflected ultrasound impulse at the interface between the insulation layer and the inner semiconducting layer. The reflected signal is analyzed by means of amplitude and frequency. Using lookup tables and models for acoustical parameters and cable design, a temperature measurement on a medium voltage (MV) cable with a precision of +/- 2°C could be achieved. 300 Transducer Temperature 52°C Temperature 64°C Temperature 76°C Temperature 90°C 250 Outer Semicon XLPE Inner Semicon Conductor Amplitude in a.u. Pos 5 Pos 15 In this article, different influencing factors on the temperature monitoring method are investigated. Ultrasonic Measurements on medium and high voltage cable cores with solid and stranded conductors are performed. The previous results were achieved on a MV cable with a fixed transducer position in relation to the cable core. Due to the movement of the core during the production the reflected ultrasonic signal will change depending on the conductor design. The results confirm the dependency of the ultrasonic measurement on the transducer position (Fig. 1). Single wires of a 150 mm² stranded conductor are detected in a MV cable and the position with the highest amplitude is automatically chosen for the temperature measurement. 200 150 100 50 0 0 5 10 15 20 Transducer position in mm 25 30 Fig. 1: Test setup with adjustable transducer position (left) and dependency of ultrasonic amplitude on transducer position (right) Furthermore, the ultrasonic measurement is dependent on the insulation layer thickness of the cable core due to the sound attenuation in XLPE. So, in a high voltage cable the effect of higher sound attenuation cannot be neglected for a temperature measurement of the conductor. A compensation model is developed to consider the different dimensions of MV and HV cables. 1 - G. Brammer, “Kontaktlose Messung der Leitertemperatur in der Energiekabelproduktion mittels Ultraschall”, Dissertation, RWTH Aachen University, Germany, 2013 JICABLE E15_0162.do ocx ection and ac ccurate location of faults ((full breakdo owns) in Smart Cable Guard - introducing on-line dete MV ccables Paul WA AGENAARS (1), Tjeerd BROERSMA B A (2), Denny HARMSEN (3), Pascal B BLEEKER (4 4), Fred STEE ENNIS (5) 1 - DNV GL, Arnhem m, the Netherrlands, paul.w wagenaars@ @dnvgl.com 2 - Enexxis, Arnhem, the Netherla ands, tjeerd.b broersma@e enexis.nl 3 - Allian nder, Arnhem m, the Netherrlands, dennyy.harmsen@ @alliander.com 4 - Locamation, Enscchede, the Netherlands, N pascal.bleek ker@locamattion.nl 5 - DNV GL, Arnhem m, the Netherrlands, fred.ssteennis@dn nvgl.com For seve eral years Sm mart Cable Guard G (SCG G) has proven n to be an effective monnitoring instru ument for diagnosiing MV unde erground pow wer cables. P Partial discha arges (PD’s) from weak sspots can be detected and loca ated, both continuously and on-line (ssee the Fig 1). Since 20 014, it is alsso possible to detect an nd accurately locate fau ults in a MV V cable netw work. This w minutes after information will beco ome available e within a few a the failure. This will help DNO’s to speed up their repair work. Different frrom most prrotection equ SCG has standard a uipment for MV M cables, S time syn nc on board. With that, th he first trave elling wave frrom a fault arriving a at booth sides of the t cable etected, givin will be de ng accurate location posssibilities (like e with PD’s, also a for faults ts it is 1% of the cable length). But there arre more adv vantages of detecting faults in this way. w A traveelling wave is i always there, independent on o the system grounding g or type of fault. f It also doesn't mattter whether a fault is being sw witched off or not by the protection e equipment, it has already y been locateed by SCG. Even the resistancce of fault, hiigh or low Oh hmic, doesn’’t matter. SCG hass been deve eloped in coo operation witth Dutch netw work owners s and Locam mation. These e network owners (Enexis and d Alliander) represent a about 60.000 km of MV V undergrouund cable. It is their experien nce with SCG G that will be discussed in n the paper. Apart fro om summarizzing shortly SCG’s abilityy to detect and a locate PD related deefects, a larg ge part of the pape er will treat th he new fault detection an nd location fe eature of SCG. For this, practical exa amples of faults de etected in rea al life will be incorporated d. Fig 1: PD D activity me easured by SCG S as a fun nction of time e (x-axis: cab ble length; y--axis: time; z-axis: PD intensityy) JICABLE15_0163.doc Behaviors of Water Tree Propagation After Accelerated Aging Under Different Polarity DC Voltages Kai ZHOU, Tianhua LI, Mingliang YANG, Ming HUANG, Kangle LI 1 - School of Electrical Engineering and Information, Sichuan University, Chengdu, Sichuan, China, zhoukai_scu@163.com, lier_tiantian@126.com, mlyang1029@163.com, hm_scu@163.com, likangle109@126.com HVDC XLPE cables have been widely used in new energy power generation, power supply dilatation in cities and island power transmission. Even though water trees under DC voltage propagate much slower than those under AC voltage, water-tree propagation under DC voltage can be accelerated in the presence of harmonics generated by non-linear converters. Different voltage polarity in bipolar HVDC systems can affect the space charge distribution and ion diffusion activity in XLPE insulation, which can further result in different growth characteristics of water trees. To investigate the influence of DC voltage polarity on propagation behaviors of water trees in the presence of harmonics, water-tree growth behaviors in XLPE material were investigated by utilizing four rectified voltage waveforms (e.g., positive polarity half-wave and full-wave voltages, negative polarity half-wave and full-wave voltages) and a standard sinusoidal voltage waveform. A water-tree accelerated aging experiment was performed on XLPE samples under the five different voltages respectively. An optical microscope was used to observe water-tree morphologies in the samples, and sizes of the water trees were also counted after 22 days of aging experiment. Experimental results show that the morphologies and the sizes of water trees are strongly dependent on DC voltage polarity. Water trees under the positive polarity voltages are significantly shorter than those under the negative polarity voltages. Meanwhile, water-tree branches under the positive polarity voltages are more transparent and thinner than those under the negative polarity voltages. According to the results, a possible mechanism based on different ion diffusion activity is proposed. The diffusion of hydrated ions in the material plays an important role during the process of water-tree aging. The flux of ions is different under different voltage polarity. As a result, the numbers of water molecules driven into the polymer are different, which can result in the difference of water-tree propagation characteristics. Key words XLPE; cables; water treeing; DC voltage; polarity; ion diffusion JICABLE15_0164.doc Condition of shielded 5kV pink EPR insulated cables after 25 years of service in wet environment Bogdan FRYSZCZYN (1), Andrew MANTEY (2) 1 - Cable Technology Laboratories, Inc., 625 Jersey Avenue, New Brunswick, NJ 08903 USA, bogdanf@cabtl.com 2 - EPRI 1300 West WT Harris Boulevard, Charlotte, NC 28221, USA amantey@epri.com There are 100 nuclear power reactors generating 20% of total U.S. electric energy. The average age of the nuclear reactors is about 33 years old. Shielded medium voltage (5kV and 15kV) cables in these plants are insulated with butyl rubber (3%), black EPR (38%), XLPE (13%), brown EPR (13%) and pink EPR (32%), introduced commercially in 1974. The pink EPR insulation delivers much more reliable service than its predecessor, black EPR, but as with other polymeric insulation, pink EPR is not immune to aging in wet environments, contrary to manufacturer’s marketing. Because of their age the MV cable failures are of great concern, as such events quite often lead to unplanned plant outages costing approximately 1.5 million U.S. dollars per day in lost revenues. Much of the past research focused on XLPE insulations, but EPR’s comprise the majority of cables in power plants and has been the focus of EPRI sponsored research at Cable Technology Laboratories since 2006. The paper will describe the condition of two 3/c cables removed from nuclear plants because of their high and unstable values of 0.1 Hz dissipation factor of one of their phases. The cables were replaced and the removed cables were subjected to laboratory forensic evaluation. It will be shown that water treeing is responsible for the substantially decreased cable insulation strength. This research also shows that very advanced water trees, spanning nearly the entire insulation wall are detected by 0.1 Hz tangent delta measurements. The ac breakdown strength of such cable insulation in five-minute ac step voltage test has to be 4kV/mm or less, while its average operating stress of the cable is about 1kV/mm. The initial ac strength of pink EPR insulation of the cable was about 28kV/mm. Insulation Shield Conductor Shield Photomicrograph of the surface of a pink EPR, cross-cut, insulation wafer at the location of AC break down. Bow-tie type water tree spans the whole insulation wall (3.8 mm) from conductor shield to insulation shield. JICABLE15_0165.docx Influence on measured conductor AC resistance of high voltage cables when the shield is used as return conductor Marcus HÖGÅS (1), Karl-Erik RYDLER (1) 1 - SP Technical Research Institute of Sweden, Borås, Sweden, Marcus.Hogas@sp.se, karlerik.rydler@sp.se The CIGRE Working Group B1.03 recommends that the AC resistance of large cable conductors should be measured when the cable designs are being type tested [1]. In line with this a measuring system of conductor AC resistance of high voltage AC cables was presented at the Jicable’11 conference [2]. In this method the AC resistance is measured using a low current and the shield of the cable as the return conductor, to minimize the inductance of the circuit. However, it has been questioned if the current in the shield induces additional power losses in the conductor due to eddy currents which will influence the measured AC resistance. This question is particularly relevant in the common case where the wires of the shield are wound, where the analogy with an ideal coaxial cable with a solid shield is not applicable. In order to estimate the induced power losses in the conductor due to the magnetic field generated by the current in the shield wires we utilize an iterative method based on Maxwell’s equations. According to this method the first order estimation of the induced current in the conductor is described by , , , (1) is the absolute value of the induced current where we have used cylindrical coordinates , , is the angular density, is the angular frequency, is the conductivity of the inner conductor, and component of the magnetic flux density. Here we are only interested in the order of the induced power losses and not in a precise value so making a first order approximation (i.e. taking the first step in the iteration) is sufficient. Using (1) and considering the different possibilities of the geometry of the shield (i.e. if the shield wires are laid straight or are wound) one can show that the induced power losses in the conductor due to the current in the shield decreases exponentially with increasing number of wires in the shield. The exponential decrease is faster when the wires are laid straight compared with wound wires. For a typical high voltage cable the induced power losses due to current in the shield is below ppm-level compared to the self-induced power losses of the conductor. Thus, using the shield as the return conductor will have negligible influence on the measured conductor AC resistance. Further details will be provided in the full paper. References [1] CIGRE Working Group B1.03, 2005, Large cross-sections and composite screens design, Electra Technical Brochure 272 [2] K.-E. Rydler, M. Sjöberg and J. Svahn, “A measuring system of conductor AC and DC resistance,” Jicable’11, Versailles, France, A.8.1, June 2011. JICABLE15_0166.doc On line diagnosis experimentations for MV cables in ERDF distribution network. Hervé DIGARD (1), Roger TAMBRUN (2) 1 : EDF Lab - Les Renardières, Ecuelles, 77818 Moret sur loing, France herve.digard@edf.fr 2 : ERDF Direction réseau - 102 terrasse Boieldieu - 92085 Paris la défense CEDEX, France roger.tambrun@erdfdistribution.fr Since 2012 ERDF experiments on line diagnosis systems for its MV underground cables distribution network. Four diagnosis systems have been installed in 4 source substations in order to record the different transients which affect the network and to identify among them the "pre-faults" also known as "self extinguishing" single phase faults. The specific diagnosis systems have been designed to record power frequency phenomenon but also high frequency phenomenon in order to investigate solutions for the localization of the pre-fault on the underground cable network. The high number of measurements taken from the diagnostic systems permitted to analyze many prefaults and faults records and to establish correlations between some self extinguishing faults and persistent faults. The final goal of the on line diagnostic system is the prevention of future failures. In order to reach that objective, the fault location has to be performed. Thanks to the high sampling rate of the data acquisition systems, locations of fault have been done successfully in some cases using the high frequency records of cable screen currents measurement. The return of experience of these investigations and the help of simulation showed that the fault location still remain a challenge with long cable lengths, the presence of cable derivation and the variation of the fault resistance. a) b) On site measurements of cable screen currents vs time on a faulty feeder a) b) Cable screen current measured on a single phase "self extinguishing fault". Same cable screen current measured one month later on a persistent cable fault. Key words : On line diagnosis; self extinguishing faults; faults location. JICABLE15_0167.doc Influence factors of field inversion in HVDC cables Karsten FUCHS (1), Andreas FISCHER (2), Dietmar DRUMMER (2), Frank BERGER (1) 1 : Ilmenau University of Technology, Gustav-Kirchhoff-Straße 1, Ilmenau, Germany karsten.fuchs@tu-ilmenau.de, frank.berger@tu-ilmenau.de 2 : Institute of Polymer Technologie Friedrich-Alexander-Universität Erlangen-Nürnberg, Am Weichselgarten 9, Erlangen, Germany fischer@lkt.uni-erlangen.de, drummer@lkt.uni-erlangen.de In HVDC cables an electric flow field is reached in steady state, which depends on the joule heating effect of the inner conductor and the resulting temperature-dependent electrical conductivity of the insulation material. As a result the effect of field inversion is caused by a reversal and increasing of the electrical field strength in the insulation material to the outer conductor and limits maximum loads of HVDC cables. The focus concentrates on target manipulations of the thermal conductivity of insulation materials to minimize the effect of field inversion. To establish a basis the influence of temperature and voltage will be shown on the resulting electrical field strength in used cross linked polyethylene (XPLE). Possible distributions, which are reached by typical rated voltages and currents, will be demonstrated on the basis of numeric analysis. The effect of thermal conductivity will be investigated basically by measurements of temperature, dielectric strength and electrical conductivity as well as numerical simulations with conductive polymers. These investigations could effect that the load of HVDC cables can be raised for further applications. Key words HVDC cables; Field inversion; New materials; Thermal conductivity JICABLE E15_0168.do ocx Estim mating the losses in th hree corre subm marine p power cables c using g 2D and d 3D FEA simullations Sebastia an STURM (1 1), Frank BE ERGER (2), JJohannes PA AULUS (1), Karl-Ludwig K A ABKEN (3) 1 - Unive ersity of Applied Sciences Würzburg--Schweinfurt, Schweinfurrt, Germany, Seba astian.Sturm@ @fhws.de, Jo ohannes.Pau ulus@fhws.d de 2 - Ilmen nau Universitty of Technology, Ilmena u, Germany,, Frank.Berger@tu-ilmennau.de 3 - Nordd deutsche Se eekabelwerke e GmbH /Ge eneral Cable, Nordenham m, Germany, Karl-L Ludwig.Abke en@nsw.com m Several recent publications hav ve described d and discus ssed the losses in the aarmour of th hree core submarin ne power ca ables; espec cially in the ccase of large er cables, th he losses seeem to be lo ower than estimate ed with the IE EC 60287 sta andard. Thereforre, this paper further inve estigates the e losses in co onductors, shields, and aarmour on th hree core submarin ne power ca ables utilizin ng a comme ercial FEA to ool. Models were set u p using the Maxwell equation ns to calcula ate the joule e losses in conductors and losses s caused byy induced circulating c currents as well as eddy curre ents in surro ounding metallic compon nents. 3D m models were used to estimate e the reductio on of circulatting currents in the armou ur because of o different pparameters (lay length and/or la ay direction) applicable for f core stran nding and arrmouring. Fu urthermore thhe expressiv veness of correspo onding 2D models m can be evaluatted. With th he verified 2D models further ana alyses of parametters influenciing the losse es in cables e.g. the ma agnetic perm meability, elecctric conductivity and contact p points betwe een armour wires w were pe erformed. A compa arison was made m of the simulated s lossses in the cable c models s against the losses acco ording the standard d. An overvie ew of the los sses in armou ur, shield an nd conductors is given. T The results id dentify an interactio on of lossess in the com mponents an d it can be summarized d that the suum of the calculated c losses by FEA is con nsiderably low wer than the e respective IEC 60287 ca alculation ressult. Fig. 1:.2D and a 3D FEM M models of submarine s po ower cables Keyword ds: IEC 6028 87-1-1; armou ur losses; thrree core sub bmarine powe er cable; FEM M/FEA JICABLE15_0169.docx REE’s Research and Development projects related to predictive maintenance based on monitoring of critical parameters in high voltage underground cables. Gonzalo DONOSO (1), Ricardo REINOSO (1), Rafael GARCÍA (1), Luis Felipe ALVARADO (1), Javier ORTEGO (2), Luigi TESTA (3) 1 - Red Eléctrica de España, Madrid, Spain, gdonoso@ree.es , rreinoso@ree.es , rafgarcia@ree.es , lalvarado@ree.es 2 - DIAEL, Madrid, Spain, javier.ortego@diael.com 3 - Prysmian Cables and Systems, Barcelona, Spain, luigi.testa@prysmiangroup.com In order to increase the useful life of underground circuits, it is very important to identify (and monitor, if possible) the critical elements and parameters of the installations, so their condition can be controlled. Two different projects have been developed, within the REE Research and Development policy, in order to achieve the target of online monitoring two different critical parameters related to underground lines: partial discharges and sheath currents. The project of online monitoring of partial discharges (PD) was the result of an association between REE and DIAEL (High Voltage Electrical Insulation Diagnosis). This system has been installed in an underground cable system of the electricity transmission network in the metropolitan area of Madrid. This pilot R&D initiative will allow us to know the insulation behavior of underground cable systems under different network conditions and external factors that could affect their integrity. The monitoring system employs PD measuring units placed in the cable system accessories (terminations and joints). Each PD measuring unit has HFCT sensors installed around the ground connection cables of the accessories and communicates with the other units and with a control and analysis unit by fiber optic links. The data acquisition is synchronized and sent to control and analysis unit for analysis. The system includes a software tool to discriminate between PD pulses and noise signals, to determine the PD measurement sensitivity, to identify and locate existing PD sources and to analyze the correlation between each PD source and its associated defect. The project of online monitoring of sheath currents (SC) was the result of an association between REE and Prysmian Cables and Systems. The underground line chosen for the pilot project is located near Madrid. It is composed of two parallel circuits with different bonding connections of the cable sheaths in the joint bays (cross-bonding and single point) and in the terminations (one end has GIS terminations located in a substation and the other one has outdoor terminations at a transition tower). The monitoring system is composed of a distributed network of devices called nodes, which communicate among them and with a local modem via radio, sending the data continuously (SC values and other information) to a distant computer. Different autonomous power generation systems have been tested (i.e. solar cells and induction current transformers) to supply the local modems. Finally, data are stored and managed in a central server that can be accessed online by a web interface with several management features. Real-time alarms can be activated when the measured parameters exceed the established thresholds. The added value of these projects consists in making possible to assess the current condition of the installation by means of continuous online monitoring. Through proper analysis of these values it is possible to design a behavior model of any given circuit with specific features. As a result, maintenance design plans are more adequately adapted to reality. JICABLE15_0170.doc Design studies for French submarine links Nathalie BOUDINET, Jean CHARVET, Matthieu DORY, Emmanuelle LAURE, Vincent MOINDROT, Frédéric LESUR 1 - RTE, Paris, France, nathalie.boudinet@rte-france.com, jean.charvet@rte-france.com, matthieu.dory@rte-france.com, emmanuelle.laure@rte-france.com, vincent.moindrot@rte-france.com, frederic.lesur@rtefrance.com. RTE will develop in the next years several submarine links, HVAC and HVDC: Already two calls for tender have been launched by the French energy regulation commission to develop the offshore wind farms along the French coast. RTE is responsible for the building, operation and maintenance of the HVAC export cables (6 power plants of 500 MW each are to be connected between 2018 and 2023). A new interconnection with England is foreseen to be built by 2020, this interconnection will be an HVDC link An HVDC link in south-east of France is foreseen to be built by 2021, this national connection will run along the Mediterranean coast by the sea. Further projects of submarine links are listed in the 10-year development plan of RTE. RTE is carrying out design studies in order to define the best technico-economical features of these future links (AC or DC, number of links, voltage level, current rating, etc.). Design criteria are numerous and this paper focuses especially on: The design criteria in regards to the state-of-the-art of submarine cables technologies, The design criteria at the landfall part, which is the thermal bottleneck of the submarine. Regarding the first bullet, technico-economical studies have been conducted to define the technological choice of each submarine link, taking into account the state-of-the-art of the HVAC and HVDC submarine cable technologies. The present paper explains the different results obtained. RTE has performed many engineering studies for these links and some studies are still on-going. For the landfall part, the paper describes the main issues and how RTE imagines handling those regarding thermal aspects and installation: Feasibility of the installation in trench or HDD Fault containment Pulling efforts Thermal resistivity of soil Burial depth Cable characteristics and calculation methods Correlation with electro-technical studies (reactive power management for HVAC links for instance) JICABLE E15_0171.do ocx Valida ating and qua antifying g reliability imp provem ents off new cable e design ns - a ca ase stud dy of 600 0 v self sealing s cables Chris FL LETCHER (1), Joe Mc AU ULIFFE (2), & Joshua PE ERKEL (3) 1 - Duke e Energy, Charlotte, USA A, Chris.Fletccher@duke-e energy.com 2 - South hwire, Carrollton, USA, Jo oe.McAuliffe@ @southwire..com 3 - NEET TRAC, Atlanta, USA, jos shua.perkel@ @neetrac.gattech.edu Manufaccturers continue to mak ke and utilitties continue e to deploy new cable designs to address importan nt technical and a reliability y problems. These new solutions are e tested in thhe laboratory y through developm ment and ap pproval tests s. Although tthe deploym ment begins only when aall of these tests are complete ed to the sattisfaction of all involved; there is still a need to verify v that thee solution re eally does address the problem m and does not n introduce other unfore eseen issues s. This need exists becau use there me very impo ortant differences betwee en laboratory y tests and field experieence; laborattory tests are som are dessigned to de eliver consis stency and repeatability, service experience e increases the scale (generally by length of product) and a exposess the solution n to the ill-de efined rigors of service. However, H although h absolutely essential, e mo onitoring perf rformance in service is a challenging undertaking.. Classica ally, the servvice performa ance challen nge would be b addressed d by selectinng an area of o known problemss and constrructing a gro oup with the new solution and a group without thhe new solution - the control p population. The T performa ance would b be monitored d for a suitab ble period of time until a clear c and verifiable e difference could be discerned. Un nfortunately for f new cable solutions this approach is not feasible for a number of reasons: ping is often not robust en nough to seg gregate the inputs from thhe mixed Co ontrol and Record keep New populattions Installation needs n to be part of the normal operration of the utility such that stock & training vvariables do not interfere e C Confirmation n Bias (an ab initio perce eption of go ood or poor performance p e) can overw whelm the d desired signa al O Once the efffectiveness of o the new ssolution is co onfirmed upgrading the ccontrol population can p prove to be a logistical and philosoph hical challeng ge Thus, offten the only practical wa ay forward iss to deploy in n areas and compare perrformance with w a non matched d, non interccalated Conttrol Group. C Consequentlly the analyttical strategiies used ne eed to be sufficiently robust. In n these case es one issue e that becom mes importan nt is the veryy success off the new solution - if it is effecctive then the ere will be a lower incide ence of problems (i.e. wee end up dea aling with will be quan ntized and efffect of any incorrectly attributed a very small numbers) such that the effects w problem will be ampllified (the effe ect of 2 misssed failures in n 100 is sma all compared to 2 missed in 15). A case c study was underttaken on th he Duke Enerrgy system using their 6600 V cable e system. The final connection bbetween re esidential custo omers and d the prrimary und derground distrribution system is madee using low w voltage (600 0 V) unsh hielded cabbles (often termed “secondary” cables). These low voltage systems can often be damaged d duuring or so oon after insta allation as bu uilders and laandscapers complete theirr construction work. Som metimes this damage lts in an imm resu mediate failur re (dig in) while other Figure 5: Corrosion Failure times the insula ation is just damaged enough to n of the cond oisture ingresss and eventtual corrosion ductor (Figurre 5). allow mo JICABLE E15_0171.do ocx manufacturerrs have ap pproached t his Cable m problem in a coup ple of ways s: (1) tough her insulation materialss and (2) self-sealiing insulation (Figure 6)). The exam mple studied in this pa aper involves the transition fro om traditiona al 600 V insulations to a self-sealiing insulation. This pap per will discuss an effec ctive analyticcal solution using the e Crow / AMSAA Figure 6: Self-Sealing S g Cable methodo ology using the seconda ary cable case study from Dukke Energy. In n particular th he paper will describe: (1) (2) (3) (4) (5) Issues faced d in verifying new cable ssolutions C Crow-AMSA AA technique for Performa ance Evaluattion O Overview of Low Voltage e (600 V) Cab ble Designs W Why Low Vo oltage Cable Systems Fa il? Results of Duke Energy Case Study a. Data a from multi-y year pilot stu udy b. Initia al performance prediction ns c. Com mparison of predicted p perrformance to actual performance in seervice (6) T The benefitss in more ra apid uptake of new tec chnology witth and effecctive way to quantify b benefits JICABLE15_0172.docx Modeling of DC cables for transient studies Minh NGUYEN TUAN (1), Alain XEMARD (2), Quentin WOLFF (3) 1 - EDF R&D, Moret-sur-Loing, France, minh-2.nguyen-tuan@edf.fr 2 - EDF R&D, Clamart, France, alain.xemard@edf.fr 3 - EDF CIST, Saint-Denis, France, quentin.wolff@edf.fr The electrical modeling of AC underground single-core cables is a topic that has been quite well addressed. Accurate models are available and suitable for steady-state as well as transients studies. The development of DC systems goes along with an increasing demand for electromagnetic transient simulations involving DC cables. These are generally represented by simple models or AC cable models. As a result, physical phenomena proper to DC cables are omitted, which may be detrimental to calculations accuracy. In AC cables, dipoles generation and orientation phenomena occur with time constants much shorter than one power frequency period; space charges migration are only of secondary importance. Therefore, the electric field inside the insulation can easily be calculated, assuming that the charge density is nil. On the other hand, in DC cables, these phenomena cannot be ignored, for they lead to a non-zero charge density inside the insulation. It is then considered that the insulation conductivity varies with temperature and electric field. This makes the computation of the latter much more difficult. To model a transmission line is to derive the telegrapher’s equations, which govern voltages and currents in conductors, from Maxwell’s equations, which describe the propagation of the electromagnetic field. This is what is behind the models commonly used in EMTP-like programs. Can these models be used to represent DC cables? In this paper, the impact of a temperature and field dependent conductivity on the telegrapher’s equations is studied, starting from Maxwell’s equations. It is shown that in this case, the telegrapher’s equations cannot be solved as they currently are in EMTP. However, it seems still acceptable to use the existing models for transient studies, if the following changes are carried out: Adding a voltage source to the model to represent the electric field due to space charges; Modification of the admittance matrix to reflect the inhomogeneity of the conductivity. This approach contributes to enhance the accuracy of DC cable modeling, without requiring deep changes in the EMTP code. JICABLE15_0173.doc Main objectives and results of the European project ADVANCE (Aging Diagnostics and Prognostics of low voltage I&C cables) Christophe MOREAU (1), Maud FRANCHET (1), Davide FABIANI (2), Luca VERARDI (2), Sandrine FRANCOIS (3) 1 - EDF R&D, Moret sur Loing, France, christophe.moreau@edf.fr, maud.franchet@edf.fr 2 - UNIBO, Bologna, Italy, davide.fabiani@unibo.it, luca.verardi4@unibo.it 3 - EDF SEPTEN, Villeurbanne, France, sandrine.francois@edf.fr Extending the lifetime of a Nuclear Power Plants (NPPs) to 60 years or more is among one of the most important concerns in the global nuclear industry. As electric cables are one of the long life items that have not been considered for replacement during the design life of NPPs (typically 40 years), assessing their degradation state and predicting their remaining lifetime are very critical issues. This paper presents the main objectives and results of the project ADVANCE. ADVANCE (Aging Diagnostics and Prognostics of low voltage I&C cables) is a 3 years collaborative R&D project co-funded by the European Commission under the Euratom 7th Framework Program in nuclear fission and radiation protection that ended in 2013. It addressed issues regarding the assessment of safety-related cables that are required to operate not only during normal operating conditions but also under accident conditions, like in the case of the Loss Of Coolant Accident (LOCA). The main goals of the project were to: adapt, optimize and assess promising electrical condition monitoring (CM) techniques for nuclear cables that are non-destructive and can be used in the field to determine the current condition of installed cables over their entire length; establish acceptance criteria by correlating physical cables properties to electrical properties in order to evaluate the degree of degradation and to provide information about the cable remaining useful life. Safety-related low voltage power cables, instrumentation cables and control cables representative from those currently employed in European NPPs with different insulations (XLPE, EPR, EVA) have been selected, studied and tested in the project. Cable environmental conditions and function requirements were described as well as accelerated aging protocol for short and long samples. These cables were used in two main test programs. In the first, long cables were aged and different CM techniques were used to track the different stages of aging. In the second, short cables were aged to provide a multi-stress modeling under various aging factors. Investigations carried out on short samples have shown that dielectric spectroscopy is the most promising electrical CM technique among those investigated. Measurements on long samples with promising electrical CM techniques (reflectometry) have been compared to those with more traditional CM techniques. It was difficult to detect a global aging. At the moment reflectometry techniques seem more adapted to local defect detection and evolution rather than global aging monitoring. To conclude, further developments are required to improve measurement techniques and analysis. Guidance and propositions for future work built on the analysis of results are suggested. JICABLE15_0174.doc Connection to MV cable longitudinal aluminium screen First Name TOURCHER (1), Members of Sycabel* (2), TAMBRUN (3) 1 - EDF R&D, Moret sur Loing, France, christophe.tourcher@edf.fr 2 - SYCABEL, Paris, France, www.sycabel.com 3 - ERDF, Paris La Défense, France, roger.tambrun@erdf.fr Since polymeric cables are used in France, medium voltage cables have undergone evolutions, both in the design and in the cross-section conductor range. The last evolution leads to a new cable with reduced insulation thickness (4.5 mm) and with a polyethylene oversheath. Previously, French cables had a PVC oversheath. Screen plates, which allow continuity of the screen of accessories and earth connection, have never been modified since the first edition of the French specification NF C 33-014. Fig. 1: three models of screen plate A Working Group Users/Customer has been created within the French Standardization National Committee (AFNOR/UTE TC20) in order to : 1. Withdraw the 10 Amps limitation and validate the maximum allowable current into screen plate in continuous operation, 2. Improve the installation of the screen plate on cables, 3. Make clear the technical definition of the screen plate, 4. Review the national specification NF C 33-014 to take into account new results and conclusions. To study the effects of different parameters (sheath material, metal foil thickness, quality of plate and quality of installation), specific endurance tests were realized with two models of screen plate (for cables 240 mm² and 630 mm²). The most important result is the better behavior of the screen plates tested with PE oversheath. But, examinations and conclusions show that the quality of the contact also depends on the installation methods which are used. To improve the quality of contact with PE oversheath, different methods and devices have been studied by the working group. A short investigation test has been realized to select best installation methods. Once selected, these methods are validated by a long duration test based on IEC 61238-1. First results confirm our investigations for several configurations, only with PE oversheath, and a permanent current of 30-35 A could be possible. JICABLE15_0174.doc However, it shall be necessary to improve tools to guaranty these results on the network. * Members of Sycabel : L. BENARD, S. TOGNALI (PRYSMIAN) E.BERTELOODT, E. SIMEON (NEXANS) F. GOUYGOU (SICAME) F. CHARLOT; X. DELAMBRE (TE CONNECTIVITY) JICABLE15_0175.docx Short-term partial discharge monitoring as a diagnostic tool on 400kV XLPE cable Markus HABEL (1 [2014]; 2 [2015]), Frank BUSSE (1), Ditmar MAIHAK (1), Claus KUHN (2), Thorsten SCHRANK (2) 1 - IPH Berlin GmbH, Berlin, Germany, habel@iph.de, busse@iph.de, maihak@iph.de 2 - 50Hertz Transmission GmbH, Berlin, Germany, Markus.Habel@50hertz.com, Claus.Kuhn@50hertz.com, Thorsten.Schrank@50hertz.com The safe and trouble-free energy supply is an important basic requirement of our modern life. Electrical equipments have a calculated lifetime of 30 years and more. They should be subject to regular diagnosis, to detect possible errors or changes in time and to ensure safe operation. This is generally done during commissioning tests (fingerprint) and/or at regular intervals. In addition to many testing methods and diagnostic measurements, monitoring of various parameters is a way to receive important information from the equipment. The monitoring is usually carried out online, but offline is also possible. At high voltage cables in addition to temperature and load current also partial discharges can be measured. There are different concepts and manufacturers of such systems on the market. At IPH another concept was developed, the short-term partial discharge monitoring. This system was successfully tested on a 400kV cable system in the cable tunnel of 50 Hertz in Berlin. A short-term measurement is generally not a big issue. Longer measurements (e.g., more than 24 hours) are usually limited by the power supply. No external power supply was available at the joints in the tunnel, therefore an intelligent and robust solution had to be found. Because all relevant data for an entire week had to be saved (measuring time 24 hours / 7 days) the requirement of storage space is significantly higher than on conventional systems. The raw data provide more evaluation options, if abnormalities were found. Furthermore, the analysis of the data is more extensive than in usual measurements. This paper describes the full measurement method and the technique of distributed, fully synchronous short-term partial discharge monitoring at 5 groups of joints and 2 groups of terminations. Problems, solutions and challenges for the future will be presented. Besides the description of the technology used, first results of the measurements can be shown. JICABLE15_0176.docx Self-healing high voltage electrical insulation materials Cédric LESAINT (1), Øystein HESTAD (1), Sverre HVIDSTEN (1), Wilhelm R. GLOMM (2) 1 - Sintef Energy Research, Trondheim, Norway, cedric.lesaint@sintef.no, Oystein.hestad@sintef.no, sverre.hvidsten@sintef.no. 2 - SINTEF Materials & Chemistry, Trondheim, Norway, Wilhelm.glomm@sintef.no Electrical treeing can be the precursor to catastrophic failure for electrical insulation materials and hence significantly shorten their service lifetime. Considering that damage inside the composites (thermoset insulation materials containing fillers) is difficult to detect and particularly to repair, the ability to self-heal is very attractive, especially in challenging environments. The main purpose of this paper is to present results from electrical testing of a self-healing composite. Such a composite could e.g. be used as the solid electrical insulation in subsea power cable connectors for deep water oil exploitation where repair is very time consuming and costly. The approach presented in this paper for development of self-healing thermoset electrical insulation materials is based on a technology developed by White et al. in 2001, intended to halt mechanical degradation of the material: Microcapsules filled with a monomer (healing agent) are added to the insulation materials (epoxy) prior to casting. When cracks propagate in the material the microcapsules will rapture, releasing liquid healing agent into the crack. The final step of the self-healing process is the polymerization of the monomer, which occurs upon contact with a catalyst added to the epoxy resin. Electrical degradation by electrical treeing has many similarities with mechanical cracking of the material. For a system containing microcapsules, one or more of the branches of the electrical tree will likely break a capsule, thus filling the electrical tree with the liquid monomer. As the tree structure is interconnected, most of the tree structure is likely to be filled. This depends on the partial pressure and viscosity of the monomer and the surface tension of the hollow tubes. The filling itself should extinguish critical discharges, making further growth less likely. Upon polymerization, further development of the electrical tree should halt, or at least be significantly delayed. A series of tests was conducted to study electrical degradation and breakdown of the thermoset insulation with and without microcapsules with monomer (healing agent) including electrical treeing from a metal needle cast in epoxy, electrical treeing from a micro void in epoxy and electrical breakdown voltage testing of the insulation material using Rogowski test objects. The experiments where a needle or a void is used as an initiation site for electrical treeing provide the possibility of studying the inception and propagation of the phenomena using a microscope. This setup was used to study the interaction between the electrical tree and the micro-capsules in situ, and showed the direct attraction of the electrical trees towards the microcapsules. JICABLE15_0177.doc Long term performance of XLPE insulation materials for HVDC cables Virginie ERIKSSON (1), Johan ANDERSSON (1), Villgot ENGLUND (1), Per-Ola HAGSTRAND (1), Anna KONTRO (1), Ulf H. NILSSON (1), Emy SILFVERBERG (1), Annika SMEDBERG (1) 1 - BOREALIS, Stenungsund, Sweden, virginie.eriksson@borealisgroup.com, carljohan.andersson@borealisgroup.com, villgot.englund@borealisgroup.com, per-ola.hagstrand@borealisgroup.com, anna.kontro@borealisgroup.com, ulf.nilsson@borealisgroup.com, emy.silfverberg@borealisgroup.com, annika.smedberg@borealisgroup.com, The dielectric of the cable will be exposed to small amounts of oxygen during the manufacturing steps and its operation. This requires that the materials are properly stabilised against the thermo-oxidative ageing as otherwise the morphology and the chemical structure of the XLPE can be negatively affected. As a consequence, a change of the electrical properties could be expected as they are linked to these material characteristics. In addition, during operation, the extruded cable will be subjected to electrical, thermal, mechanical and environmental stresses that can have an influence on the ageing rate of the entire cable construction. This is a critical issue since it will affect the safe operation of the extruded cable and could lead to a premature failure. However, based on the existing literature, it seems that the thermal ageing is not a problem for AC cables in operation and that failures in the field could not be related to high temperature and electrical loading. Due to the more recent implementation of extruded HVDC cables, such statistical information is not yet available, but 15 years of good operational experience is reported. A novel unfilled cross-linkable polyethylene (XLPE) material has recently been developed. Extruded HVDC cables using this material as insulation have been qualified for voltage level of 525kV, according to the Cigre recommendation TB 496. In order to reach these high voltage levels, the insulation material has improved physical and chemical cleanliness as well as an optimised composition based on a lower peroxide level leading to low DC electric conductivity and controlled space charge accumulation. In combination with the appropriate control of the key properties, long term performance of the insulation material, especially mechanical and ageing properties also need to be safeguarded. The purpose of this paper is an investigation of the long term mechanical and thermal performance of HVDC insulation material. Due to its macroscopic properties, conventional HVDC XLPE insulation has very good mechanical properties at elevated temperature and as a consequence the extruded cable maintains its shape and integrity even at overload temperature. To demonstrate the long term mechanical performance and that the dimensional stability during operation are maintained even though the insulation material has a lower cross-linking level, key mechanical properties such as creep and stress crack resistance at different temperatures have been measured in comparison to conventional HVDC XLPE. The thermo-oxidative ageing of insulation material has also been studied. Influence of ageing temperature on mechanical and key electrical properties will be discussed in relation to the chemical and physical characteristics of the material. The combined influence of electrical and thermal constraints on dielectric properties will be addressed in a separate paper. JICABLE15_0178.doc Long-term effect of water tree aged cables injected by silicone liquid under continuous electrical and thermal stress Kai Zhou, Kangle Li, Tianhua Li, Mingliang Yang (1) 1 - School of Electrical Engineering and Information,Sichuan University,Chengdu, Sichuan, 610065, P. R. China, zhoukai_cqu@163.com, likangle109@126.com, lier_tiantian@126.com, mlyang1029@163.com Water trees are regarded as the main reason for insulation degradation of XLPE cables in a moist environment. A silicone rejuvenation technology is used to rejuvenate the water tree aged XLPE cables for many years. However, these rejuvenated cables likely initiate water trees again under inservice condition. To investigate the long-term effect of water tree aged cables Injected by the silicone liquid, water-tree cable samples treated by the silicone fluid were subjected to aging experiment under electrical and thermal stress for a long time, and characteristics of water tree and electrical performance of the samples were compared during the process. A water tree accelerated aging system with a needle electrode was employed to obtain water tree aged cable samples. After four weeks aging experiment, water trees in slices can be clearly observed by a microscope. A half samples of these water tree aged samples were injected with silicone liquid, the other half samples were kept untreated. All samples were subjected to the electrical and thermal aging for six weeks again. During the process of reaging, dielectric loss factors of the samples were measured every week, and the sizes of water trees in samples were counted.Microscopic examination and dielectric loss factor tests show that water trees in treated samples are significantly shorter than untreated samples during the process of reaging. Electrical performance of the treated samples are also much better than untreated samples. Based on the results, it's further confirmed that the rejuvenation fluid have long-term effect on inhibiting water tree propagation and extending the lifetime of water tree aged cables. Key words Water tree; XLPE cables; rejuvenation; long-term effect; electrical performance JICABLE15_0179.doc Snaking of cables in empty pipes. Paolo MAIOLI (1), Marco BACCHINI (2) 1 - Prysmian S.p.A, Milan, Italy, paolo.maioli@prysmiangroup.com 2 - Prysmian Power Link S.r.l, Milan, Italy, marco.bacchini@prysmiangroup.com The paper describes the snaking of cables in pipes left empty, modeled with an analytical calculation method developed by the authors. The theory has been verified with experimental tests that demonstrates its validity. The paper provides a presentation of the theory, experimental tests and indications for cable designer. The theory is based on the following main observation and principles: 1 - Cables in empty pipes may change their configuration from rigid to a snaked configuration if the conductor temperature increase above certain defined critical value. 2 - The configuration of the cables in empty pipes is the one which implies the minimum energy for the cable itself (Energetic model). It is possible to formulate the total energy of the cable, as the sum of Axial, Bending and Gravitational Energy, for any configuration of the cable. It is possible to find the analytical equation of cable snaking with minimizing the value of the total energy. Analytical formulas are complex but can be easily imputed into a personal computer and solved. Comparison of total energy computed for straight, sinusoidal and helical configuration, allows determining the deformation preferred by the cable. The solution of the equations provides also the critical temperature which triggers the passage of the cable from the straight configuration to the snaked configuration. One of the most important results of the developed theory and experimental tests is that the pitch of the first snaking is kept during all the following load cycles. This basic result of the pitch conservation allows the calculation of the various parameters such as cable thrust and sheath strain and fatigue along the whole life of the cable. For low thermal rise the only existing configuration is the straight configuration, but above a critical temperature the sinusoidal configuration becomes possible and most probably the cable will tent to assume this configuration; for very high thermal rise and stiff cables, the helical configuration becomes possible. Experimental tests. The theory and the calculation model have been verified by means of full scale experimental tests, based on the installation of a cable inside a long rigid transparent pipe Fig. 1: Snaked cable into a pipe. JICABLE15_0179.doc Different HV cable types have been tested with different material of conductor and metallic sheath: the cables have been blocked to the ground at the two extremities. Load cycles at 90°C of conductor temperature have been executed, but temperature up to 200°C have been also tested, to verify the cable behavior at short circuit extreme conditions. The picture reports the snaking of a cable inside the empty pipe taken at high temperature during the thermo mechanical tests. The main conclusions that can be drawn as a result of the mathematical model and verification tests are: • • • • • The cable snakes initially as a cylindrical sinusoid, touching the pipe walls. The pitch is created and does not change during the following thermal cycles. The sinusoid climbs the pipe walls and allocates an extra-length of cable, thus reducing the thrust that can be computed analytically. The fatigue life of the cable sheath is computed on the cylindrical sinusoid configuration, in the position of highest deformation. Computation of thrust and fatigue life of the sheath can be done analytically. JICABLE E15_0180.do ocx Lifetime pred diction of o an ex xternal protectio p on of co oldshrinkable jo oint in EPDM E ru ubber su ubjected d to therrmal age eing Mouna BEN HASSINE (1), Mo oussa NAÏT T-ABDELAZIZ (2), Fahm mi ZAÏRI (2)), Xavier CO OLIN (3), Christop phe TOURCH HER (1), Gre egory MARQ UE (1) 1 - EDF R&D, avenu ue des Renarrdières, F-77 7818 Moret-s sur-Loing, Fra ance, moun na.ben-hassine@edf.fr, christophe.to c urcher@edf..fr, gregory.m marque@edff.fr. 2 - Laboratoire de Mécanique de Lille (LML), UMR CNRS S 8107, Unive ersité Lille 1 Sciences et Technologies, ave enue Paul La angevin, F-5 59650 Villene euve d’Ascq, France, mousssa.nait-abde elaziz@polyttech-lille.fr, fa ahmi.zairi@p polytech-lille..fr MR CNRS 8006, 3 - Laboratoire des Procédés P et Ingénierie I en n Mécanique e et Matériaux x (PIMM), UM 8 Arts et Mé étiers ParisTe ech, 151 bou ulevard de l’H Hôpital, F-75 5013 Paris, France, F xavieer.colin@ens sam.eu, The aim m of the pressent work is s to study th he conseque ences of the ermal oxidattion on the chemical structure e and mecha anical behavior of an indu ustrial Ethyle ene-Propylen ne-Diene Moonomer (EPD DM) used as an exxternal protecction of a colld shrinkablle joint. Based on these results, a chhemo-mecha anical tool has bee en develope ed for prediicting the sstretch ratio at failure. This tool iss composed d of two complem mentary levells: First of all, the “chemiical” level tha at calculates the alteratioon kinetics att both the molecula ar and macromolecular scales. s The average mo olar mass of the elasticaally active ch hains (i.e. between n crosslinks) Mc is used as the main indicator of the macrom molecular nettwork degrad dation. In es the ultima the other hand, the “mechanical” level deduce ate mechanic cal propertiess. Experimentally, the changes c in Mc have been n determined d by swelling tests in cycllohexane solvent and the chan nges in ultim mate mecha anical prope erties have been b determ mined by coombining the e fracture mechaniics theory with the intrins sic defect con ncept (Fig.1). EPD DM swelling in the cyclohexane solve nt. mechanics te ests. Specimen for fracture m Fig g. 1: (a) Swellling tests an nd (b) fracture e mechanics s measuremeents In our ap pproach, the e time-temperature equiva alence princ ciple is introduced, a shiftt factor obey ying to an Arrheniu us law is derrived, and master curvess are built as s well for the e average m molar mass as a for the ultimate mechanical properties. We have e pointed out the square e root depend dence of the e fracture ene ergy (in term m of critical in ntegral J) with Mc. Moreover, it is shown n that the m mechanical la aw behaviorr could be aapproximated by the phantom m network the eory, which allows a to rela ate the strain n energy density function to Mc. Assuming that the fractture of a smo ooth specime en (not notch hed) is the consequence c e of a virtual intrinsic defe ect which size can n be easily estimated, e th he stretch ra atio at break k can be therefore compputed for any y thermal ageing ccondition. Finally, tthe develope ed tool pred dicts satisfyin ngly ultimate e properties of thermallyy aged EPD DM based rubbers in air betwee en 130 and 170°C, 1 makin ng this appro oach a usefu ul tool for preedicting life time when designin ng different ru ubber compo onents for mo oderate to high temperature environm ments. JICABLE15_0181.doc Key technical research on submarine optic fiber and power composite cable with long length, three cores & high voltage Jianmin ZHANG(1), Shuhong XIE (1) 1 - Zhongtian Technology Submarine Cable Co., Ltd, Nantong, China, zhangjm@chinaztt.com, xiesh@chinaztt.com There are many differences between high voltage (with long length & three cores) and low/middle voltage of submarine optic fiber and power composite cable on the production technology and testing aspects. This article focuses on the key technical research of long length, high voltage submarine composite cable. E.g. extrusion technology, power cores and optic fiber cores assembly, optic fiber cable protection, main performance tests, etc. 1 Summary 1.1 Application scope of product: The product is mainly used high capacity supply network between the main land and island; near offshore oil exploration, platforms group supply network; offshore wind power generation transmitting to the mainland. 1.2 Advantage of three cores comparing to the single core cable: Save the submarine route resources, very low electromagnetic consume, low cost for the fabrication and maintenance. 1.3 Manufacturing background: The first offshore wind power of China south power grid—Zhuhai Guishan offshore wind power demonstration project started in March of 2013. Electric energy generated by offshore wind turbine, was transmitted to the mainland through two runs (20 km for each run), three cores, 110kV submarine composite cable. At the same time, the optic fiber cable was used to complete the communication, control equipment and monitor the running status of submarine composite cable. 2 Key technical research 2.1 Conductor water blocking technology research for high voltage submarine power cable: The conductor water blocking (semi-conductive water blocking compound is filled inside and wrapping the water blocking tape over the conductor) performance has been verified by the production experience, lots of test researches to make sure the shorter repair length after the submarine cable damaged. 2.2 Insulation production technology for the long length submarine cable: The insulation continuous length of high voltage cable has been extended, Quantity of factory joint has been reduced, the stability of the cable has been improved through improving the production die, adjust the insulation extrusion temperature and filter net arrangement. 2.3 Research on the assembly, armoring technology: The structure after assembly has been stabilized and the optic fiber cable has also been protected well through the research on rotating tank vertical assembly line, assembly pitch, filling type, etc. 3 Tests for long length and completed submarine cable In order to complete the AC high voltage test, the capacity of test equipment will be very big especially for the long length and high voltage submarine cable. This paragraph will mainly introduce the frequency conversion series resonance test equipment is used to do the routine test and factory acceptance test and also the configuration of the test equipment and calculation method will be introduced. 4 Conclusion Construction design, equipment chose, production technology and reasonability of test method of long length submarine composite cable have been verified by the fabrication and tests of 40 km (two runs) submarine cable.The proposal for the long length submarine fabrication has also been recommended. JICABLE E15_0182.do oc Bend ding stifffness off subma arine cables. Paolo MA AIOLI (1), 1 - Prysm mian S.p.A, viale v Sarca 222, 2 20126 M Milan, Italy, paolo.maioli@ p @prysmiangrroup.com The deve elopment of HV large sec ction three ccore power ca able, to conn nect wind farm ms to the shore, is a greatt challenge because b such h cables are very large. The T installatio on necessitaates a precise e know wledge of the mechanical parameters such as the bending stifffness, in ordeer to use app propriate equip pment and prrocedures. For F such reassons a speciffic test equip pment has beeen develope ed, in orderr to provide accurate a mea asurement off the flexural characteristtics of the caables. The app paratus is an innovative implementatiion of the thrree points be ending meth od, where th he cables are bentt in the horizzontal plane (Figure 1). T The cable is supported by b specificallly designed rollers, in arge deflecttion and pre order to o minimize the t friction and allow la ecise measuurement on a broad spectrum m of deforma ations. This innovative ssolution allow ws also stud dying cabless subjected to creep, where se elf-deformation affects th he measures . ding of cable sample Fig.1 Bend Fig.2 Typic cal pattern off bending cyc cles At the e extremities, the t sample is resting on n two specia al rolling supports: the ddeformation is easily modeled d as a beam m and the Be ending Stiffn ness (BS) ca an be computed once thhe applied force f and deflectio ons are meassured. Moving sspeed can range r from 0.01 0 mm/secc to 1000 mm m/sec with maximum m defflection of 1 m at the center, tto span a wide w range of frequenccy and bend ding radii. The T apparatuus is very stiff, s with complian nce measure ed in 8 mm every 250 kg of load and a friction coe efficient of lesss than 1%. The testting apparatu us described d in Figure1 can be adap pted to any cable diameeter and expe ected BS value: th he BS=1/(48 d) PL3 form mula precisel y fit the exp periment, due e the minimiization of fric ction and assemblling uncertain nties. To chara acterize a ca able, a series s of measure es is perform med at consta ant speed, w with varying maximum m deflectio on (Figure 2),, or at consta ant maximum m deflection, with varying g maximum sspeed. Each measure comprise es a numberr complete bending b cycle es, because e repetition is s fundamentaal to pre-con nditioning the samp ple and to ve erify repeatab bility of the m measure. Various types of cab bles have been tested: siingle core an nd three core e, with differeent types of armoring or without armoring. The experim mental resullts show thatt bending stiffness depeends on man ny factors such as bending amplitude, spee ed of the defflection (that is cycle frequency), ambbient tempera ature and preconditioning of the sample. In nfluence of th he length of the t sample has h been sollved and an algorithm is provided, in order to cut the sa ample at a co orrect length to obtain trustable results ts. JICABLE15_0182.doc More information on the mechanical performance can be derived from the typical bending pattern reported in Figure 2: maximum deflecting force to bend the cable, hysteretic friction to prevent the onset of vortex shedding or force recovery after long term deflection. Results also show that the bending stiffness of cables decreases greatly when the bending radius becomes small, as a consequence of the high plasticity of the cable at large deformation. Moreover, the BS increases slowly when deformation speed is increased in bending cycles. Cable construction has a significant influence on BS, especially on polymeric materials and friction between adjacent layers and the simple correlation to the cable diameter is not sufficient to predict the BS value. JICABLE E15_0183.do ocx Therm mo-mec chanicall analysis of MV V underg ground long lin nks Houssam m TANZEGH HTI (1), Yves s BRUMENT (1), Roger TAMBRUN T (2 2) 1 - EDF R&D, Ecuellles, France houssam.tan h nzeghti@edf.fr , yves.brum ment@edf.frr 2 - ERDF F, Paris, France, roger.ta ambrun@erd df.fr he main goa One of th al of ERDF, French F DSO,, is the impro ovement of th he robustnesss of MV network and the quallity of energ gy supply in the quotidia an. Due to climatic eve ents, particullarly storms,, the MV overhead d network sh howed a certtain fragility o or vulnerability. For that reason, direct laying of cables c is now w one of the most wide-spread install ation mode in i France in case o of MV overhe ead lines ren newal. ERDF F buried arou und 3 300 km m by year unntil 2010. To take face especially to climaticc hazards, ER RDF decided d to increase e the buried links value too 6 400 km by b year to reach 10 00 000 kilometers of MV buried links m more at horiz zon 2025. That’s w why ERDF and a EDF R& &D are stud dying the po ossibility to use u MV Undderground Long L Link (M.U.L.L L) for Distribu ution Network. The use of MV Unde erground Lon ng Link musst reduce sig gnificantly the number of accessories and im mprove the rreliability of th he medium voltage v netwoork From pre evious EDF R&D studies s we defined d the maxima al cable length by taking into account security constrain nts and cable e drum optim mization. Tho ose long links could reach up to 3 km and we e need to study th he consequ uences of th his long len ngth on following topics s: electric cuurrent in screen and thermo-m mechanical forces f at term minations and d in accesso ories. The pap per will exam mine the the eoretical me echanical fo orces that might be the result of hig gh loads in M.U.L L.L. Then the ere will be an n analysis off the case of a buried cab ble by takingg friction into account. To concclude we will w study the e resulting fforces at th he terminatio ons and thee optimal expansion e compenssator to minimize those forces by usin ng finite elem ments. Fig: Example of a MV Unde erground Joints with expansion compensator JICABLE15_0184.docx Development of XLPE Nano-Composite used for HVDC ±250kV Cable System compatible with LCC and VSC JH NAM (1), SI JEON (2), IH LEE (3), WK PARK (1), S HWANGBO (2), JH LEE (4), JT KIM (5), JY Koo (6) 1 - LS Cable & System, Gyeongi, Korea, jin-ho.nam@lscns.com wkpark@lscns.com 2 - LS Cable & System, Gyungbuk, Korea, sijeon@lscns.com hbs@honam.ac.kr 3 - LS Cable & System, Gangwon, Korea, ganaihl@lscns.com 4 - Daejin University, Gyeongi, Korea, jtkim@daejin.ac.kr 5 - Hoseo University, Chungnam, Korea, leejh@hoseo.edu 6 - Hanyang University, Gyeongi, Korea, koojy@hanyang.ac.kr Since 1960s, XLPE has been widely used for electric power cable insulation ascribed to its relatively preferred technical advantages, such as high breakdown strength, excellent thermal and mechanical properties. However, its use for DC power transmission cable has not been remarkably accepted considering the decrease in breakdown strength during the operation and the accumulation of space charge. Since the latter could enhance the local electric field distribution inside the cable insulation system, it has been suggested to introduce nanoparticles into XLPE for being pertinently suppressed. In Korea, XLPE Nano-composite has been developed after several years’ research works for HVDC ±250kV cable system compatible with LCC & VSC type. Since 2009, the related research work has been followed: the synthesis and surface treatment of nanoparticles and manufacturing process of Nano-composite XLPE has been successfully developed for the application to HVDC transmission cable. For this purpose, several numbers of tests have been carried out with the specially designed specimens fabricated with developed Nano-composite XLPE: DC volume resistivity, space charge accumulations, dielectric breakdown strengths, impulse breakdown and superimposed impulse. In addition, space charge accumulation in model cable has been also carefully investigated. The prototype DC XLPE shows very low level of space charge accumulation with homo-charge characteristics and noticeably low field enhancement below 120%. DC volume resistivity is measured over 1017 cm at room temperature and 1015 cm at 90oC under the 20kV/mm and particularly less dependency on temperature is confirmed; one of the most important characteristics for DC transmission. Besides, other technical requirements for the mass production such as long-period extrusion have been satisfied, by which long cable system with minimum number of joints could be realizable. A model cable has been fabricated by using the developed compound and then put into the fundamental tests: DC Breakdown and Impulse breakdown. Moreover, space charge measuring devices for model cable are developed; however, further investigation is being conducted to be implemented to the real size cable. Based on the above empirical results, ±250kV XLPE cable system for LCC has been designed and manufactured at Donghae plant of LS Cable & System. And then, relevant tests have been carried out according to CIGRE TB 496 LCC protocol: load cycle, polarity reversal, superimposed switching and lightning impulse over the DC, and finally subsequent DC. These tests for the qualification have been carried out at KEPCO Gochang Test yard, entitled as KOLAS (Korea Laboratory Accreditation Scheme). In addition, after fulfilling the required tests for LCC cable, the tested cable has been again put into test according to the recommended additional process of CIGRE TB 496, such as superimposed lightning impulse test, which is required for VSC. More research works are currently being carried out for the improvement of electrical properties for the purpose of the higher voltage grade beyond ±250kV. Key words Nano-composite; XLPE; HVDC; Cable System; Cigre TB 496; LCC & VSC; KOLAS JICABLE15_0185.docx Solutions for thefts in overhead-underground Transition Towers. Álvaro MARCELO (1), Rafael GARCÍA (1), Maria Dolores LÓPEZ-MENCHERO (1) 1 - Red Eléctrica de España, Madrid, España, amarcelo@ree.es, rafgarcia@ree.es, malopez@ree.es Red Eléctrica de España (REE) is a Transmission System Operator and the main owner of transmission assets in Spain. The scope of their responsibilities includes management, development and maintenance operations. Red Eléctrica de España, currently, owns 40,044 km of 400kV, 220kV and 66kV overhead and underground transmission lines The first theft of a screens cable’s and arrester’s downspouts by a transition overhead-underground tower (hereafter TT) in the Community of Madrid occurred the 3th of June 2009. During 2010 and 2011 sporadic thefts occurred and it is from 2011 when this type of vandalism acts was multiplied. Although initially these thefts occurred in Madrid, then spread to other areas of Spain (Levante, Valladolid and Canary Islands). At first, Red Eléctrica de España (hereafter REE) simply replaced the stolen items and repaired the damage caused. However, when any of the previously stolen thefts in TT began to be repeated, REE identified the need to shield the TT. Over time, the robberies, which initially affected only the nearest ground segment, were evolving, so they began to occur even with some type of shield and in higher areas of the tower, just from a few centimeters of the terminations. REE has been improving their shields. The first consisted of placing a tube, secured by conventional clamps, where the cable which was centralizing the earth connection of the arresters and terminations got inside. Subsequently, this system got to to a more complete model in which the support is fully shielded from the inside of the base to the terminations and surge arresters support. To date, there has been no robbery in towers with this kind of "super-shield", so we can say that this system is working well. Fig. 1 shows how the number of thefts has gone down while the number of armour-plates has increased. Fig. 1. Changes in the number of robberies and shields. JICABLE15_0186.doc Eco-friendly nanodielectrics with enhanced thermal and electrical properties for HVDC cable insulation Yao ZHOU (1), Jinliang HE (1), Jun HU (1), Bin DANG (1) 1 - State Key Lab of Power Systems, Department of Electrical Engineering, Tsinghua University, Beijing, China, zhouyao14@mails.tsinghua.edu.cn, hejl@tsinghua.edu.cn, hjun@tsinghua.edu.cn, db13@mails.tsinghua.edu.cn With the development of power systems, some problems have occurred in HVAC transmission system, it is required to develop a new transmission mode with large transmission capacity and long transmission distance. However HVDC transmission system with low construction investment, low transmission loss, large transmission capacity is easy to control and has less impact on the environment. Therefore HVDC power transmission especially HVDC cable transmission will be popular in the future. For most modern extruded HVDC cables, crosslinking polyethylene (XLPE) is used as their insulation material, but XLPE is very difficult to be recycled after using due to its thermoset nature. Meanwhile, the tolerable temperature of XLPE is not very high which limits the increase of transmission capacity and operating temperature. So it is urgent to develop a new type of eco-friendly HVDC cable insulation material to meet the requirements of environmental protection and sustainable development. As a cable insulation material, the thermal, mechanical, thermo-mechanical and electrical properties of the material must be taken into account. In particular, the space charge accumulation characteristics which has large effect on the degradation and breakdown of insulation should be considered. Polypropylene (PP) which is a thermoplastic material with excellent thermal and electrical properties is very easy to be recycled and is a good base material for cable insulation, but the mechanical properties of PP are very poor and easy to fracture. In our previous study, polyolefin elastomer (POE) was used to improve the mechanical properties of PP by melt mixing. The properties of PP/POE blends were examined to evaluate the potential of the blends for HVDC cable insulation application. It has shown that PP/POE blends have good thermal, mechanical and electrical properties compared with XLPE and it is a good candidate for HVDC cable insulation. But the hetero space charge accumulation is still a problem which is very unfavorable for HVDC cable insulation. Recent researches in nanodielectrics have shown that the introduction of small amount of nanoparticles in polymer matrix has great effect on improving the electrical properties of the nancomposite, such as increasing breakdown strength, dielectric polarization, volume resistivity and suppressing space charge accumulation. The excellent behaviors of nanodielectrics should be attributed to the large nanoparticle-polymer interfacial areas. Although the mechanism of suppressing space charge by nanoparticles is still not very clear, nanodielectrics have attracted great attention in both industry and academic. Based on our previous study of PP/POE blends, in this investigation we use nano-MgO particles to suppress the space charge accumulation and further improve the properties of the blends to make it more applicable. The nano-MgO particles were surface modified by silane coupling agent to improve the compatibility of the nanoparticles and the polymer matrix. We have studied the thermal, mechanical and electrical properties of the MgO/PP/POE nanodielectrics. It is shown that the introduction of nano-MgO particles could enhance the electrical properties of the blends due to suppressing space charge accumulation and the thermal properties of the nanocomposite are still good enough. JICABLE E15_0187.do oc AC re esistanc ce of submarine e cables s. Paolo MA AIOLI (1), Massimo M BEC CHIS (1); Ga aia DELL’ANNA (2) 1 - Prysm mian S.p.A, Milan, M Italy, paolo.ma aioli@prysmiangroup.com m, massimo..bechis@pry ysmiangroup.com 2 - Prysm mian Power Link S.r.l, Milan, Italy, ga aia.dellanna@ @prysmiangrroup.com The devvelopment off HV large section three e core powerr cables is a great challeenge because of the correct d determination of losses dissipated in nto the armouring. The paper illustrrates measu urements, calculatio ons and mod delling of los sses in orde r to design a state-of-the e-art cable, w with optimise ed use of materialss. The dessign of such large cable es, to be ussed for exam mple in off-shore wind faarms, neces ssitates a precise kknowledge of o the losses, in order to p provide accurate values of o the electriccal characterristics. Fig.1 Infrared image Fig.2 F Visible iimage a generate ed into the arrmouring (arm moured cablee shown in Figure F 2); Figure 1 shows how the losses are are detected with a therm mo camera. IIt can be cle early seen that the lossess are concen ntrated in losses a the part of the armou uring closer to t the powerr cables and follow the direction of thee power core e and not that of th he armouring g wires. The paper clearrly describes that heat is definitely geenerated into o the wire and it is not coming from f the conductors. The expe erimental evvidence is tha at the losses are affected d by the way how the cabble is designe ed. It is also o known thatt conductor resistance in ncreases witth current, so o that it is im mportant to make m the measure ement at the rated curren nt and freque ency: a test bench b has be een developeed in order to provide accurate e measurement of the electrical e cha aracteristics of these larg ge cables. T The cleanness of the power frrequency sin ne wave has been verifie ed and any distortion d dettected and eeliminated. The T paper describe es the effectss of presence e of superpossed harmonics on cable resistance a nd impedanc ce. The leng gth of the ca able sample is i important for the accuracy of the measures, m frrom one poin nt of view to limit sside effects and from th he other to e economically y inject the rated currennt; cable arrranged in straight configuratio on and witho out close e extraneous metallic m partts is of greeat help in reducing uncertain nties and facilitate the operations o o of removing the t armourin ng. The pow wer requeste ed for the injection of the current into the sa ample is prop portional to the cable length and increeases rapidly y with the frequenccy when harm monics of the e current are e added. It is posssible to disasssemble the armouring prrogressively, until the wh hole armor is removed. In n this way the effecct of the num mber of wire es and the e electric conta act between them can bee studied. The paper shows th hat wire-to-w wire insulatio on has neglig gible effect on total loss ses and thatt the losses increase JICABLE15_0187.doc almost linearly with number of wires. It has been verified that left handed and right handed currents systems give the same losses. Connections on conductors and sheaths, at sample extremities, have to be realised with care and expertise, because they can introduce additional resistance and thus reducing the current circulating in the sheaths and the corresponding measured losses. JICABLE15_0188.docx XLPE cables with aluminium laminated sheath Terje ROENNINGEN, Boerre Johansen SIVERTSVOLL (1), Hallvard FAREMO, Are BRUASET, Atle PEDERSEN, Jens Kristian LERVIK (2) 1 - Siemens AS 2 - SINTEF Energy Research XLPE power cables with aluminium laminated sheath was developed to improve the long term wet ageing performance of power cables and has been in use for nearly 25 years. These cables are even common in indoor installations (no humid environment). Operational experiences on single core cables have not been as good as expected since several faults (insulation breakdown) have occurred. The problems have been related to overheating due to large heat development by capacitive and induced currents in the aluminium laminate/copper screen. The main reason of the fault is due to poor performance of the contact between the laminate and copper screen. The faults occur close to cable joints and at the end terminations, but may also occur close to cable straps where the cable is compressed and the copper screen may be in contact with the laminate. Essential information why and how to carry out the screen terminations may not always be sufficiently emphasized. Preliminary theoretical studies and laboratory tests have been carried out in order to give basis for determining the currents and generated heat in the aluminium laminate and copper screen. This is carried out on alternative configurations (trefoil, flat formation) and cross sections of cable conductor and aluminium laminate/ copper screen and cover normal operation and fault conditions (short circuit, ground fault). In existing cable installations decision analyses are required weather replacement of the cable installation is required or repair is recommended. Regarding planned installations it should be evaluated if the watertight design with aluminium laminated sheath is needed. Alternative solutions by use of three core cables may in some cases be more reliable if watertight cables are required. In case of repair it should be evaluated if surge arresters for protection against atmospheric and switching over voltages should be used, especially if single point grounding screens are used. JICABLE15_0189.docx Effectiveness and comparability of condition tests on MV cables Peter BUYS (1), Dirk VAN HOUWELINGEN (1), 1 - Stedin BV, Rotterdam, the Netherlands, peter.buys@stedin.net, dik.vanhouwelingen@stedin.net As most European utilities, Stedin operates a large population of ageing MV cables as part of its network. Many cables have reached an age of 40 years or more, and are nearing the end of their expected technical life span. As old cables tend to be less reliable, the issue of remaining life expectancy and condition of cables is an important factor in asset management. To determine the condition of aged cable populations testing on (a statistical significant sample of) aged populations is necessary. The tests indicate changes in cable materials and other early warning signals of cable failures. Even if we limit ourselves in this paper to the use of electrical tests, a large number of techniques are available for pro-active testing of cables. These include: - PD measurements, both on-line and off-line - Tan delta measurements - Voltage tests: VLF, 50 Hz, 20-300 Hz oscillating voltage, Damped AC - Impedance tests - Etc. Each technique is tailored to a specific effect and can be linked to certain failure modes of the cable system. Based on failure statistics from the past, the relative frequency of different failures modes can be determined. From this, the optimal mix of measurements, which effectively addresses the most common faults in our grid, can be chosen. Of course, this has to be re-evaluated periodically, as bad populations are replaced and remaining populations get older. A second consideration on the number and type of tests, deals with the fact that all measurements imply the possibility of an induced failure. This can result from stressing the system (voltage tests), the need to switch in the system to perform a test (all off line tests) or due to expanding the system with measurement devices (on-line systems). We present the results of a survey, which indicated that the advantages for voltage tests outweigh the induced failures. On a number of occasions, results of first measurement on an old cable proved indecisive. Then a second measurement with another technique was carried out. We present some examples of that, both with supportive and contradictory results. Further analyses are presented, which will explain these cases. Key words Condition assessment; Asset management; Test methods; JICABLE15_0190.doc Acceptance criteria in nuclear power plant cable qualification Vít PLAČEK (1), Jan KÁBRT (2), Vladimír HNÁT (3), Pavel ŽÁK (4) 1 - ÚJV Řež, a. s., Hlavní 130, Řež, 250 68 Husinec, Czech Republic, vit.placek@ujv.cz , jan.kabrt@ujv.cz (2), vladimir.hnat@ujv.cz (3), pavel.zak@ujv.cz (4) Nuclear power plant (NPP) equipment qualification is a fundamental process to test whether safety systems and equipment can perform their intended functions during normal operation, as well as during postulated accidents (DBE). In the process of qualification all samples are subjected to diagnostic measurements to test whether the equipment fulfills all previously defined acceptance criteria. The criteria are usually limit values of certain properties beyond which the degree of deterioration is considered to reduce the material´s ability to withstand stress encountered in the course of the regular service and/or DBE. The extent of measured properties and the acceptance criteria may vary and, generally, they depend on a specific cable application in each respective NPP. The most commonly tested parameters are insulation resistance, voltage withstand and mechanical properties of polymeric insulations. The acceptance (failure) criteria shall be, on the one hand, conservative enough to sufficiently cover margins and uncertainties and, on the other hand, they shall not be too demanding to give needlessly negative results. In this paper some acceptance criteria are explained and proposed. The qualification tests include a number of measurements at the beginning, in the course of and at the end of the testing procedure, and results of such tests determine whether the cable passes the type test or not. However, standards and regulations do not always contain a sufficiently accurate specification of the parameters to be measured or the limit values which shall not be exceeded. Based on many years of experience with the qualification of NPP equipment we have proposed to use the following functional properties and limit values: - The properties of the cable shall meet the design requirements throughout the entire time of operation, as long as such requirements are accurately specified. If the design requirements are not detailed enough we have proposed that at least the following properties should be demonstrated: - Properties of a new cable shall always meet the manufacturer´s technical specifications. - For pre-aged cables, before DBE simulation, the elongation at break of the sheath and core insulation shall be greater than 50% absolute. - Volume resistivity shall be always, i.e. also in the course of DBE simulation, greater than 1010 Ωcm. - The polarization index shall not drop below 1. - In the course of DBE simulation the cable shall be supplied by the operating voltage and shall remain functional. - Further, the cable shall meet the voltage withstand test, for which the test conditions - voltage, test time, medium - are relatively well defined by the current national standards. - No fluid from the surrounding environment (water, steam) shall be detected inside the cable For some cables, e.g. coaxial or communication cables, it is advisable to measure also other properties decisive for keeping of the function, such as capacity, signal attenuation etc. Throughout the test the values shall not differ from those in the manufacturer´s technical specifications and/or values predictable based on known physical laws (e.g. growth of attenuation as a result of growing resistivity of metals with the increasing temperature, etc.). Key words: qualification, cable, acceptance criteria, nuclear power plants JICABLE15_0191.doc A novel cooling solution for an intersection of a 2x2 duct bank with HV cables crossed by a steam pipe George ANDERS (1), Heinrich BRAKELMANN (2), Sudhakar CHERUKUPALLI (3) 1.- Lodz University of Technology, Lodz, Poland, george.anders@bell.net 2.- BCC Cable Consulting and University of Duisburg, Germany, heinrich.brakelmann@ets.uni-duisburg-essen.de 3.- BC Hydro, Vancouver, Canada, sudhakar.cherukupalli@bchydro.com This paper presents the results of ampacity studies and proposed remedial actions for the situation where a steam pipe crosses a duct bank with HV transmission cables. A 2X2-transmission duct-bank intersects a steam crossing in downtown Vancouver. This intersecting steam line, which was super-insulated, is likely to pose some concern for long-term thermal performance of the transmission cable and appears to be thermally limiting for the cable corridor. There is an urgent need to develop a solution to mitigate this “hot spot” and to allow the transmission cable to be able to carry its rated current (1250A). The soil temperature measured below the steam pipe at the depth of proposed transmission duct bank prior to its installation ranged from 35°C to 45°C. In the first set of studies, two computer programs (CYMCAP and KATRAS) were used to model the situation when the steam pipe is parallel to the duct bank and then further calculations were performed with the 90° crossing. The calculations were performed with the thermal parameters of the steam pipe insulation supplied by B.C. Hydro and confirmed with the internet data about the thermal properties of the insulation materials of the steam pipe. In the additional studies, the measurements performed by B.C. Hydro were used to determine the most likely equivalent thermal resistivity of the steam pipe insulation and to determine under what conditions the cable conductor temperature might exceed the allowable limit. Taking the nominal values for the steam pipe insulation parameters, the equivalent thermal resistivity of this insulation is estimated to be equal to 19.2°K.m/W. Taking into account a possible aging, however, as well as the measured temperature values, the estimated value of this parameter is more likely to be 9.6°K.m/W. The second set of studies involved application of a new solution involving use of the gravitational water cooling system. The system is described in detail in the paper. Mathematical models for several possible solutions involving both water and air gravitational cooling, taking the crossing geometry into account, were developed. Practical concerns of BC Hydro engineers involving safety and public utility regulations as well as practicability of the proposed solution are also discussed in the paper. The diagram shows the proposed solution with the gravitational water cooling pipes. In this case, the steam pipe crosses the duct bank at 90°C; however, both the parallel and angled crossing situations can be investigated by the proposed model. The major findings of the studies can be summarized as follows: In the most adverse condition of the soil and the steam pipe coating the conductor temperature will exceed 90°C notwithstanding the effort to increase duct spacing at the intersection to improve the cable’s thermal performance. Remedial action involving water pipes seems to be both inexpensive and effective solution for cooling down the intersection of the steam pipe with the duct bank thus ameliorating the anticipated thermal limit for the cable ratings. JICABLE E15_0192.do ocx Dear administtration, We successfu ully submitted two ab bstracts , No.0192 annd 0194, for Jicable 2015. 2 We would like to t clarify that abstracct 0192 is the result of o two year study with imp portant collaborationss with other raw mate erial suppliers (Arkem ma, Addivant) and ma achine producers (Bu uss) and we would reeally like to present it as an oral contribution. A At the same time, durring the project, we also a found an interestting topic, summarize ed in abstract 0194, that is worth to be knnown to the public bu ut is probably more fitted forr a poster presentatio on. Therefore, our wis sh is that the abstracct No.0192 can be co onsidered to give a paper p with oral preseentation, and the absttract No. 0194 for a poster to opic. Daniele Bonacc chi, Ph.D. Development scientist, R&D polym mer applications High quality carbon black to o surpas ss traditional so olution for f HV semic cons? Daniele BONACCHI (1), Christin ne VAN BELL LINGEN (2),, Denis LABB BÉ (3) 1 - IMER RYS Graphite e & Carbon, Bodio, Switzzerland, danie ele.bonacchi@ @imerys.com m, christine.vvanbellingen n@imerys.com 2 - P&M Cable Conssulting LLC, Geneva, G Swiitzerland, dla abbe@pm-ch h.com The efficciency of the e semiconduc ctive layer de epends on itts electrical conductivity c tthat is guara anteed by the presence of cond ductive carbo on black in t he semicon formulation. It has been proven that electrical aging me echanisms are a directly lin nked to semiicon protrusion as they lo ocally increasse the electrical field. Fig. 1: Conductiive carbon bllack TEM pic cture As carbo on black is an essentia al constituentt of semicon n compound d, its quality affects the semicon performa ance and hence the final cable lifetim me. Any impu urities presen nt in the raw w material such as grit (e.g. larg ge amorphou us carbon pa articles rema aining from production) p or o carbon blaack agglome erates not to mentio on ionic conttent are detriimental for th he final application. While the level of grits is an intrin nsic characte eristic of the carbon black used and w will remain in n the final compoun nd, the carb bon black agglomerates must be dis spersed and distributed bby proper prrocessing although h only speciffically design ned carbon b blacks can achieve a high level of disppersion. For example low surfa ace area is linked to larrge primary particles and d is known to t favor disppersion thanks to the better wetting of the e aggregates by the moltten polymer.. Also the high carbon bblack structurre (e.g. a high deg gree of brancching of the carbon c blackk aggregates s) is known to o ease dispeersion and distribution thanks to o the lower inter-aggrega ate interactio ons and that is why low surface area high structurre carbon black are e the only ch hoice for HV V and EHV ssemicon com mpounds. Alth hough surfacce smoothne ess is the primary requisite for a good sem miconductive compound, other charac cteristics aree essential fo or a good quality H HV cable. A proper p level of o volume ressistivity at the operating cable c tempe rature and its stability od cable manufacturing. Proper levvel of condu after the ermal cycling g is also crucial for goo uctivity is achieved d only at sp pecific carbo on black loa ading that is s in turn de ependent maainly on the e level of branchin ng or “structu ure” of the ca arbon black a aggregates and a the intrins sic carbon bllack conducttivity. In this article we will w show th hat an easyy-dispersible e, clean carbon black, with higherr intrinsic conductivity can be used u at lowe er loadings th han the commonly used carbon blackk in HV semicons. By direct co omparison we e will show the benefits o of using lowe er amount off the new carrbon black, especially e the lowe er viscosity and the lon nger scorch time of the compound while keepiing excellent surface smoothn ness and sta able conduc ctivity. Carbo on black ion nic impurities and moistture uptake that are transmittted to the final compound d and can iniitiate electric cal treeing will also be disscussed in de etail. JICABLE E15_0193.do ocx Developmen nt of a three-terrminal ready r HVDC in terconn nector betwe een France and d Great Britain via the island A Alderney y: the FAB p project Sean KE ELLY (1), Gro o WAERAAS S de SAINT M MARTIN (2) 1 - Transsmission Investment, UK K, sean.kelly@ @transmissio oninvestmen nt.com 2 - RTE, France, gro o.de-saint-ma artin@rte-fra nce.com The nee ed for stren ngthening off cross borrder capacities between n European countries is widely recognissed. In Octob ber 2014, an interconnecction target of 15% for 2030 was adoppted by the European E Council as a part of EU’s 2030 Climate C and Energy Polic cy Frameworrk. More speecifically, acc cording to the TYNDP1 2014, at a least 7 GW W additional interconnection capacity y between F rance and th he British Isles is n needed beforre 2030. The Fran nce-Alderneyy-Britain (FA AB) project, a 1400 MW DC interconn nector projecct, was selec cted as a Project o of Common Interest (PC CI) by the E EC in Octob ber 2013. It will contribuute to increa asing the interconn nection capa acity between France an nd Great Brittain. Moreove er, the link w will cross the e channel island off Alderney (which ( is currently electtrically isolated), hence creating an opportunity for for a future prroject that wo ould connectt to the onsh hore DC cablle running ac cross the islaand. This wo ould allow renewab ble generatio on in Alderne ey waters - the location of one of Europe’s E besst resources for tidalstream p power - to be e evacuated to t Britain and d France. The cab ble, which will link co onverter stattions in Me enuel (France) and Exxterer (UK),, will be approxim mately 220 km m, of which around a 170 kkm offshore and 50 km onshore. o RTE, the e French TSO O, develops the project ttogether with h FAB Link Ltd, L a joint veenture compa any, 50% owned b by Transmisssion Investm ment LLP and d 50% owne ed by Alderney Renewabble Energy. Technical T specifica ation of the cable c and the e converter sstations, follo owed by the launch of aan invitation to t tender, will be acchieved in 20 016, with a Final F Investm ment Decision n foreseen by y the end of 2017. During th he Front End d Engineerin ng Design sta age of the project, both companies hhave been working w to overcom me the challen nges associa ated with the e developmen nt of an interrconnector w with the follow wing main original ffeatures: - ccable laying in high energetic and low w sedimentary areas betw ween Francee and Alderney; - a an embedde ed three term minal functio on with two functions in n one single infrastructure, cross b border trade and evacua ation of renew wable energy y. JICABLE15_0193.docx The paper hence deals with the main design issues associated with these features: 1) Designing cable and cable protection in order to cope with the challenges linked to developing a submarine cable in a high energetic area with strong tidal currents and severe wave climate. 2) Determining optimal capacity for the “three-terminal ready” structure, ensuring: - a high level of interconnection capacity, while at the same time granting a smooth accommodation both on French and British on shore networks; - the right level level of modularity, in order to facilitate the development of tidal generation in Alderney, while maximising economies of scale through a high capacity link; - adequate design of control system in order to manage bidirectional flows with intermittent generation. [1] - The Ten Years Network Development Plan published by ENTSO-E JICABLE15_0194.docx The author propose the 192 oral and this one possibly poster Effect of carbon black selection on semiconductive compound water content and uptake behavior Daniele BONACCHI (1), Christine VAN BELLINGEN (2), Denis LABBÉ (3) 1 - IMERYS Graphite & Carbon, Bodio, Switzerland, daniele.bonacchi@imerys.com, christine.vanbellingen@imerys.com 2 - P&M, Geneva, Switzerland, dlabbe@pm-ch.com Water molecules entrapped in HV and EHV cable insulation are known to promote electrical treeing. As HV and EHV cables are usually protected from external water penetration, the main source of water molecules inside a cable is certainly the insulation compound used during cable manufacturing but also the water contained in both conductor and insulation shields that can migrate into the insulation layer during cable operation and contribute to electrical degradation. It should be remarked that water can have also a solvation effect on the ionic species present in the carbon black, for example, transition metal ions or organic ionic species, which can migrate as well in the insulation layer are known to catalyze polymer degradation. 1,4 adsorbed water (%) 1,2 RH=60% (desorption) max uptake (RH=95%) 1,0 0,8 0,6 0,4 0,2 0,0 MMM carbon black Acetylene carbon black Furnace carbon black Fig. 1: Water uptake of conductive carbon blacks in two different conditions by dynamic vapor sorption measurement. Conductive carbon black is one of the main constituents of semicon formulations and has its own moisture content, normally specified in the carbon black technical data sheet. The water content level depends on many factors, first of all it is related to the production process and to how it is packed, then it is related to the specific type of carbon black produced, for example extra conductive carbon blacks are known to have a very high moisture uptake. In extra conductive carbon black moisture uptake is normally related to the very high specific surface area of this material but also carbon blacks with similar surface area can differ in water content. Surface chemistry certainly plays a role in the water uptake mechanism, for example the presence of oxygen groups promotes water uptake but also the porosity (microporosity and mesoporosity) of the material can influence moisture adsorption. In this article we will compare the moisture uptake behavior and the ionic content of three different carbon blacks with similar surface area but produced with different production processes: furnace, acetylene and MMM processes. The moisture uptake behavior in different conditions will be analyzed (as packed, in ambient condition, after drying procedure, etc.) and correlated to specific characteristics of the carbon black (for example surface chemistry and porosity). Finally, the moisture content of the compounds made with the three different conductive carbon blacks will be analyzed and discussed in relation to cable manufacturing. JICABLE15_0195.docx Prediction of Power Cable Failure Rate Based on Failure History and Operational Conditions Swati SACHAN (1), Chengke ZHOU (1) Geraint BEVAN (1), Babakalli ALKALI (1) 1 - Glasgow Caledonian University, Cowcaddens Road, Glasgow, United Kingdom, G4 0BA Swati.sachan@gcu.ac.uk, C.zhou@gcu.ac.uk, Geraint.bevan@gcu.ac.uk, Babakalli.Alkali@gcu.ac.uk At present a good proportion of power cables are approaching the end of their operational life. Utility companies worldwide are under pressure from regulators and customers to control both cost and reliability. To overcome this challenge utility companies need an improved methodology to identify circuits in critical condition whilst making forecasts of future failures in order to optimize replacement. This paper proposes a methodology to predict the expected failures in the near future based on the stress endured by the cable on a daily basis, due to operational conditions, and at the same time captures the failure trend based on historical failure data. The existing UK regulatory approach of failure prediction is based on an age-based survival model which simulates the failure data. However, this approach ignores the fact that the life of the cable largely depends on the stress which it encounters during service life. The methodology used to develop the model is: 1. The total failure rate at any point of time is the combined rate of random and aging failures. The random failure occurrences are due to poor wor kmanship or manufacturing defects which cause intrinsic weakness; aging-related failures result from the accumulation of electro-thermal stress in daily load cycles due to seasonal load demand and ambient temperature. The electrical stress is associated with the electric field due to voltage and thermal stress, from generation of heat within the cable and impedance of heat dissipation to the surroundings due to high ambient temperature. 2. The historical failure data which captures the random failures are modeled using a nonhomogeneous Poisson process (nhpp) model. This is due to the consideration that the power cable is repairable. Usually when a cable fails, it is repaired by cutting out the piece which has faulted and splicing in a new piece. It is assumed that the condition of the cable after the repair is never “as good as new”. This is in contrast to the case of cable joint failures which are nonrepairable. 3. The operational conditions are modelled using a stochastic electro-thermal aging model in which stress accumulates according to cumulative Miner’s rule and which is considered stochastic in nature, following a Gaussian process. The failure rates from both models are combined using Bayesian approach. A comparative case study is demonstrated in jacketed and unjacketed XLPE cables which have experienced a total of 3541 failures for the years between 1980 and 2009 and for which distribution of the total number of cable failures in each month of year is available. Therefore, it can predict the expected number of failures in each year as well as each month or season of the year by utilizing monthly failure distribution. Results demonstrate that the failure rate model captures the aspects which affect the failure, such as, random failure causes and the combined effect of electrical-thermal stress. This model is applicable to the type of data available with utilities. JICABLE E15_0196.do ocx Results of 10 years after in nstallation tests s comb ined witth PD detec ction on n MV cab blesyste ems Frank DE E VRIES (1), Jacco SMIT T (1), John V VAN SLOGT TEREN (2) 1 - Electtrical Consulttant, Alkmaar, The Nethe erlands, frank.de.vries@alliander.com, jacco.smit@ @alliander.co om 2 - Senio or Assetmanager, Arnhem m, The Neth erlands, john n.van.slogterren@alliandeer.com In the N Netherlands new installed MV extrruded powercables are tested accoording NEN-HD 620 (Section J). The testts consist of a sheath tesst (5kV DC 5 minutes) an nd a voltagee withstand te est of the cable inssulation (3xU Uo VLF 15 minutes). m The e main functtions of these (destructivve) tests are to check the quality of the insstallation work of the cab ble. PD mea asurements are a mentioneed as an op ption. The requirem ments for PD are not desc cribed in the standard. In 2004 Alliander deccided to add PD measurrements in th heir after insttallation test policy. The benefit of the PD m measuremen nts as part of the after insstallation testt are: - T To have insig ght in the sta art condition parameters of the cables system (fingeerprint) T To have inssight in the condition o of the cable esystem, afte er the volta ge withstand test is p performed - In situations where high testvoltagess are not pos ssible PD tes sts at lower ttestvoltages can be a g good alterna ative (e.g. in nternal brea akdown when cable is connected c too an old sw witchgear, e external flashover in case of small sizze cableboxe es). - For some ab bnomalties in the accesssories, a vo oltage withsta and test migght not be enough to fforce a breakkdown Since 20 004 hundred ds of PD me easurements were perforrmed on new w installed ccable system ms. In the begin pe eriod the volttage withstand test was considered as the prima airy requirem ment. PD results were for inform mation only. In 2010, kno owledge rule es for PD we ere developed d and the PD D behavior became b a primary requirement for the after installation ttest at Alliand der. Over the e last years, dozens of ac ccessories and a few cable parts were taken out based on PD P activity during affter installatio on test. In many cases sevver abnormaliities were fou und which thre reatens the re eliability of the cable esystem, but also cases were w found wh here the reas son for PD wa as not obviouus. It is also discovered that cable esystems can n contain PD activity in acccessories bu ut still survive the after instaallation test. The pap per describe es the expe eriences witth PD mea asurements on new insstalled MV extruded powerca ables and th he developed requireme ents for PD behavior. Also A examplles are give en of PD behaviorr in relation to poor workm manship and d the design of accessorie es. Figure 7: Foun nd defect in 20kV 2 joint Figure 8: Related PD D behaviour JICABLE15_0197.docx Qualification of a 150kV Transition joint for connecting external gas pressure three-core cable with extruded singlecore cables Jos VAN ROSSUM (1), Robert BARTHOLOMEUS (1), Maurice OLTMANS (1), Henk GEENE (1), Riccardo BODEGA (1), Rob ROSS (2), Shima MOUSAVI GARGARI (2), Wouter VAN DOELAND (3) 1 - Prysmian Group, Delft, the Netherlands, jos.vanrossum@prysmiangroup.com, robert.bartholomeus@prysmiangroup.com, maurice.oltmans@prysmiangroup.com, henk.geene@prysmiangroup.com, riccardo.bodega@prysmiangroup.com 2 - TenneT, Arnhem, the Netherlands, rob.ross@tennet.eu, shima.mousavigargari@tennet.eu 3 - Energy Solutions (ENSOL), Delft, the Netherlands, w.van.doeland@ensol.nl The use of extruded cable systems for transmission and distribution circuits is ever increasing at the expense of LPOF and MI cables. Furthermore the number of manufacturers of these LPOF and MI cables is also decreasing and therefore the availability of such cables for repair works or re-routing is very limited in the future. Consequently it is becoming more and more common for a length of extruded cable to be introduced into a paper insulated cable circuit, requiring transition joints for the connection of the two cable types. For the project: ‘Zomerbed Verlaging Kampen’ for the Dutch TSO TenneT, Prysmian was requested to deliver and joint new 150kV extruded cables to the existing external gas pressure (EGP) cable with aid of new type of transition joint for the replacement of part of the 110kV EGP connection: ”ZwolleKampen Wit”, between joint M9 and Tower 60. For the design, development and prequalification of this new transition joint at 150kV level, Cigre TB 415 ‘test procedures for HV transition joints’ was followed. The paper highlights: - The basic design of the transition joint. By using state of the art technology, the transition joint was based on pre-fabricated components as much as possible, allowing pre-testing of these components. Furthermore the use of auxiliary equipment for this joint was eliminated, resulting in a smaller joint bay, lower weight, smaller footprint and reduction of total required equipment on site. - The electrical test loop set up. The testing of a three core EGP cable and single core extruded cables require special attention for the heating of the conductor: In this case a back-to-back test loop was chosen - The test of outer protection for the transition joint. Because of the dimensions of the joint, a special water tank was constructed to test the outer protection of this transition joint - The installation and commissioning test on site. The joint was successfully tested, installed and commissioned and is now in service since august 2014. JICABLE15_0198.doc Wet Designs for HV Submarine Power Cables Johan KARLSTRAND (1), Knut-Magne FURUHEIM (2), Sverre HVIDSTEN (3), Hallvard FAREMO (3) 1: JK Cablegrid Consulting AB, Karlskrona, SWEDEN, karlstrand@cablegrid.com 2: NEXANS Norway, Halden, NORWAY, knut-magne.furuheim@nexans.com 3: SINTEF Energy, Trondheim, NORWAY, sverre.hvidsten@sintef.no, hallvard.faremo@sintef.no Wet designs of XLPE cables, meaning cables without any impervious water barrier, have been frequently used for MV applications. However, past experience revealed that water treeing were attributed to these types of XLPE cables, contributing to a faster electrical degradation and shorter lifetime compared to dry designs. During time and intensive research, there was consensus about that the major contribution to water treeing depended on the quality of the insulation system and vulcanization process used. Experienced cable manufacturers of today have the latest 10-20 years improved both vulcanization processes, material handling systems and quality of materials to a degree far better the level which was prevailing 30 years ago or more. Today MV cables are normally designed without water barriers but with longitudinal water tight materials in conductors. Since good operating experiences have been seen one could therefore ask if wet designs are mature to be introduced also at HV (52 - 170kV). To answer this question, a test and modelling program has been implemented at Sintef and Nexans in Norway. There is no standardized test method for water aging tests at HV but aging tests according to Cenelec-500 Hz has been scaled up and slightly modified for HV. Using high-quality materials and processes good results have been obtained for HV cables. In addition, several tests of small cable samples have been put in water baths at different temperatures and for different durations to establish a good estimate of water saturation and water content levels in different layers of a specific wet design to be used in a HV dynamic application in North Sea. These data in combination with accurate characterization of cable materials have been put into a water diffusion model taking into account also temperature drops across different cable layers etc. It has been seen that only a small temperature drop across an outer plastic sheath is sufficient to effectively prevent the water content to exceed RH99%, thus reducing the rate of growth of water trees from the outer semicon layer. The tests and computation models presented in this paper give confidence that wet designs could be introduced at low risk in certain applications for HV cables. However, the conditions for such a direction are high quality control in materials and processes and a thorough test and quality plan how to verify such an approach to be confident. Water trees are developed under certain types of conditions. However, if the effect of some conditions are reduced or even eliminated for both MV and HV applications, it is very likely that past comprehended risks of water treeing, need a reevaluation conditioned by the high quality materials and processes used today. Key words Wet design, water barrier, Cenelec, water aging test, 500 Hz, power cables, JICABLE15_0199.docx Fracture behavior and thermo-oxidative ageing of EPDM Christopher KARTOUT (1, 2), Antonella CRISTIANO-TASSI (1), Grégory MARQUE (1), Costantino CRETON (2) 1 - EDF R&D, Mechanical and Materials Components Department, Ecuelles, France, christopher.kartout@edf.fr, antonella.cristiano-tassi@edf.fr, gregory.marque@edf.fr 2 - ESPCI, SIMM, Paris, France, costantino.creton@espci.fr Insulating materials of LOCA qualified electric cables in nuclear power plants are constituted by rubbers having good ageing resistance properties, like ethylene and propylene copolymers (EPR, EPDM …), to ensure the conductive material. In service these cables are submitted to low irradiation and temperatures that could reach 50°C in the reactor building. The prediction of the life time and the control of cables properties by innovative and non destructive methods are the aims of numerous experimental and numerical studies at EDF R&D. An accelerated thermal ageing has been applied to model materials, constituted by an EPDM matrix filled with different proportions of aluminum trihydrate fillers (ATH), some of them having a surface treatment to improve the adhesion between the EPDM matrix and the fillers. It has been observed that the main consequence of the thermal ageing is a chain scission phenomenon identified by: a decrease of the elastic modulus, obtained by tensile tests, an increase of the degree of swelling and of the sol fractions (in xylene), and an increase of the chains network mobility, characterized by 1H NMR. The consequences of this thermal degradation on the viscoelastic behavior have been studied by DMA and cyclic tensile tests. Finally, infrared spectroscopy has confirmed the oxidation due to thermal ageing, showing the formation of carbonyls and hydroxyls species, which are the both main oxidative products of the carbonated chains of polyolefin. The study of materials with different filler proportions pointed out that higher amount of fillers lead to a decrease of the ageing consequences on the properties of the networks. The results obtained with the materials containing surface treated fillers show that the ATH/matrix interface may be deteriorated. Finally, crack propagation measurements under cyclic loadings have been done on pre-crack pureshear samples and have showed that the thermal ageing leads to an increase of the crack growth rate at constant energy release rate. The cracking tests may offer the possibility to link the elongation at break of the elastomer with its crosslink density, by comparing the energy needed to reach the failure in uniaxial tensile tests (nowadays used to predict the life time of cables) and the energy release rate needed to propagate a crack in cyclic tensile tests. The oxidation state, and therefore the crosslinking of the network will be related to the needed energy. JICABLE15_0200.doc Efficient project management of high voltage underground cable systems against self-evident facts Michel DUBREUIL, Hervé POMBOURCQ (1) 1 - RTE, Paris, France, michel.dubreuil@rte-france.com, herve.pombourcq@rte-france.com ENGINEER. The first early job in the career of a young man. Knows anything about science. (Gustave FLAUBERT, Le dictionnaire des idées reçues / The dictionary of accepted ideas). The selection of underground techniques for a high voltage power link must not lead inexorably to bury one’s own common sense. When exercising his art, the engineer must not give in to the temptation of the apparent easy solutions of preconceived ideas. The increasing use of underground cable systems is often based on the argument of the easy acceptance by the people living in the neighbourhood, compared with the overhead line scenario. Hence a project manager may be inclined to believe it is more straightforward to succeed in an efficient project with underground techniques, whether in terms of technical optimisation, deadlines, costs or environmental impact. This is not the case at all: to make such a project efficient, it is necessary to be aware of and to integrate the constraints, opportunities and limits of the underground cable solution. From the early decision-making studies to the comprehensive detailed reviews, every option of the project must be enlightened by the analysis of its possible resulting impact, less obvious on the global performance. The parameters which have a significant influence on the scope, cost and impact of an underground power link project are actually numerous. Some of them seem trifling: The selection of one cable route or another (larger or smaller, more or less congested with other buried networks), The mutual presence of other electrical underground links in operation, The vicinity of other underground infrastructures, The crossing within other routes (roads, highways, railways, structures as bridges, etc), The methods of civil works and installation, the geometry of conductor laying, The nature and quality of soil, Topography, The location of joint bays, The scheduled season of achievement, The interference with other works, Etc. In order to prevent from any drift, it is therefore essential to clearly identify and to control these topics and their potential repercussions. The authors discuss this approach in the present paper. JICABLE15_0201.doc Fiber optic temperature sensor using intermodal interference for linear infrastructures monitoring. Frédéric MUSIN (1), Patrice MEGRET (1), Henri GRANDJEAN (2), Jan CALLEMEYN (3), JeanChristophe FOHAL (3), Marc WUILPART (1) 1 - University of Mons - FPMs - SET, Mons, Belgium, frederic.musin@umons.ac.be, patrice.megret@umons.ac.be, marc.wuilpart@umons.ac.be 2 - ORES, Louvain-la-Neuve, Belgium, henri.Grandjean@ores.net 3 - CERISIC, Mons, Belgium, jan.callemeyn@cerisic.be, jean-christophe.fohal@cerisic.be Asset management for electricity transmission system operators (TSO) pushes the need for intensive cable and substation monitoring to protect investments, guarantee supply in safe conditions and optimize the lifetime. In this context, temperature monitoring plays a key role to check sizing, installing techniques effectiveness and cable power capacity in its underground environment. Two measuring approaches are already on the market to meet all TSO's requirements at different cost level: local and distributed sensing. The localized approaches use point sensing for strategic control like in cable joints at an affordable cost. Their efficiency is proven but in case of a fault appearing in an unmonitored zone, the network operator will not be warned. It is clear that point sensing does not enable a complete awareness of the performance and state of the infrastructure. On the other hand, the distributed approach offers a wide range of opportunities using distributed network of sensors (quasi-distributed approach) or a continuous sensor (fully distributed approach) but is very costly. With this technique, the state of the whole infrastructure can be assessed and faulty conditions can be detected anywhere in the structure. Fiber optic-based measurement techniques are widely used for quasi-distributed and distributed temperature sensing and present some advantages like electrical insulation, low-loss transmission and high sensitivity. Commercial solutions for distributed fiber optic temperature sensing are available on the market but are mainly focused on electricity production and transport due to their high cost. In this context, we have developed a low-cost fiber optic temperature sensor technique especially designed to meet electricity distribution needs. This quasi-distributed sensor measures temperature deviation all along a fiber and allows for hazardous conditions detection. Based on intermodal interference pattern analysis, the technique is sensitive enough to detect joint failures and soil drying scenarios. This paper presents the results of the proposed technique applied to the monitoring of TYCO MXSU 95-240mm² joints. The validation is achieved by comparing the conventional and optical measurement techniques when estimating the thermal behavior of industrial electrical junctions of good and bad quality. The possible extension of the technique with fully distributed functionality is finally introduced. Key words Optical fiber sensor, distributed thermal sensing, intermodal interference pattern, image processing. JICABLE15_0202.docx Rejuvenation of EPR-insulated medium voltage underground cables Richard VARJIAN (1), David BUSBY (1), Glen BERTINI (1) 1 - Novinium, Inc, Auburn, Washington, USA, richard.varjian@novinium.com , david.busby@novinium.com , glen.bertini@novinium.com The technical case for rejuvenation of underground medium voltage polyethylene cables (PE) has been established for some time.(1,2) The dielectric strength of PE is degraded over time due to strong oxidants formed from water in a medium voltage AC electric field. The oxidants attack the polymer backbone leaving behind structures known as water trees. The reduction in dielectric strength associated with water trees and their role in space charge injection makes them precursors to electrical trees and faults. Current generation rejuvenation fluids react with and remove water leaving behind a short liquid polymer that restores the dielectric strength of PE insulation. The technical case for rejuvenation of underground medium voltage cables with ethylene-propylene rubber (EPR) insulation has not been accepted universally for several reasons: EPR-insulated cables generally have enjoyed a higher in-service reliability compared to vintage PE cables Water trees are fewer in number and/or more difficult to detect than those in PE cables The paucity of water trees in EPR insulation makes their role in electrical failures more controversial EPR is a complex, composite material whose composition varies by manufacturer. These factors make it difficult to relate laboratory results to field experience and to apply laboratory results commonly to all EPR cables. The authors’ firm has applied its rejuvenation treatment to a sufficient number of EPR-insulated medium voltage cables in North America to provide field performance data for EPR rejuvenation. Field data is available for over 3 million meters of underground medium voltage electrical cables of all types. The vast majority has been PE cables originally installed in the 1970’s and ‘80’s. Approximately 7.5% or 225,000 meters of the total has been insulated with EPR. The post-rejuvenation cumulative failure rate for the two types of insulation is nearly equal, 0.4%. The chemical structures of PE and EP base polymers are very similar. The backbone is a saturated hydrocarbon. The water induced oxidation mechanism and polymer-protective-additives such as antioxidants apply to both polymeric materials. Additionally, silanes similar to those used in current generation rejuvenation fluids, added in minor amounts to EPR compositions, have been shown to be beneficial to electrical property retention.(3) In general, failures and lifetime limitations are related to loss of protective additives through oxidation or transport out of the material. Some proprietary rejuvenation fluid formulations contain water reactive alkoxy-silanes, anti-oxidants and other additives which replenish the depleted cache in the aged insulation. The paper describes the rejuvenation process as applied to EPR cables, discusses the available field data in more depth and more fully outlines the nexus between generic EPR compositions and rejuvenation additives. Precautions for applying rejuvenation to EPR-insulated cables are discussed as well. References 1) C Katz, et al., “Influence of Water on Dielectric Strength and Rejuvenation of In-Service Aged URD Cables,” Proceedings of Jicable 84, pp172-174 (1984). 2) MT Shaw and SH Shaw, “Water Treeing in Solid Dielectrics,” IEEE Transactions on Electrical Insulation, vEI-19, pp419-452 (1984). 3) B Ohm, et al., “Compounding EPDM for Heat Resistance,” Rubber World, August Issue, pp3337 (2002). JICABLE E15_0203.do ocx Resilient 12 to 36kV V touch safe aerial netw work so olution with w a comp petitive Total T Co ost of O Ownersh hip Lars EFR RAIMSSON,, Ingvar HAG GMAN, Johan n ÅHMAN 1 - nkt ca ables AB, Fa alun; Sweden n, email: larss.efraimsson@ @nktcables.com, ingvar.ha agman@nktccables.com, johan.ahma an@nktcable es.com This sysstem has be een develop ped in respo onse to utiliities demand ds for moree efficient in nstallation methodss, cost savin ngs and inc creased relia ability. The fully insulatted aerial caables offers s a more profitable e long-term investment by b reducing ccosts for righ ht of way, bu uilding, mainntenance and d causing less pow wer interruptio ons. The con nstruction re duces repairr down time in comparisoon with otherr systems - resultin ng in less rep pair call-outs s and smooth h maintenan nce. In generral the dangeer due to exp posure to live liness is removed. Fig 1 Ca able suspenssion clamp an nd dead-end d fixing helica al The robu ust constructtion of the fully insulated cable system m offers seve eral significaant savings by b greater freedom and flexibilitty of line routting. It can b e routed ove erhead, in the e ground, unnderwater, orr adjacent to trees. For aerial in nstallation, th he cable man nages even long span len ngths. Thesee multipurpos se cables are also powering railways and supplying s pow wer to mines s through verrtical drilled hholes. e as aerial an nd ground ca able Fig 2 Use Fig 3 Joint installation Fig 4 Steep rise JICABLE E15_0203.do ocx Fig 5-6 C Cable from air into a subsstation Fig 7 Trees on ccable after sttorm The overrall project execution e tim mes are shortter and more e cost effective. This incluudes all phases, from concession, planning g, layout an nd design, aand finally during d building of the innsulated aerrial cable system. ple: a cost effective e wayy to upgrade an existing transmissionn line is to install the An illustrrative examp insulated d cable syste em beneath the air insulaated bare co onductor tran nsmission linne, which can n be kept in full op peration. Tra ansfer of pow wer to the ccable system m requires ass a maximum m only a few w minutes power o outage. Tem mporary pow wer during b building of the t new line e is conseqquently not required. After rem moval of the old conducto ors, the fullyy insulated ca able can be elevated e live on line. In otherr applicationss fully insula ated aerial caables have been b built in n parallel witth the LV lin nes which needed u upgrading du ue to overloa ad or voltagee drop issuess. Powering g the electriical grid with fully insul ated aerial cables provides a lowerr TCO (Total Cost of Ownersh hip) than air insulated ba are lines. Th he improved service - no o loss of suppply for custtomers in vegetatio on dense arreas also me ean cost savvings for utilities. The cable solutionn results in excellent safety - a fully insu ulated, screened robust cable is safe e for mainte enance as w well as for vegetation ment crews and a last but not least thee local reside ents. managem Galloping g waves and d vibration arre no issues ffor these cab ble lines as documented d nology on by EA-Techn their She etland Island d test site. JICABLE15_0204.docx Long power cables: exposing incipient faults and optimizing performance using extra-long fiber optic distributed temperature monitoring. Etienne ROCHAT(1), Marc NIKLES (1), Baz MATVICHUK (1), Jane ROWSELL(1) 1 - Omnisens, Morges, Switzerland er@omnisens.com, mn@omnisens.com, bm@omnisens.com, jr@omnisens.com Monitoring the temperature of power cables continuously all along their length provides condition monitoring and the opportunity for cable performance optimization using dynamic cable rating. However critical infrastructures being built or planned for the coming years, such as distant offshore wind farms (more than 60 km from the coast), ambitious interconnector projects and the growing preference for undergrounding require high performance, efficient asset management with reliable condition monitoring, whilst their length challenges the distance limits of existing temperature monitoring techniques. At the same time monitoring the temperature of cables is becoming more critical due to the potential risks from: Reducing conductor diameter in order to lower the cost and the weight of long submarine cables. Exposure of buried wind farm array and export cables which could compromise the environment in addition to threatening their integrity due to absence of physical support. Changing seabed conditions which will affect the thermal condition of the cables and accelerate the cable ageing process. Dropped items and anchor drag in the often shallow waters where wind farms are built. Further, floating wind farm cables will face challenges similar to those experienced by subsea power umbilicals used in offshore oil & gas production, with the potential for unseen abrasion at touchdown points and thermal bottlenecks under areas with foam protection or under mattresses/rock dumps. Distributed temperature monitoring using fiber optic-based distributed sensing contributes to the safe and efficient operation of many onshore transmission cables and subsea cables. Extending these benefits cost effectively to longer array, export, interconnector and onshore transmission cables can be met using Brillouin-based sensing, which has demonstrated distributed sensing capabilities over more than 300 km from one interrogator, while maintaining temperature measurement performance in terms of both spatial and temperature resolution. This papers, referring to proprietary research and supported by several Case Studies shows how Brillouin distributed monitoring can be configured from a single interrogator or using remote switch operation, amplifiers and repeaters to provide cost effective temperature monitoring of long cables, on and offshore. Case studies includes the monitoring of an interconnector, long onshore cable and wind farm export cables such Walney Offshore Windfarm 1 & 2 (>50 km), Greater Gabbard Offshore Windfarm (> 65 km), London Array Offshore Windfarm (> 70 km). Key words: DTS, cable temperature, dynamic cable rating, condition monitor, cable performance , subsea cable, buried cable, array cable, export cable, interconnector JICABLE15_0205.doc Validation of a generic tool of kinetic simulation of cable ageing Mouna BEN HASSINE (1), Romain MAURIN (1) and Gregory MARQUE (1) 1 - EDF R&D, Matériaux et Mécanique des Composants (MMC), avenue des Renardières avenue des Renardières, F-77818 Moret-sur-Loing, France, mouna.ben-hassine@edf.fr, romain.maurin@edf.fr , gregory.marque@edf.fr. Since the early 2000s, the EDF R&D team of polymers is interested in the study of the multiscale analysis aging of polymers (at the molecular, macromolecular and macroscopic levels) used in nuclear power plants, such as cables, pipes or paintings [1-4]. This understanding of the mechanisms of aging allows, among others, to develop a universal approach for life time prediction or monitoring the aging of these materials on-site. The establishment of structure/property relationships remains the major problematic in any non-empirical approach for lifetime prediction. The objective of the present work is to present the first step of this approach which is the development of a generic tool of simulation of aging kinetics and its validation on different ethylenic polymers (EPDM and PE) used in cables. The approach taken to establish the physical model validation of polymer aging consists in: First, the integration of a system of non-linear differential equations derived from an established mechanistic scheme for describing the polymer ageing process in the simulation code. Then, the comparison of chemical experimental results [1,5] (obtained by FTIR spectrophotometry in a transmission mode to deduce changes in concentration of thermal degradation products) and numerical resolution (obtained both with Matlab software and the new simulation tool) (Fig.1). Fig. 1: Comparison of carbonyl evolution results obtained both with Matlab software and the new simulation tool. The results show a satisfactory agreement between theory and experiment in a wide temperature range. Thus, this new developed simulation tool is validated on well-controlled tests and allows us to take with confidence the next step of our approach for lifetime prediction, i.e. the prediction of macromolecular and macroscopic changes of polymer and the proposed methodology is conceptually applicable to other types of polymer. References [1] N. Khelidj, «Vieillissement d'isolants de câbles en polyéthylène en ambiance nucléaire», PhD thesis, 2006- ParisTech. [2] Y. Zahra, « Influence de la structure du réseau époxyde en ambiance nucléaire», PhD thesis, 2012-Paristech. JICABLE15_0205.doc [3] A. Shabani, «Vieillissement thermique et radiochimique de matrices EPDM pures et chargées d’ATH: Mise au point de relations structure/propriétés», PhD thesis, 2013 ParisTech. [4] A. De Almeida, «Propriétés mécaniques et dégradation des élastomères EPDM chargés ATH», PhD Thesis, 2014-INSA Lyon. [5] M. Ben Hassine, «Modélisation du vieillissement thermique et mécanique d’une protection externe en EPDM de jonctions rétractables à froid», PhD thesis, 2013-ParisTech. JICABLE15_0206.docx Thermo-mechanical behavior of HV and EHV large conductor XLPE cables in duct-manhole systems Stephen ECKROAD (1), Tiebin ZHAO (2), Stephen J GALLOWAY (3), Brian GREGORY (3), Stephen M KING (4) 1 - Electric Power Research Institute, Palo Alto, USA, seckroad@epri.com 2 - Electric Power Research Institute, Charlotte, USA, tzhao@epri.com 3 - Cable Consulting International Ltd, Sevenoaks, UK, stephen.galloway@cableconsulting.net, brian.gregory@cableconsulting.net 4 - Dassault Systemes UK Ltd, Sevenoaks, UK, stephen.king@3ds.com This paper describes the continued research work by EPRI (the Electric Power Research Institute) on the thermo-mechanical behavior of large conductor cables in duct-manhole systems. Transmission Class XLPE insulated cables with large conductor sizes up to 2500 mm2 are being installed in duct-manhole systems in North America. The duct-manhole system has well proven advantages of minimum disruption to traffic in busy urban roads. Duct-manholes are thermomechanically classified as semi-flexible systems. Duct systems can be designed to alleviate the magnitude of axial thrust acting on joints at manhole positions. Provision is made in the selection of the duct diameter for the sideways movement of the thermally expanded cable to permit it to form thermo-mechanical patterns and so absorb a proportion of the thermal strain. In CIGRE paper B1-111, 2006, EPRI describes two design methods to i) calculate the magnitude of the axial force and ii) constrain the joint within the manhole. These used mechanical parameters extrapolated from those measured on small conductor size cables, these being a 138kV 750 mm2 copper tape screen and a 230kV 1250 mm2 lead sheathed design. Since 2006 EPRI has used advanced FEA modeling techniques to design and construct a 59m long test rig to simulate the full sized performance of cables in duct systems and to quantify the thermomechanical performance of large conductor EHV cables. This paper describes the formative FEA modeling work for the design of the test rig and the commissioning of the rig with a 345kV, 2000 mm2 copper conductor, XLPE insulated, corrugated aluminum sheathed cable. The rig is designed to i) measure the magnitude of the axial force at each end of the cable sample rig and ii) record the shape of the thermo-mechanical cable patterns, both quantitatively by measuring the transverse position of the cable at one metre intervals along the length and visually by opening four inspection hatches positioned along the rig. A study is made of the effective magnitude of the cable thermo-mechanical parameters e.g. cable axial stiffness EA, bending stiffness EI, axial stiffness JI and coefficient of thermal expansion. The key findings for large conductor cables in duct-manhole installations are that i) the magnitude of axial force is lower than extrapolated from smaller conductor cables and ii) thermo-mechanical patterns form, but are less pronounced in the magnitude of lateral deflection. JICABLE15_0207.doc Key properties of next generation XLPE insulation material for HVDC cables Villgot ENGLUND, Johan ANDERSSON, Virginie ERIKSSON, Per-Ola HAGSTRAND, Wendy LOYENS, Ulf H. NILSSON, Annika SMEDBERG 1 - Borealis AB, Stenungsund, Sweden, villgot.englund@borealisgroup.com, carljohan.andersson@borealisgroup.com, virginie.eriksson@borealisgroup.com, per-ola.hagstrand@borealisgroup.com, wendy.loyens@borealisgroup.com, ulf.nilsson@borealisgroup.com, annika.smedberg@borealisgroup.com The installation of HVDC transmission systems has over the last decades grown substantially, especially during the last five years. The driving force for the increased penetration of HVDC links in the network has mainly been governed by the switch to renewable resources, where the generation predominantly is situated far from the use of energy. This growth is projected to continue. In addition, interconnections to strengthen the existing AC grids with bulk transmission of energy over longer distances are needed, which is only achievable with DC. This is to secure the reliability of the network and improve the energy market. Not all these new transmissions lines will be made with cables, however to facilitate shorter lead times for concessions, partly undergrounding with cables is more and more an attractive solution. For over 15 years it has been possible to use extruded HVDC cables to transmit power over longer distances. The recent development of a new unfilled cross-linkable material has enabled the use of extrudable HVDC cables rated at 525kV. The new material solution is based on a known technology platform, building on the extensive experience in producing specialized compounds for the highest requirements. However, for the development of insulating materials to be used in cables for HVDC transmission above 320kV, a new way of thinking in terms of contamination was needed - i.e. there was a need for higher chemical cleanliness. Besides the well-known physical cleanliness i.e. minimization of solid particles giving rise to field enhancement, known since decades from the world of AC materials also the chemical cleanliness is of importance. This is characterized by the minimization of species that can contribute negatively on the molecular level to key electrical properties such as DC conductivity. This paper will present the outcome from the recent development including an in depth analysis of the key material properties such as DC conductivity which are needed to reach HVDC transmission at extra high voltage level. It was found that the improvement of the chemical cleanliness together with optimization of the material composition resulted in a significant reduction of the DC conductivity. This, in turn, has allowed successful type test qualification at 525kV according to Cigre TB 496 recommendation (for voltages up to 500kV). The material shows, furthermore, various interesting processing benefits, compared to a conventional cross-linkable polyethylene. JICABLE15_0208.doc Development of a 345kV XLPE extruded cable for HVDC applications Marie-Laure PAUPARDIN (1), Mohamed MAMMERI (1) 1 - GENERAL CABLE, Montereau France, mlpaupardin@generalcable-fr.com, mmammeri@generalcable-fr.com For many years, there is a strong attraction in the use of submarine and underground for high voltage direct current (HVDC) cables. This request involves the cable and accessories qualification whose voltage level rises gradually with market demand. The choice of extruded cable reinforces this growing interest in achieving high voltage links without maintenance and low impact for environment. The first developments were performed for voltage level ranging from 270kV up to 320kV and recent on 345kV. This technical study presents a test of qualification for this voltage level with both LCC and VSC technology. This voltage increasing is due to an understanding of space charge formation and behavior under direct current stress. The electric field distribution modeling, the choosing of right materials and appropriate design accessories allow achieving these results. The tested cable is a 2500mm² aluminum conductor with extruded insulation of 21.5mm thickness. The loops include accessories with molded and premoulded joints and composite outdoor terminations. The electrical test has been performed according to the technical brochure Cigré n°496 combining the VSC and LCC protocols for electrical test which recommend type test and prequalification test. VSC technology, the most used with extruded cable, is based on the principle of the power flow reversal by not changing cable polarity. The cable system passed successfully the tests for the nominal voltage U=345kV. The interest of this double qualification is to show that the cable system can be used independently of the conversion technology chosen. This also proves the reliability of the cable system by allowing the change in the link operating. The authors will present the main characteristics of the system and the detail of electrical tests results. Keywords: HVDC, 345kV, LCC, VSC, TB 496, extruded cable JICABLE15_0209.docx Heat dissipation of high voltage cable systems - A technical and agricultural study Jan BRÜGGMANN (1), Ludger JUNGNITZ (1), Peter TRÜBY (2), Dirk UTHER (1) 1 - Amprion GmbH, Dortmund, Germany, jan.brueggmann@amprion.net, ludger.jungnitz@amprion.net, dirk.uther@amprion.net, 2 - Albert-Ludwigs-Universität, Freiburg, Germany, peter.trueby@bodenkunde.uni-freiburg.de . Germany is going to restructure its whole energy sector within the framework of the so called “Energiewende”. Due to the fact that wind energy and especially off-shore wind farms are located in the North of Germany, there is the need to strengthen the North-South transport capacity of the electricity network. To increase the overall public acceptance of electrical infrastructure certain projects were identified by the government and given by law, where partial cabling at 380kV AC shall be implemented as pilot projects to gain experience. An important aspect in designing these cable systems is the bedding material. It influences the ampacity significantly. For cable links of smaller transmission capacity, sand was applied and rated to be sufficient. Due to the increasing transmission requirements, accompanied by increasing ohmic losses and thus increased emitted heat, there was the need to look for bedding materials with lower risk of partial drying. The analysis of possible alternatives turned out, that in general, there are materials available fulfilling the more advanced technical requirements. Among those were promising new bedding materials. However there was the lack of experience concerning the behavior of this new type of bedding material that showed up strength and weaknesses under laboratory conditions. To qualify these new betting materials it was decided to launch a field test under life conditions and to investigate the thermal properties in detail. Therefore, a new build cable system with a length of about 400 m was equipped with various bedding materials. The applied materials were chosen with respect to their expected performance as well as their acceptance by permitting authorities and landowners. As a second, not less important aim was to gain insight about the influence of the cable system as a heat source on the performance of soil used for agricultural purposes covering the cable route. Therefore, the vicinity of the cable system was equipped with temperature and moisture probes. Right above the cable system, different agricultural crops were cultivated. The harvest from the cable route was compared to the one of a reference field nearby. The test setup including the cable system, the bedding materials, the circuit to heat up the system artificially as well as the arrangement of temperature and moisture probes will be explained. An analysis of the thermal distribution with respect to the applied bedding material and its shape will be provided. The results of different harvests will be displayed. JICABLE15_0210.doc Identification of cable local thermal stress with time domain reflectometry. Thierry ESPILIT (1), Jean Marie FAGEON (2), Sandrine FRANCOIS (3) 1 - EDF R&D, Moret sur Loing, France, thierry.espilit@edf.fr, 2 - EDF DPN, Paris, France, jean-marie.fageon@edf.fr 3 - EDF SEPTEN, Lyon, France, sandrine.francois@edf.fr Studies on insulation resistance decrease that have been observed on certain single core MV PVC insulated cable showed a behavior closely related to the thermal history of the cables.Ageing test showed that, even after a long period of application, steady constraints led to very low evolution of the resistivity. As considered cables are operated in very stable condition, no preventive replacement is needed. Nevertheless, as cable insulation characteristics appeared very thermo sensitive, the very unlikely hypothesis of a local thermal constraint had been considered. So, possibility for identifying such a constraint applied with onsite electrical measurements had been studied and results are presented in this paper. Lab test were performed on single core MV cable removed from network after more than 20 years of operation. Samples on cables with low values of resistivity were focused. Heated Zone / different temperature Experiments showed that local constraint could be identified by time domain reflectometry (TDR). Then the physical reason have to be clearly defined in order to precise the relation between high frequency electrical characteristics versus thermal constraint. Results of dielectric spectroscopy characterization of thermal behavior had been analyzed in order to identify the main physical parameter involved. Then, impedance changes detected by TDR had been most likely attributed to differential radial dilation. EMTP simulation showed that reflected signal amplitude could be very important even very small geometrical changes occurs as a consequence of differential dilatation. Dielectric spectroscopy characterization is used to model thermal dependence of electrical characteristics on a large frequency range. First results are presented. Works have to be completed in order to define accurate decision criteria for a non destructive control method but industrial application foreseen to identify thermal constraint is presented. Results are also usefully applied to explain impedance change observed in PD measurements. JICABLE E15_0211.do ocx High safety y and low m maintena ance ae erial ca able sy ystem withs standing g extrem me weath her Lars EFR RAIMSSON,, Ingvar HAG GMAN, Jan K KÖHLER, Hå åkan BRINGSELL 1 - nkt ca ables AB, Fa alun; Sweden n, email: larss.efraimsson@ @nktcables.com, ingvar.ha agman@nktccables.com, jan.kohler@ @nktcables.co om, hakan.brringsell@nkttcables.com Today, w we are completely depe endent on ha aving access s to electrica al power. Ouutages on th he power supply can quickly ha ave severe consequence c es. And it will be expensiv ve for the enntire commun nity. In 2012, the costs we ere estimated at nearly 1 billion SEK almost 100 million m Euro - in Sweden alone. A system has been n developed d in respon se to utilitie es demands s to withstannd extreme weather condition ns without po ower interrup ption. The un nique design n can handle e.g. ice loadds, storms and snowladen tre ees. The self-supporting conductors take up the bulk of the tensile stresss. The force es from a falling tre ee are prope elled through the cable sh heath and ins sulation into the supportinng conductor, without damagin ng the cable. This reduc ces repair do own time in comparison with other ssystems - resulting in less repa air call-outs and a smooth maintenance e. Fig 1 Snow S cowere ed heavy bra anches on live cable ust constructtion of the fully insulated cable system m offers seve eral significaant savings by b greater The robu freedom and flexibilitty of line routing. There iss no risk for power outag ge caused byy falling trees s or birds causing short circuit as compared to bare lines. Risks s of direct lightning striikes are also greatly reduced compared with w bare wire lines, with h the fully in nsulated cable not attraccting lightning strikes, and indiirect strikes causing no damage to o cables. Th here are also o reduced liightning pro oblems at OHL/und derground ca able transitions. Other be enefits of the e fully insulatted cable sysstem are rarre power cuts s as a resultt of broken line wires, and envvironmental hazards h such h as sand, ssalt and cond ducting dustt (may causee fires). Con nventional bare line e systems arre prone to short s circuitss due to clas shing conduc ctors, whereeas the fully insulated system ccomprises off one fully ins sulated cable e, and thereffore completely eliminatees this proble em. Tests on Shetlland islands and installations in Norw way have prroven that ga alloping and vibration no ot to be a problem. As a ressult of the ab bove, fewer repair call-o uts are requ uired for the fully insulateed cable sys stem, and there is a reduced nu umber of diffficult repair a and clearing line jobs. Em mergency calll out are nott needed, Clearing g of lines can be performe ed during norrmal working g hours. JICABLE E15_0211.do ocx Fig 2 Heavy H tree on live cable Fig 3 Trees on livee cable afterr storm JICABLE15_0212.docx Transient thermal phenomenon in HVDC extruded cables under test and operating condition - numerical simulation and measurements Christian FROHNE (1), Johan KARLSTRAND (2), Marie-Helene LUTON (3), 1 - Nexans Deutschland GmbH, Hannover, Germany, Christian.frohne@nexans.com 2 - JK Cablegrid Consulting AB, Karlskrona, Sweden, karlstrand@cablegrid.com 3 - Nexans France, Calais, France, Marie_Helene.luton@nexans.com Due to the temperature dependency of the DC conductivity of extruded insulation materials, the test and operation condition need to be carefully selected with respect to their thermal condition. The thermal environment has an impact to field enhancement resulting from the thermal gradient in the insulation. Optimizations in the thermal setup of the test loop to reduce this temperature gradient during test condition, can lead to premature thermal instability. Common practice of temperature control during HV cable testing is the parallel operation of two cable loops, where one loop is used as thermal reference and is equipped with temperatures sensors on the cable surface and the cable conductor, while the cable loop under voltage is monitored for surface temperature only. In this paper a SPICE (Simulation Program with Integrated Circuit Emphasis) model is presented, which simulates the thermal behavior of both loops. The network simulating the loop for temperature monitoring consist of resistors and capacitors simulating the thermal properties of the cable and the cable environment as well as the heating source from conductor heating. The model of the loop under voltage consist of a parallel network in the structure as above to simulate the thermal behavior, and a parallel network, which simulates the electrical field distribution and leakage current in the insulation. The electrical network and the thermal network of the cable loop under voltage are linked to each other via power loss density from leakage current and temperature influence on conductivity. Different methods of applying thermal insulation and temperature monitoring during qualification tests are compared with respect to their risk of premature thermal instability and their influence on field enhancement from temperature gradient. Temperature measurements on real test setups of 320kV cable system are compared with the simulation results. Insulation leakage current is evaluated based on leakage current measurement and thermal observations on the test cables under voltage. The insulation resistivity calculated back from the measurements on the cable section is compared with material properties determined on small scale samples. With the calibrated model from this observation a typical cable installation is simulated with respect to thermal behavior and risk of thermal instability. JICABLE15_0213.doc Aging assessment of cable insulation used in nuclear power plants through electrical measurements: the lesson learnt from the ADVANCE EU project Davide FABIANI (1), Luca VERARDI (1), Gian Carlo MONTANARI (1), Christophe MOREAU (2) 1 - DEI- University of Bologna, Bologna, Italy, davide.fabiani@unibo.it, luca.verardi@unibo.it, giancarlo.montanari@unibo.it 2 - EDF R&D, Moret sur Loing, France, christophe.moreau@edf.fr Nuclear power plant (NPP) facilities rely on several hundred kilometers of low-voltage instrumentation, control and power cables. Many of these cables are installed in the containment area, where the harshest environmental conditions, characterized by high temperature and gamma-radiation, can stress significantly cable insulations. Under the combined effect of temperature and radiation, in fact, the polymers used for cable insulation and jacket materials are subjected to degradation, e.g. oxidation, polymer chain scissions and free radical formation. This degradation, activated by temperature and radiation, cause polymers to become more and more brittle, thus no more useful as cable electrical insulation which requires good thermal, mechanical and electrical endurance. The assessment of the aging condition of these cables is of utmost importance as the basis for life extension of nuclear power plants, with particular attention for the cables, which must directly support the safe operation of the facility. Those cables, in fact, must present acceptable mechanical and thermal properties during all their life, since they have to withstand very hard conditions as those occurring in loss of cooling accidents (LOCA). Nowadays, the integrity and functionality of these cables are monitored through destructive testing by measuring chemical properties, such as OIT, OITP, TGA, and mechanical properties, e.g. elongation at break. According to these quantities, detailed guidelines for testing and aging evaluation are provided, e.g. in IEC Std. 60544. The investigation of electrical aging markers which can provide information on the state of the cable by non-destructive testing methods would improve significantly the present diagnostic techniques. Literature regarding the effect of aging on electrical properties of low voltage insulation is still lacking. A few techniques, in fact, were investigated focusing on low voltage cables, e. g. LIRA, TDR, Voltage Return, loss factor. This topic is being investigated within the European Project ADVANCE “Ageing Diagnostics and Prognostics of low-voltage I&C cables”. The search of aging markers coming from electrical properties like, e.g., electrical conductivity and dielectric spectroscopy, to assess the state of low voltage cable insulation, is the purpose of this paper. In particular, test results of electrical property measurements on EPR, XLPE and EVA insulations used for power cables of NPPs. These cables were aged under thermal and radiation stresses: in order to obtain significant results in a reasonable time, the dose rate and the temperature chosen were higher than the values usually found inside NPPs. These measurements have been performed using dielectric spectroscopy, which allow the real and imaginary part of the permittivity in the frequency domain to be obtained. The change of electrical properties with aging was correlated to variation of elongation-at-break and chemical properties (density and gel fraction). For most cables, a good correlation was found, in particular, between imaginary part of the permittivity at 100 kHz and density measurements, which indicated oxidation as the main degradation mechanism. Therefore, the imaginary part of permittivity at high frequency, could be an interesting non-destructive property to assess the degradation state of NPP cable insulation. JICABLE15_0214.doc Off-line Diagnostic Measurements: Type of Measurement versus Insulation Weakness Targeted. Thierry ESPILIT (1), Jean François DRAPEAU (2), Sverre HVIDSEN (3), Roger TAMBRUN (4), 1 - EDF R&D, Moret sur Loing, France, thierry.espilit@edf.fr 2 - IREQ, Varennes, Canada, drapeau.jean-francois@ireq.ca 3 - SINTEF Energy Research, Norway, Sverre.Hvidsten@sintef.no, 4 - ERDF, Paris La Défense, France, roger.tambrun@erdfdistribution.fr In Europe off-line MV cable diagnostic methods have been widely used by utilities in order to help underground network asset management to take the best possible replacement time decisions. Even if on-line assessments are targeted for future applications, off-line methods are actually very useful and sometimes preferable to identify certain defects. EDF R&D, SINTEF and IREQ are laboratories that have for a long time been involved in evaluating diagnostic methods and editing guidelines for diagnostic methods and criteria to be used by national utilities networks, according to their specific needs. This paper intends to summarize some of the work performed by the three laboratories in order to present a convergent approach of the use of available diagnostic tools. The aim of this paper is to give an objective and clearer idea of what could be achieved with the different measurement methods used today in terms of identifying cable systems defects limiting the service life. The two main aspects of diagnostic applications, i.e. technical and economical, will be addressed. The technical challenge is to define which methods are best suited to reveal specific types of weakness targeted, e.g. for cases where those are known or “expected” (e.g. from service experience). In a first section, ability of dielectric measurements will be discussed. Frequency domain spectroscopy constitutes probably the more accurate dielectric measurement method; however it may not be very suitable for on-site testing because of the amount of power required for higher frequencies and of the long duration of measurements at very low frequency (VLF). Nevertheless, the method is useful for characterization of cable insulation ageing in the laboratory. Time domain spectroscopy (TDS) could also be considered. Even if the method has been shown to be less adapted to identify non-linear behaviour, TDS tends to be more suitable for on-site tests, since it does not require any significant amount of power supply, while it allows obtaining dielectric loss values at VLF within a reasonable time frame. Ability of alternative time domain dielectric measurement methods will also be discussed (e.g. voltage recovery, current discharge). Actually VLF tan delta measurements are the most popular ones and they are mainly used to identify non-linear behaviour versus voltage and typically water penetration related problems. The second measurement category could be defined by "transient" measurement based on detection of pulse propagation along the cable. The most popular one is partial discharge (PD) measurement. Relevance of signal treatment and operator interface for PD results pertinence will be underlined and the effect of the type of source used will be reviewed. Typically systems offering the most important control of measurement parameters and the best accuracy need skills and amount of time which is not often available for on-site measurements. So system providers are proposing various degrees of automation of knowledge rules and we will see that if automation could be time saving, impact on accuracy must be carefully considered. In this range of technique, impedance change analyses with TDR are also considered. Thus for the panel of topic addressed, main possible uses will be addressed and examples from each laboratory will be described. Perspectives for use of new methods will then be discussed in terms of their potential ability to focus specifics weaknesses and to better manage on-site campaign efficiency. The need of previous accurate laboratory characterization to establish evaluation criteria will also be discussed and underlined. Key words Diagnostic, Medium voltage cables, Dielectric measurement, Tan delta, Partial Discharge, Off-line JICABLE15_0215.docx Copper-clad aluminum as an alternative to copper flexible conductors for electric power cables: opportunities and challenges Alberto BAREGGI (1), Flavio CASIRAGHI (1), Luca DE RAI (1), Davide MARTELLI (1), Alessandro MAZZUCATO (2), Franco PERUZZOTTI (3), Antonio PEZZONI (3), Pietro ANELLI (4), Dustin FOX (5), Syarif YANCE (5) 1 - Prysmian SPA, Milan, ITALY. alberto.bareggi@prysmiangroup.com, flavio.casiraghi@prysmiangroup.com, luca.derai@prysmiangroup.com, davide.martelli@prysmiangroup.com, 2 - Prysmian Cavi e Sistemi Italia SRL, Milan, ITALY. alessandro.mazzucato@prysmiangroup.com 3 - Dynext SRL, Legnano (Milan), ITALY. franco.peruzzotti@dynext.eu, antonio.pezzoni@dynext.eu 4 - G.B. Studio, Milan, ITALY. anellibonvini@tin.it 5 - Copperweld, Nashville, Tennessee, USA. dfox@copperweld.com, YSyarif@fushicopperweld.com The pressure of high copper prices during the last decade requires innovative solutions to reduce its strong impact on material costs for wire and cable (W&C). Aluminum is a well-known material for producing conductors with a good ratio cost/performance ratio (conductive and lightweight) that has been used for many years. Nowadays, copper is still largely used in W&C and its replacement with aluminum presents challenges for various reasons: a larger diameter of aluminum is required to match the resistance of a copper conductor, aluminum’s mechanical properties (tensile strength) are inferior to those of copper, aluminum presents processing difficulty in fine wires (i.e. drawing to <0.5mm diameter), and aluminum offers poor corrosion resistance. Bimetallic conductors like copper-clad aluminum (CCA) offer interesting key features for niches of cables where aluminum is not a viable choice versus copper. Several grades of bimetallic conductors are available on the market, but not all of them are adequate for applications in the electric cable industry. In this sense, the manufacturing technology can seriously affect quality: cladding is strongly preferable to electroplating. The objective of this work is to evaluate metals like aluminum, CCA and tinned CCA as alternatives to copper for flexible conductors in building wires and LV power cables. Cables have been designed with conductors having the same DC resistance. Prototype cables were manufactured and characterized according to the specifications required for copper cables used in the application. Additional tests were carried out to simulate aggressive environmental conditions with heating thermal cycles. Special focus is given to the definition of high-quality CCA and its related characteristics. Special tests are described in order to select material with resistance to corrosion similar to that of copper. High-quality CCA conductors, as produced according to Copperweld technology (Copperlite™ CCA) in combination with the use of selected raw materials, show process characteristics close to those of copper, especially when it is drawn to fine diameters (i.e. multi-wire 8x0.25 mm) as required for flexible cables. The strong metallurgical bond between the aluminum and copper obtained with Copperlite™ CCA enables the drawing of fine wires (i.e. down to 0.20 mm diameter at 20 m/sec production speed, in conventional copper drawing equipment) with no impact on the Al/Cu volume ratio and maintains a strong bond at the interface between the two metals Prototype cables manufactured with high-quality CCA conductors showed performance comparable to that of copper, even in severe high-humidity conditions, whereas aluminum conductor cables failed. JICABLE15_0216.doc Electrical Performance Improvement of Polyethylene Cables using Inorganic Filler. Cross-linked Sherif ESSAWI (1), Loai NASRAT (2), Jeanette ASSAD (3), Mahmoud MOSTAFA (4) 1 : Electrical Power Dept. ,Petrojet , Cairo, Egypt,eng.sherifessawi@gmail.com 2 : Electrical Power and Machines Eng. Dept, Aswan University, Aswan, Egypt, loaisaad@yahoo.com 3 : Polymers and Pigments Dept., National Research Center, Cairo,Egypt, na_jeannette@hotmail.com 4 : Electrical Power and Machines Eng. Dept, Ain Shams University, Cairo, Egypt, eng_m.mostafa84@hotmail.com Today, in all countries in the world that utilize electricity as an efficient source of light and energy, some form of transmission and distribution system exists. Both systems carry electric current, at different voltages and they are connected to each other use underground cables. Since 1970, the cross-linked Polyethylene (XLPE) insulated power cables have been used worldwide. This insulation possesses very good electrical, mechanical and thermal characteristics in medium and high voltage networks. Due to various advantages, the XLPE insulated cables had vastly displaced the traditional classic paper insulated cables. Many studies and researches have been carried out to improve XLPE characteristics such as dielectric strength. The dielectric strength of an insulating material is the maximum electric field strength that can withstand without experiencing failure of its insulating properties. Therefore, the presenting work has been devoted to study the electrical, thermal properties of XLPE after adding inorganic filler in different percentages and tested under various conditions. Blends of XLPE with different inorganic filler such as Calcium Carbonate (CaCO3) were prepared with 20%, 30% and 50% weight percentages. The dielectric strength of blends samples were tested in several temperatures and thermal conditions: Different temperatures range (0 ⁰C, 30 ⁰C, and 100⁰C). Blends thermally stressed for 24 hrs aging in high temperatures (120⁰C, 160⁰C, and 200⁰C). The average result of 3 samples of each test were taken to minimize the error, each sample was tested 3 times to insure the results. Samples were in form of disc diameter 5 cm and 1 mm for dielectric strength test. Thermogravimetric analysis (TGA) test was also performed up to 750⁰C to determine the thermal stability of the blends. The results showed that adding inorganic filler to XLPE cables improved their electric and thermal properties. Key words XLPE cables; inorganic filler; dielectric strength; TGA; electrical and thermal properties. JICABLE15_0217.docx Challenge of fault location on long submarine power cables Manfred BAWART (1), Massimo MARZINOTTO (2), Giovanni MAZZANTI (3). 1 - BAUR Prüf und Messtechnik, Sulz, Austria, m.bawart@baur.at 2 - Terna Italia, Rome, Italy, massimo.marzinotto@terna.it 3 - University of Bologna, Bologna, Italy, giovanni.mazzanti@unibo.it Submarine power cables are designed to withstand extreme harsh environmental conditions in order to grant long endurance performances and reliability to the whole cable systems. Submarine power cables are subjected to strong mechanical stresses during the laying operations and critical service conditions in their working ambient. Submarine cables are randomly exposed in all water depth to destructive mechanical stresses caused by fishing activity, boats anchors, off shore wind park jack up rigs and natural hazards like land slides, earth quakes and others. Based on surveys about submarine cable failure data recorded worldwide over long periods, it can be concluded that the probability of experiencing at least one fault during lifetime is close to certainty for long submarine links. Statistically most damages to submarine cables are caused by human activities, only a low percentage is caused by natural hazards. Based on growing energy demand and dependency on offshore produced renewable energy, submarine power cables become essential for reliable electric power supply and often can be classified as critical infrastructure. Repair of damaged submarine power cables requires specialized ships as well as experts to recover the cable from the sea bed and replace the faulty cable section. Another critical aspect associated with long submarine cables is that, whenever a fault occurs, a fairly long time is spent for repair. For this reason, fast and efficient fault detection is essential in order to reduce the overall outage time as much as possible. The best practice commonly employed for classifying submarine power cable fault types are included in the paper, together with unique measurement results carried out in the field. 1. The paper points out that fault location on submarine power cables differs by much from classical cable fault location on buried land cables as to both conditions and measuring methods, thereby illustrating the most efficient cable fault location methods. Field results on submarine power cable faults are provided, measured on AC submarine cables as well as on HVDC submarine links. 2. A unique case study of fault location on longest HVDC Submarine Link will illustrate TDR based measurements on cable length above 400 km. The paper further focus on TDR diagram analysis in order to explain how to identify cable joints. 3. The results prove that the overall outage time for repair activities can drop significantly if the fault location system is particularly designed for detecting faults in very long submarine cables with a good measuring accuracy. 4. The hazards for operators and instruments connected to the huge amount of electrical energy that may be stored in very long links are also tackled in the paper, thereby addressing the particular safety issues involved by extra-long submarine cables. JICABLE E15_0217.do ocx Fig. 1: TDR Trace of a lo ong HVDC su ubmarine cable: SA.CO.II, Italy to Corrsica, 105 km m JICABLE15_0218.doc DGA (Dissolved Gas Analysis) diagnostic method reveals internal carbonization in oil-filled high voltage extruded cable terminations Nirmal SINGH (1), Sandeep SINGH (1), Rommy Reyes (1), Jeff HLAVAC (2), Robert SCHMIDT (2), Milan UZELAC (3), Tiebin ZHAO (4), David KUMMER (4) 1 - DTE Energy, Detroit, US, singhn@dteenergy.com, singhsk@dteenergy.com, reyesr@dteenergy.com 2 - Lincoln Electric System, Lincoln, US, jhlavac@les.com, rchmidt@les.com, 3 - G&W Electric Company, Bolingbrook, US, muzelac@gwelec.com 4 - EPRI, Charlotte, US, tzhao@epri.com, dkummer@epri.com The widespread use of extruded cable systems in the range of 138 to 500kV throughout the world has placed increasing focus on effective and economic diagnostic methods for such cables and accessories. DGA is potentially one such emerging diagnostic method for oil- filled extruded terminations. This paper covers the successful application of DGA, as validated by the relationship of dissolved gases in the termination oil, particularly acetylene to the tracking/carbonization pattern observed at the transition between the cable insulation and cable insulation semi-conductive screen of a 38 years old 138kV termination. The pattern was evidenced by the presence of carbon by means of SCM instrumentation. This was attributed to the poor preparation of the transition at the end of the cable insulation semi-conducting screen that lacked the degree of smoothness and proper chamfering essential at high voltage levels. Steep chamfer creates gap between cable insulation and stress cone. The incursion of any gases e.g., from the crosslinking process or otherwise into the gap can understandably lead to PD activity that can eventually result in a failure. It should be noted that fairly high concentrations of methane were observed in some terminations, but the isobutylene was consistently high at all terminations, both resulting from the peroxide crosslinking process. Of the 12 terminations involved in the present investigations, only one showed significant concentrations of acetylene, including other hydrocarbon gases associated with acetylene. Recognizing that acetylene is related to tracking/carbonization of oil from which it emanates, this termination was dissected, including one of the 11 terminations that did not show any acetylene at all to make comparison. The latter was found to be absolutely clean and devoid of any carbonization evidence. Unlike HPFF oil-paper terminations, extruded cable terminations with considerably reduced radial and axial fields should not show any or minimal, if any, acetylene. This is also supported by laboratory load-cycling test performed on essentially the same 138kV termination design, 12 hour 1000C heating and 12 hour 1000C cooling and 1.7 rated voltage. The results of this investigation demonstrate that the DGA diagnostic method, which has achieved great success in transformers and HPFF (high pressure fluid-filled) cable systems, particularly HPFF terminations, holds great potential for oil-filled extruded cable terminations. Based on the present investigations coupled with previous work by the upper range of acetylene and other related gases are proposed. JICABLE15_0219.docx Effect of static mechanical strain on the DC conductivity of extruded cross-linked polyethylene cable insulation Øystein HESTAD (1), Henrik ENOKSEN (1), Sverre HVIDSTEN (1) 1 - SINTEF Energy Research, Trondheim, Norway, oystein.hestad@sintef.no, henrik.enoksen@sintef.no, sverre.hvidsten@sintef.no Connection of offshore windmills to the grid requires high voltage cables capable to withstand tough environmental and mechanical conditions during service. In particular the dynamic mechanical strain subjected to the cables might accelerate the degradation of the cable insulation. While the main concern is on the mechanical strength of the metallic components, the long-term effect of the mechanical strain on the DC conductivity of the insulation is not known. This is an important parameter when assessing the long-term electrical performance of the cable insulation, especially for HVDC systems. This article presents DC current measurements performed on a medium voltage cable (95 mm2 cu conductor, 3.4 mm insulation), where the outer semiconductor was sectioned into two regions by removing two 2x mm wide longitudinal sections of the outer semiconductor. Thus the average conductivity of the insulation material for the two parts of the cable could be measured and compared. To assess the effect of mechanical strain on the conductivity of the insulation of the cable, it was wrapped around a tube with an outer diameter of 110 mm. The cable was wound around the tube carefully ensuring that one section was always compressed (smallest radius), while the other section was always under tension (largest radius). In this way the effect of tension and compression on the conductivity of the insulation could be directly compared. The current through the insulation of the two halves of the cables were then measured at voltages from 8.5 to 65kV corresponding to average fields in the insulation between 2.5 and 19kV/mm. To compare the effect of the static mechanical strain on the measured current the measurements were performed three times. First a reference measurement was performed (before subjecting the cable to mechanical strain), then one measurement immediately after winding the cable around the tube, and finally one measurement was performed after 12 months at room temperature under mechanical strain. All measurements were performed on the same cable at 40°C. Initial results show no clear effect of the static mechanical strain on the conductivity of the material. The technique developed to measure on longitudinal sections of the cable works well, allowing us to measure on two, three or four longitudinal sections of the cable. In the future similar measurements may be performed on cables subjected to dynamical mechanical strain. JICABLE15_0220.docx Improvement of Ampacity Ratings of Medium Voltage Cables in Protection Pipes by Comprehensive Consideration and Selective Improvement of the Heat Transfer Mechanisms within the Pipe Constantin BALZER (1), Christoph DREFKE (2), Johannes STEGNER (2), Volker HINRICHSEN (1), Ingo SASS (2), Klaus HENTSCHEL (3) 1 - TU Darmstadt, High Voltage Laboratories, Darmstadt, Germany, balzer@hst.tu-darmstadt.de, hinrichsen@hst.tu-darmstadt.de 2 - TU Darmstadt, Geothermal Science and Technology, Darmstadt, Germany, drefke@geo.tu-darmstadt.de, stegner@geo.tu-darmstadt.de, sass@geo.tu-darmstadt.de 3 - Bayernwerk / e-on, Regensburg, klaus.hentschel@bayernwerk.de Within rural areas or sensible road-crossings, medium voltage cables are often laid in air-filled protection pipes in order to prevent physical damage. This introduces higher thermal resistances and possibly results in (local) hotspots which may limit the ampacity rating of the whole cable system. However, calculation of the thermal resistance between the external covering and the pipe is anything but simple, because it encompasses all three heat transfer mechanisms: conduction (at the points where the cable touches the pipe), convection of the enclosed air and radiation between the outside covering of the cable and the inside surface of the pipe. The well-established formulae by Neher and Bull provide a useful approximation of these three mechanisms and are integrated in the relevant IEC Standard. Nonetheless, distribution system operators particularly in Southern Germany are now facing increasingly changing loads due to the high penetration of photovoltaic generation, leading to lower load factors but higher load peak values. Under these circumstances of a changed dynamics of the load cycle, a re-evaluation of the ampacity rating with a more precise modelling of the transient heat transfer mechanisms inside the pipes is legit. Therefore, a model of the heat transfer mechanisms of a medium voltage cable in trefoil formation inside a gas-filled protection pipe will be presented in the paper. With the help of the finite element study, using the software COMSOL, the transient heating of the cable will be studied. Then, the results of the simulation will be compared with data collected at the test field of TU Darmstadt, where cables are buried under realistic conditions and loaded with typical load cycles, derived from real data of a medium voltage grid. Temperatures at the conductor and the outside covering of one cable as well as the temperature distribution on the outside of the pipe and between pipe and soil surface are being recorded. Finally, the achievable improvement of ampacity rating by filling the pipe with thermally optimized materials compared to the air-filled pipe system, as they are installed in the field test, will equally be presented and discussed. JICABLE15_0221.docx Cable constraints due to background harmonic amplifications Yannick FILLION (1), Simon DESCHANVRES (1), Nathalie BOUDINET (1) 1 - RTE, Paris, France, yannick.fillion@rte-france.com, simon.deschanvres@rte-france.com, nathalie.boudinet@rte-france.com The use of long EHVAC cables is today a tendency of grid development, expected to be even stronger in the years to come, for connecting new clients in a short delay as well as for grid developments. When inserting long EHVAC cables in its grid, RTE is used to study reactive energy compensation for voltage stability issues taking into account zero-miss effect. Transient overvoltages are also phenomena watched during studies because of resonance. Indeed, EHVAC insulated cables are capacitive elements and as RTE’s grid is rather inductive, their association creates series or parallel resonances depending where they are seen from. These resonances are today also investigated by RTE for harmonic distortions assessment. RTE has observed in its recent studies these phenomena are responsible for background harmonic amplifications when harmonics match a resonance in terms of frequency. Amplifications increase with the length of cables to be installed reaching several tens of times the initial harmonic amplitude mostly on the first odd harmonics. This issue is especially expected with the use of cables to connect the future first French offshore wind farms. For offshore wind farm connection projects, RTE observed that harmonic voltages applied on the connection cables can be up to 20 times the harmonic voltages prior to the wind farm connections for harmonics #3 to #7 taken into account various grid scenarios including grid contingencies, load variations, and wind farm projects uncertainties. The issue was observed stronger offshore than onshore. The method used by RTE for investigating background harmonics is composed of field measurements and simulations with the EMTP-RV simulation tool. Measured harmonics are concentrated on the 3rd, the 5th, and the 7th rank on the 225kV grid with amplitudes lower than 2%. However, with amplifications up to 20, even a reasonable content of background harmonics could be sufficiently amplified. Studies presented in this paper showed that the 5th and the 7th harmonics can easily exceed the grid code limits up to 600% in the case of offshore wind farm connections for instance. This significant excess of grid code limits can be the source of power quality disturbances and could stress HV equipment including cables. JICABLE E15_0222.do ocx 138kV V Cable Systtem Qu ualification to IEC 6 60840-20 011 / EIC CS ICEA A S-108-7 720-2012 / AE S-9-06 / IEEE E 48-20 009 / IEEE 404-201 12 Ravi GA ANATRA (1), Joshua PER RKEL (2), M ilan UZELEC C (3), Jose ZAMUDIO Z (4)) 1 CME W Wire and Cab ble, Suwanee, USA rgan natra@cmew wire.com 2 NEETR RAC, Atlanta a, USA joshu ua.perkel@ne eetrac.gatec ch.edu 3 G&W E Electric, Chiccago, USA muzelac@gw m welec.com 4 Viakab ble, Monterre ey, Mexico JZ Zamudio@viiakable.com on of confo ormance req quirements ffrom multiple standards s remains aakin to a high h wire Integratio performa ance. Users express a prreference forr the cable sy ystem route via IEC / AE IC, whilst rec cognizing a value in the com mponent approach (ICEA A, for cable, and IEEE, for accessoories). This presents manufaccturers with a considera able challeng ge. Consequ uently a route to qualifyy two cable designs, outdoor terminationss, oil filled an nd dry type GIS termina ations, straight joints andd cross-bond ded joints was devveloped by G&W and Viak kable. The te est program was conductted at NEETR RAC. The paper will discusss: d design of the t test loo op including g the optim mal sselection of the t compone ents (Fig 1), ssequencing of o construction and the re equired tests s, sselection of the most strringent elem ents (voltage es, number of cycles, te n emperaturess) within the t rrespective sttandards, o outcome of the t program and cconsiderations for technical committe ees engaged d in tthe develo opment and d maintena ance of the t a aforemention ned specifica ations. Fig.1 Optimized O teest loop configuration An impo ortant factor in the design n of the test lloop for the manufacture ers was the im mpact of the e currents (Fig 2 to 4) required to satisfy the e requiremen nts of the rele evant standa ards. Fig 2 IEC on nly Fig 3 IEEE only y Fig 4 IEC & IEEE simultaneously The cable system ap pproach of th he latest itera ations of the AEIC & IEC C standards aas favored by b Utilities p and critical limittations of IEE EE 48 and IEEE 404 reqquirements that t have is reinforrced. Also, practical been exxtended from m the experie ence with Me edium Voltag ge accessorries are idenntified and discussed. These su upport curren nt efforts und derway to revview the stru ucture of thes se specificatiions. JICABLE15_0223.docx Reliability of Cable Based Transmission Grids Operated Based on Temperature Limits Rasmus OLSEN (1), Joachim HOLBOELL (2), Unnur Stella GUDMUNDSDOTTIR (3) 1 - Energinet.dk, Fredericia, Denmark, rao@energinet.dk 2 - Technical University of Denmark, Kgs. Lyngby, Denmark, jh@elektro.dtu.dk 3 - Dong Energy, Fredericia, Denmark, unngu@dongenergy.dk The Danish transmission system operator (TSO), Energinet.dk, is investigating the options for controlling the transmission grid, based on utilisation of the components temperature limitations instead of the presently used steady state ampacity limitations. The aim is, of course, to get a better cost optimisation in connection with purchasing of components but, equally important, it is also the aim to increase the flexibility within transmission grid control. However, since the raison d’être of TSOs is a high security of power supply, it is important for Energinet.dk that the transmission system reliability, as a minimum, will not be reduced during the transition from steady state current based operation to dynamic temperature based operation. In addition, the reliability investigations described in the present paper should be seen in the light of the Danish transmission cable policy. The Danish parliament has decided to underground most of the Danish transmission system within the coming 25 years, which makes focus on transmission system reliability with high shares of underground cables highly relevant. Much research within reliability of transmission grids is concerned solely with radial power systems, parallel power systems and power systems where a redundant component can be connected in case of failures. For modern transmission systems, where meshed structures rule, such analyses are of limited use and more comprehensive methods must be utilised. In the present paper are described investigations on how a Monte-Carlo approach, based on Markov processes, can be used to calculate the reliability of a power system, where the majority of the transmission lines are underground power cables. It is shown that the reliability of a cable based transmission grid can be greatly enhanced by utilising real time temperature calculations in the daily operation of transmission grids, as compared to the normally used steady state IEC ampacities. These analyses should stimulate global considerations in the direction that controlling transmission grids based on the real time thermal state of the system, instead of static current ratings, can lead not only to economic benefits, but also to an increased security of supply. The theoretical considerations are collected in a simple method for evaluating the reliability of cable based transmission grids. The method is proven to be implementable with the load flow software DigSilent PowerFactory, commonly used all over the world by TSOs, universities and research institutions. The evaluation of the transmission system reliability is thus proven to be straight forward for all power grids, which are already modelled in this or similar software. The theoretical method is tested against a modified version of the standard IEEE 14-bus test system and a significant increase in system reliability is proven, when utilising the real time thermal approach to controlling cable based transmission system as compared to steady state ampacity control. JICABLE15_0224.docx Electrothermal Coordination in Cable Based Transmission Grids Operated under Market Based Conditions Rasmus OLSEN (1), Joachim HOLBOELL (2), Unnur Stella GUDMUNDSDOTTIR (3), Carsten RASMUSSEN (1) 1 - Energinet.dk, Fredericia, Denmark, rao@energinet.dk , cra@energinet.dk 2 - Technical University of Denmark, Kgs. Lyngby, Denmark, jh@elektro.dtu.dk 3 - Dong Energy, Fredericia, Denmark, unngu@dongenergy.dk Based on the decision of undergrounding the entire transmission system up to and including 150kV plus large parts of the 400kV system, the Danish transmission system operator (TSO) Energinet.dk initiated a research project with the purpose of finding the most optimal approach to dimensioning the future individual cable lines. Also included was the goal to identify the most optimal way of operating a transmission grid consisting mainly of high voltage cables. This paper documents some of the findings in the research project, whereas a full report is presented in a PhD thesis. All the different stakeholders who are involved in designing, installing, operating and maintaining the cable grid were taken into account in these investigations. Having investigated the present state of the art within dynamic rating of cables and optimal power flow (OPF) in transmission grids, it was determined that none of the methods found in the literature, or the tools available on the market, were sufficient to fulfill the needs related to the Danish transmission grid. Together with the stakeholders, it was therefore determined that a novel concept should be developed to suit such a market based approach to cable grid operation. As it is the clear intention that the transmission grid should be operated based on the physical limitations of the cables under real time environmental and electrical conditions, the presently used method, where the ampacity of the cables is calculated for one (or a few) conditions only, is insufficient. Instead, the research team applied a concept denoted ElectroThermal Coordination (ETC) where the temperature of all lines in the transmission grid is monitored (by measurements and/or simulations), in real time, and can be predicted on the basis of measured and predicted load conditions. With this temperature information the grid operator can load the system harder and control it with higher precision than what is presently possible with the steady state approach to cable rating. Until now ETC has been of mainly academic interest, but this paper describes how ETC can be implemented in transmission systems as they look today, taking into account both political decisions and market based conditions such as the ones, the European transmission systems are operated under. The description of implementation strategies is supplemented by studying real power cable cases from the Danish transmission system, and it is shown that great benefits can be achieved when utilising ETC instead of the present conservative approach to transmission cable dimensioning and operation. The case studies show that both the grid planning, day ahead planning and real time operation of the power grid will be able to benefit from the introduction of ETC. JICABLE15_0225.doc Optical PD detection in high voltage cable accessories Alexander EIGNER (1), Thomas KRANZ (1), Klaus VATERRODT (2), Dr. Gerd HEIDMANN (2) 1 - Tyco Electronics Raychem GmbH, Ottobrunn, Germany, aeigner@te.com, tkranz@te.com 2 - IPH Berlin, Berlin, Germany, vaterrodt@iph.de, heidmann@iph.de High voltage cable accessories are expected to have a life time of more than 40 years without any failure. In order to achieve this requirement, the insulation system and its performance have to be regularly checked. The today’s most commonly used diagnostic method in order to perform this task is the electrical partial discharge measurement. This technique is based on the measurement of electrical signals with very small amplitude. Disadvantage of this technique is that due to the small amplitude it is very sensible against electrical noise caused by external electrical fields such as from transformers, overhead lines, etc. As a result of this, the electrical partial discharge measurement in a noisy environment does not always allow a proper interpretation of the partial discharge measurement results and consequently an understanding of the condition of high voltage equipment is not possible. A novel method in order to perform diagnosis of the insulation system is optical partial discharge detection. This method does not work with the electrical signals which are caused in case of partial discharges but rather detects the optical signals which are coming up at the same time. Based on this different physical process, external electrical noise can be neglected which leads to a much better usability in the field. This paper presents the physical background behind this detection technique as well as a possible solution of the integration into high voltage cable accessories. At this the setup of an integrated optical fiber including its embedding is explained. Furthermore several requirements and their solution are presented such as: void free integration mechanical stresses inside the system electrical tests (AC, DC and Impulse) The paper closes with showing the results of an integrated and operating system and compares the gathered results with an electrical measurement which was done simultaneously. Fig. 1: Setup for a simultaneous optical and electrical partial discharge detection of a test object. JICABLE15_0226.docx Automated Temperature Monitoring and Control System for Type and Design Testing of High Voltage XLPE Insulated Cable Systems Ivan BOEV (1), Rick BOBKO (1), Ziqin LI (1). 1 - Kinectrics Inc, Toronto, Canada, ivan.boev@kinectrics.com, rick.bobko@kinectrics.com, ziqin.li@kinectrics.com Polymeric insulated underground power cables are steadily replacing the oil and paper insulated cables to the extent that nowadays for the vast majority of the new cable system installations the only considered cable designs are the XLPE insulated cables. Some of the required electrical type or design tests as per as IEC and ANSI/ICEA involve testing of the cable system at particular conductor temperature while the system is energized at High Voltage. In order to do that, in the standards, it is suggested to arrange a “dummy” cable loop that is heated in the same manner as the test loop, but not energized at High Voltage. In such configuration it is easy to connect thermocouples directly onto the “dummy” cable loop conductor and monitor its temperature. Since the magnitude of the heating current in the “dummy” loop is exactly the same as the magnitude of the current flowing in the test loop, the conductor temperature of the test loop is assumed to be equal to the conductor temperature of the “dummy” loop. This method of temperature measuring is straight forward and used at many test facilities. However, the test loops for High Voltage cable systems of 150kV and above require larger clearances and occupy a significant footprint, which means that test setup arrangements including a test loop and a “dummy” loop could only fit in very large test halls. At our facilities we have initially eliminated the need for building an extra loop by inventing a way to transmit data under voltage using a wireless data logging transmitting system. Basically, the conductor temperature was measured by means of a smart link telemetry system which was installed on a length of the same cable as that which was under test. Thermocouples were directly attached onto the surface of the conductor of the control cable and were connected to a wireless transmitter nearby. The control cable was installed between the outdoor terminations as seen in Fig. 1 (in series with the test loop). The conductor in this length of cable carried the same current as the test loop conductor. In this paper we discuss our upgraded temperature monitoring and control system, which we developed and employed to replace the previously used wireless one. The new system is based on fibre-optic technologies for temperature monitoring under High Voltage. The advantage of such system is the fact that the fibre-optic cables are insulated and could be attached safely (directly) to the energized conductor. We designed a setup that allows us to continuously capture the temperature reading of the cable conductor, which enables us to implement control of the heating current continuously and automatically. The fibre-optic temperature monitoring and control system has been already tested, in monitoring and in control mode, on a 132 and on a 138kV cable system type tests and it performed very well. It is currently being deployed as the primary monitoring and control system on a 240kV cable system type test. The setup is shown in Figure 2. JICABLE E15_0226.do ocx Cable system m test setup showing con ntrol Fig. 1: C cable piece and te elemetry systtem installatiion point ystem test seetup showing g control Fig. 2: Cable sy cable and fiber-o optic tempera rature monito oring and contrrol system innstallation JICABLE E15_0227.do ocx Effec ctiveness of te ests affter ins stallation n on p power cable syste ems Peter VA AN DER WIE ELEN (1), Be ernd VAN MA AANEN (1), Fred F STEENNIS (1,2) 1 - DNV GL, Arnhem m, The Netherlands, peterr.vanderwiele en@dnvgl.co om, bernd.va anmaanen@d dnvgl.com 2 - Eindh hoven University of Technology, Eind dhoven, The Netherlands s, fred.ssteennis@dn nvgl.com Due to tthe increasin ng demand for power, the expansion of geogrraphical needd for powerr and the replacem ment of old circuits, the amount of new cable installations i is increasin g rapidly arround the world. Despite various testt programs in combinattion with oth her quality assurance a annd control programs, p failures can never completely c be b avoided. From failure e investigations, togetheer with statis stics and experien nces from ne etwork owne ers, it has b become clea ar that the la argest part of these failures are related tto degradatio on mechanisms that have e been initia ated due to im mperfectionss during insta allation of the acce essories. Thiss relates to failures f that h happen immediately after installationn as well as to t failures that onlyy happen after several or many (som metimes >10)) years of op peration. Thee reasons fo or this are closely rrelated to the e fact that accessories n need to be installed in th he field. Thee insulation system s is only com mpletely finisshed after the e installation n of the acce essories, as the insulatioon system co onsists of partly the e accessory parts and pa artly the cablle insulation. Standard ds describe many tests during cable e and access sory design and producttion (pre-qua alification, type testts, routine te ests, sample tests), but tthe final installation quality (most cruucial, see ab bove) can only be tested after installation with the “tessts after insttallation”. Th hese tests arre therefore a crucial element in the overa all quality co ontrol and arre also often n the formal point of trannsfer of resp ponsibility from the contractor (installer, sup pplier, manuffacturer) towards the netw work owner. To test the quality off the insulatio on system affter installatio on, the withstand tests arre the tests described d in the sttandards tha at should dettect imperfecctions introdu uced during installations (and transp portation). Various technologiess exist (50 Hz, H Series-Re esonance, VLF, V Damped d AC, Cosin us Rectangu ular, etc.) which ccan additionally be com mbined with detection of partial discharges ( PDs) and tan t delta measure ement. Experience with one o technolo ogy is broade er and more excepted thaan with the other, o but the actual effectiveness of these e techniquess is not really y known, especially of thhe newer tec chniques. These n newer techniq ques are try ying to gain m market share e, and could d be interestting from eco onomical, practicall or technology point of view, v but not without know wledge of the actual andd real effectiv veness of these techniques compared to th he others. Liiterature stud dies have co onfirmed thaat the effectiv veness of also the e more estab blished tech hniques is m mainly assum med and only shown wiith some sin ngle field measure ement examp ples here an nd there. Larrger scale la aboratory experiments arre almost ex xclusively done on cable system ms with artificial, unrealisstically severre, defects. This pap per presents this literaturre study and its results, togetherr with a plann ned project that t will inve estigate the effective eness of the various me entioned tec hniques in an indep pendent wayy. To obtain unquestionab u ble results, independ dency is obta ained by invo olving netwo ork owners, cable ma anufactures, accessory manufactures m s and DNV GL. Furtthermore, the planned in nvestigation involves a setup wiith a large amount a of ca able systemss on which artificial, but realistiic, defects will w be mad de and on which te ests will be repeated multiple timess to obtain statistica ally proven re esults. JICABLE15_0228.docx HVDC & HVAC Cable Systems delivered on long length drums José SANTANA (1); Pierre MIREBEAU, (2); Mohammed MAMMERI, Bernard DHUIC, (3); Franck Michon, Dominique ADAM, (2); Jawdat MANSOUR, (1); Roland BAIL (4); Frédéric LESUR (5) 1 - Prysmian Group, France, jose.santana@prysmiangroup.com, franck.michon@prysmiangroup.com, jawdat.mansour@prysmiangroup.com 2 - Nexans, France, pierre.mirebeau@nexans.com, dominique.da.adam@nexans.com 3 - General Cable, France, mohamed.mammeri@generalcable-fr.com, bernard.dhuicq@generalcable-fr.com 4 - SYCABEL, France, roland.bail@sycabel.com 5 - RTE, France, frederic.lesur@rte-france.com The need for connections and interconnections in the transmission network, HVAC and HVDC, has resulted in the selection of long links using underground cable systems. An optimisation of the long links has led to the delivery of cables using long length drums for the following reasons: Decrease of the number of joints and related civil work Decrease of the number of drums Decrease of the number of trucks for transportation Decrease of the CO2 footprint Increase of the flexibility for the joint-bay location Decrease the maintenance constraints Decrease of the laying operation time and mobilisation Decrease the number of jointing teams Decrease of the construction duration of the link The authors will address the different issues that are necessary to make such a global optimisation successful. Cable manufacturers and utilities have to perform a careful survey at the early stage of the project to prepare the works. During this engineering phase, the cable system components are selected, the best unit lengths of sectionalizing sections are defined. Cable manufacturers have to evaluate and design the expansion areas to match thermo-mechanical forces. In addition, cable manufacturers have made innovations on the cable system such as: Upgrading of manufacturing and testing facilities High capacity pulling eyes High side wall pressure resistant cables adapted to the long laying routes with curves and slopes Special accessories with high screen-to-earth withstand voltage Crane free and drum self-loading and unloading trailer New site motorized drum pay-off for high load capacity Improved pulling method for long length cables with high strength winch Recent examples of such links will be given. JICABLE15_0229.doc The degassing process of HV XLPE cables and its influence on selected electrical properties Pekka HUOTARI (1), Magnus BENGTSSON (2), Jan-Ove BOSTRÖM (3), Annika SMEDBERG (3) 1 - Maillefer Extrusion Oy, Vantaa, Finland, pekka.huotari@maillefer.net 2 - Nexans Norway AS, Halden, Norway, karl_magnus.bengtsson@nexans.com 3 - BOREALIS AB, Stenungsund, Sweden, jan-ove.bostrom@borealisgroup.com, annika.smedberg@borealisgroup.com During the manufacturing of peroxide initiated crosslinked polyethylene (XLPE) insulated cables peroxide decomposition products, primarily methane, acetophenone and cumylalcohol, are formed. Degassing of high voltage (HV) and extra high voltage (EHV) XLPE cables is a widely established practice in the industry. The prime reason is to reduce the content of methane due to its flammability and the related hazard. Issues related to potential internal pressure and effect on accessories has also been addressed. The other mentioned decomposition products, polar in nature, have a considerably lower diffusion rate and will remain in the cable over very long times. It is known that these decomposition products have an influence on electrical properties. As their content and distribution is influenced by the degassing process, it is valuable to understand to which extent these properties are modified. Degassing takes place in special chambers and is a capacity demanding and time consuming process. The planning of the degassing conditions has to take factors such as time, temperature, cable construction and the amount of cables into account. Therefore means of decreasing the degassing time without jeopardizing the technical features of the cables will allow for an optimisation of the overall cable manufacturing process. For this reason the use of a practical calculation model can provide valuable support. This in combination with reliable and specific methods for the analysis of methane would form a basis for cable manufacturers to combine optimised degassing conditions with maintained safe limit of methane. The diffusion of methane can be numerically modelled. Since the diffusion of methane takes place both during the actual crosslinking process in the continuous vulcanising (CV) line as well as in the subsequent degassing operation it is important to base the diffusion calculation on a combination of these two steps. Today the automation system of most CV lines includes a ‘curing calculation program’ that is used to determine the correct line speed and heating zone profile for a certain cable construction. It is an obvious choice to add a diffusion model as a part of this program for the calculation of methane. This paper presents a model for the calculation of methane in cables and the verification of this model by methane measurements in different HV and EHV cable constructions. It also presents studies on the effects of degassing on the content and distribution of the polar decomposition products and their influence on selected electrical properties. JICABLE15_0230.doc Dielectric strength of γ-radiation cross-linked, high vinylcontent polyethylene M. G. ANDERSSON (1), M. JARVID (1), A. JOHANSSON (2), S. GUBANSKI (2), M. FOREMAN (3), C. MÜLLER (1)*, M.R. ANDERSSON (1),(4)* 1 - Department of Chemical and Biological Engineering/Polymer Technology, Chalmers University of Technology, 41296, Göteborg, Sweden, mattan@chalmers.se, christian.muller@chalmers.se, 2 - Department of Materials and Manufacturing Technology/High Voltage Engineering, Chalmers University of Technology, 41296, Göteborg, Sweden, anette.johansson@chalmers.se, stanislaw.gubanski@chalmers.se 3 - Department of Chemical and Biological Engineering/Nuclear Chemistry, Chalmers University of Technology, 41296, Göteborg, Sweden, foreman@chalmers.se 4 - Ian Wark Research Institute, University of South Australia, Mawson Lakes, South Australia 5095, Australia, mats.andersson@unisa.edu.au Low density polyethylene (LDPE) has become the material of choice for the electrical insulation of high-voltage cables due to a combination of low electrical losses and high breakdown strength. Typically, LDPE is cross-linked in order to ensure dimensional stability at high temperatures and to prevent stress cracking. Peroxide cross-linking is most common but results in unwanted by-products that must be removed by degassing for an extended period of time at elevated temperature. Moreover, these volatile peroxide decomposition products pose a considerable health hazard, which requires a suitably adapted work environment. Hence, alternative cross-linking concepts for polyethylene insulation are of interest for cable manufacturers. We explore γ-radiation cross-linking of high vinyl-content low-density polyethylene (LDPE) and its potential use as a high-voltage insulation material. Of the three investigated resins containing 1, 0.5 and 0.17 vinyl groups per 1000 carbons, respectively, only the highest vinyl content material featured a sufficiently high gel content of more than 70% and hot-set elongation below 175%, when crosslinked with a γ-radiation dose of at least 68 kGy. Differential scanning calorimetry (DSC) and smallangle X-ray scattering (SAXS) reveal that neither the crystallinity nor the lamellar thickness of the highest vinyl-content LDPE are negatively affected by γ-radiation cross-linking. As a result, we find that the dielectric JICABLE15_0231.docx Installation of Cables System connections to Gas Insulated metal-enclosed Switchgear (GIS) Pierre MIREBEAU (1); Franck MICHON, Jawdat MANSOUR, José SANTANA (2), Mohamed MAMMERI, Bernard DHUICQ (3); Roland BAIL (4); Martial GUILLEMIN (5); yy, (6) 1 - Nexans, France, pierre.mirebeau@nexans.com 2 - Prysmian Group, France, franck.michon@prysmiangroup.com, jawdat.mansour@prysmiangroup.com , jose.santana@prysmiangroup.com 3 - General Cable,France, mohamed.mammeri@generalcable-fr.com, bernard.dhuicq@generalcable-fr.com 4- SYCABEL, France, roland.bail@sycabel.com 5 - RTE, France, martial.guillemin@rte-france.com 6 - GIMELEC, France, yy@gimelec.fr The GIS substations are more and more used specially in urban areas because of their reduced footprint as compared to open air substations. The connection of underground cables requires specific GIS terminations. Usually the GIS manufacturer is different from the cable system manufacturer. The international standard IEC 62271-209 defines the limits of supply and responsibility of each manufacturer. However, civil works are not addressed and many issues remain to be clarified. The purpose of this paper is to review the additional technical requirements that are needed to install and operate a connection between a cable system and a GIS. The identification and tests of the different components Pre-installation (when requested) of cable manufacturer insulator at the GIS manufacturer’s factory and subsequent tests Cable route dimensions (depending on the cable bending radius and supporting frame) Clearance around and under the metallic termination enclosure (depending on supporting structure for the metallic enclosure, and on the hole size in the intermediate floor) Supply of Surge Voltage Limiters (SVL) and related clearances (voltage related) Gas pressure and insulation level for safe connection works Instrumentation position, current transformer, protection around cable screen and SVL After installation tests Maintenance facilities The requirements will be discussed in reference to the CIGRE technical brochure B1-B3.33 and available international standards. Example of recent installation will be provided. JICABLE15_0232.doc Recent developments in cure control for crosslinkable polyethylene (XLPE) power cable insulation Timothy PERSON (1), Jeffrey COGEN (1), Yabin SUN (2) 1 - The Dow Chemical Company, Collegeville, USA, persontj@dow.com , jmcogen@dow.com 2 - Dow Chemical (China) Investment Co. Ltd., Shanghai, China, sysun@dow.com Insulated power cables typically employ crosslinkable polyethylene compounds as a means to deliver increased service temperature. The most common technologies to deliver crosslinking are i) freeradical crosslinking initiated by thermal homolysis of organic peroxides and ii) the formation of siloxane crosslinks which result from hydrolysis and condensation of silane-containing ethylene polymers. Although these technology platforms have been utilized for many decades, advances in crosslinking chemistries have enabled new levels of performance in the rate of crosslinking and the resistance to scorch (premature crosslinking during cable extrusion). When compared to crosslinking of low-density polyethylene using dicumyl peroxide, new technologies are highlighted which demonstrate up to a twofold increase in a characteristic scorch-time while preserving the ultimate cure potential. New formulation technology in radical crosslinking with low-density polyethylene has also been demonstrated to deliver crosslinking kinetics similar to that delivered by specialized ethylene polymers designed for high-cure speed. Within the silane-cure technology space, where the time for crosslinking of cables increases significantly as the insulation thickness increases, new technology enables crosslinking of thick sections in 24 - 48 hours without the need for external heat or moisture. These technology advances open up new opportunities in materials development for improved efficiencies in the cable manufacturing process. JICABLE15_0233.doc Validation of power cable material technology with reduced degassing burden Yabin SUN (1), Timothy PERSON (2) 1 - Dow Chemical (China) Investment Co. Ltd., Shanghai, China, sysun@dow.com 2 - The Dow Chemical Company, Collegeville, USA, persontj@dow.com Extruded cables with polymeric insulation are commonly crosslinked through the use of radical chemistry initiated by the thermal decomposition of organic peroxides. The byproducts of the crosslinking reaction based upon the use of dicumyl peroxide include cumyl alcohol, acetophenone, alpha-methyl styrene and methane. The “degassing process” for removal of byproducts in high voltage cable often involves the facilitation of the diffusion of byproducts out of the cable through the use of increased temperatures within degassing chambers, while distribution class cables are often allowed to degas under ambient conditions. A reduction in the amount of time necessary to achieve a sufficient level of degassing is viewed as a benefit in the cable manufacturing process. Using a simple multicomponent diffusion model an estimate can be made for the degree of degassing for various times and temperatures. The model enables parametric prediction of the impact of insulation thickness and temperature on a characteristic diffusion time to achieve a targeted degree of degassing. A protocol has also been established which enables the quantification of the byproduct level within manufactured cables. The model results are compared to the results obtained throughout degassing of a high voltage cable using typical degassing conditions. Alternate compositions have been developed with an objective to reduce the crosslinking byproducts and thereby reduced the required degassing time. Based upon the diffusion model a 50% reduction in degassing time was expected with the alternative compositions. The alternative composition was utilized for cable extrusion and the byproducts were measured and compared to that of a standard crosslinked polyethylene cable. The results are consistent with the expectation that the alternate composition can deliver a 50% reduction in degassing time, while also delivering an acceptable degree of crosslinking. High voltage cables manufactured with the alternate low-degassing crosslinking technology have successfully completed the Type Test. JICABLE E15_0234.do ocx Belgian exp perience e with real tim me temperature e syste em in comb bination n with distribute ed temperature sensing g techniques Pieter LE EEMANS, Bart MAMPAE EY, Patrick M MARTIN, Dennis CROMB BOOM, Jean--Pierre FALC CKENBACH H (1), 1 - Elia, Brussels, Be elgium, pieterr.leemans@elia.be, bart.mampaey@ @elia.be, patrick.martin@e elia.be; dennis.cromboom m@elia.be; je ean-pierre.fa lckenbach@ @elia.be In the latte 90’s, the Belgian B TSO O Elia decide d to integrate optical fibrres in the cabble systems of 150kV for temp perature mon nitoring. Up till now these e fibres were e used for ad d-hoc temperrature measurements on the cable circuits by means of o a mobile d distributed temperature sy ystem (DTS)) system. Th he goal of this tech hnique was to o locate hot spots s in the ccircuit and to o verify the ampacity calcculations mad de during the engin neering of th he circuit. There was no d direct need for f permanen nt temperatuure measurem ment due to the lo ow load of these cable sy ystems. Mea anwhile the situation s has changed annd several ca ables are already and will be highly loade ed due to de ecentralized and a renewab ble energy pproduction, especially e wind ene ergy producttion. The loa ad situation in the grid is changing rapidly from a unidirectional to a bidirectio onal networkk. At this mo oment there is a need frrom operatio ons side to uuse a perma anent real time thermal rating (RTTR) ( syste em on the 1 150kV underrground cable link of Kokksijde-Slijken ns due to the highe er and fluctuating load, in n order to co ntinuously optimize the lo oad capacityy. ption of the temperature t e monitoring g system Descrip All new HV cable circuits startin ng from 110kkV are equip pped with integrate ed optic fibre es (FO) in one phase (fig ure 1). Thes se FO are located u under the ou uter sheath of the cable. T Two different types of FO are u used: multim mode (MM) FO O and single e mode (SM)) FO. The MM fibre es are used d for tempe erature meassurements with w DTS systems, due to th he higher accuracy a an nd the lowe er spatial resolutio on. The SM fibres f are us sed for longe er ranges, where w the MM DTS S systems arre not capable to measurre the complete cable length. F For the 150kV V cable betw ween Koksijd de and Slijken ns a DTS system w was installed d on de SM FO. F Figure 1: HV caable 110kV with integrated F.O. Dynamiic Line Ratin ng The first fixed RTTR monitoring system s will b be installed in n the 33 km link 150kV K Koksijde-Slijkens (type EAXeCe eW 87/150kV V 1x2000/21 11) by the e end of 2014. This link transports hiigh loads du ue to the connection of the firrst offshore wind w farms a and increasin ng loads with future connnection of Belwind B 2 and Nortthwind. The data of the DTS D is transfferred over the t SCADA network n to thhe control ce enter. The real time e input of the e actual curre ent and amb bient tempera ature allows to calculate the maximum load in permane ent condition ns, maximum m overload capacity forr a given time, maximuum time forr a given overload d,.. With the technique of o RTTR Elia a has the op pportunity to o follow up tthe load of the t cable system in real time and a have an idea of the m maximum ins stant load and d the overloaad capabilitie es. The goa al of the pape er is to prese ent the expe rience of Elia with installlation of the RTTR syste em and to explain ffirst insights about the overload o cap pability of the e 150kV link of Koksijde--Slijkens by using an RTTR syystem. JICABLE15_0235.doc Thermal Dissipation Analysis of Underwater Towed-cable with Impulse Current Using FEM Pan PAN (1), Bingyu CAI (1), Shuhong XIE (2), Jianmin ZHANG (1), Jianlin XUE (1) 1 - Zhongtian Technology Submarine Cable Co., Ltd, Nantong, China, panp@chinaztt.com , caiby@chinaztt.com , zhangjm@chinaztt.com , xuejl@chinaztt.com 2 - Zhongtian Technology Group Co., Ltd, Nantong, China, xiesh@chinaztt.com In underwater towing system, the towed-cables connect the ship and towed vehicle, transmitting power and control signal. In this paper, a heavy armored towed-cable with multi-conductor wrapping single fiber optic component is presented. With the impulse current flowing through the cable, each conductor insulating layer would block the generated core heat and threat the safe operation of fiber optic. The rise and distribution of temperature under impulse current is calculated in commercial ANSYS software for three-dimensional transient simulation of the towed-cable, in which the multi-order helical structure fully considers the double-helix configuration of individual conductor wires within the wound strand. By relating the wires level contact stress to the overall loads determined through OrcaFlex, the corresponding contact heat transfer coefficients between the copper conductor and insulating layer are defined. The approach for the determination of towed-cable thermal dissipation considers the cable laying in the opening air and hanging in the moving seawater environment. Results denote that poor convection of air results in towed-cable temperature to be greater than in deep seawater. Based on paper results, the threshold for each conductor ampacity could be defined. JICABLE15_0236.docx Transients on DC cables connected to VSC converters Sébastien DENNETIERE (1), Hani SAAD (1), Pierre HONDAA (1), Antoine NAUD (1) 1 - RTE, Paris, France, sebastien.dennetiere@rte-france.com - 001 514 912 0420, hani.saad@rte-france.com, pierre.hondaa@rte-france.com, antoine.naud@rte-france.com Oil-impregnated insulation cables, such as mass impregnated (MI) cable and oil-filled (OF) cable, have been applied to DC power transmission. Since then, they have been the mainstream of DC power transmission cables. The oil-impregnated insulation cable technology has developed in response to demand for higher voltage and larger capacity. On the other hand, extruded insulation cables, in which such material as XLPE is extruded on the conductor, were first applied in Gotland to an 80kV DC line in 1999. The main advantages of XLPE cables compared with MI and OF cables are their cost and their environment impact. Nevertheless they are more sensitive to voltage transients and especially polarity reversal. Application of voltage source converters (VSCs) in power systems is rapidly growing due to advantages such as absence of commutation failures, ability of independently controlling the active and reactive power, and fast dynamic response. Insulated Gate Bipolar Transistor (IGBT) is the power electronic switch used in VSC applications. The VSC technology does not require the inversion of the voltage polarity when reversing the direction of power flow. This has made the use of extruded insulation cables easier for DC applications. Since then, the number of extruded insulation cables, used in combination with VSCs, has increased for HVDC power transmission applications. Even if VSC does not require the inversion of the voltage polarity, many events can generate transients on cables that are not covered by standard tests. This paper presents some examples of typical events that lead to voltage fluctuation on cables connected to VSC converters. DC faults or internal faults in converters can result in significant overvoltages at the DC cables which persist even after the system has been disconnected from the AC networks. Cables discharging and travelling waves propagation generated by faults or grounding switches operation impose stresses on cables insulation that are not well described in literature and usually not covered by cables specifications. Using the HVDC VSC test system proposed by CIGRE B4 study committee, these transients are described, compared against the standard tests for lightning and switching impulses. Technical solutions to limit stresses on cables are proposed and discussed. JICABLE15_0237.docx ICEA Standard S-97-682-97 hyperbaric Accelerated Water Treeing Test (AWTT) performed at 250 and 310 psi John T. SMITH, III (1), Daniel ISUS (2), Michael D. ALFORD (3), Masoud HAJIAGHAJANI (3), John T. WHIDDON (4) 1 - General Cable Corp, Scottsville, TX, 75688 (USA), jsmithiii@generalcable.com 2 - Grupo General Cable Sistemas, S.A. GCC Manlleu, Spain, disus@generalcable.es 3 - Chevron Energy Technology Company, Houston, TX, 77002 (USA), mikealford@chevron.com, Masoud.Haji@chevron.com 4 - Aker Solutions, Mobile, AL 36605, (USA), John.Whiddon@AkerSolutions.com The Accelerated Water Treeing Test (AWTT) of ICEA standard S-97-682-97 has been performed on tree-retardant crosslinked polyethylene (TRXLPE) insulated cables having blocked and unblocked conductor strands, at 1 (ambient), 250 and 310 bar hydrostatic water pressure for up to 450 days. Minimum residual dielectric AC breakdown strength requirements of the ICEA standard after AWTT via a step-rise high voltage time test (HVTT) at 120, 180 and 360 days were met at all three (3) test pressures, and were statistically equivalent at all test pressures. Degradation rates of AC breakdown strength were also identical at all test pressures. The number of bow-tie trees observed at or near HVTT failure sites as a result of AWTT being performed at 250 and 310 bars were higher than at ambient pressure (1 bar). The bow-tie tree density (#/.in3) growth rates at 250 and 310 bar are also greater than at 1 bar. Vented treeing (either at the conductor shield or insulation shield interfaces) at 250 and 310 bar was essentially non-existent. AWTT performed at 250 bar for 270 days, followed by an additional 180 days at 310 bar, also showed equivalency (with regard to levels and degradation rates for breakdown strength and treeing) results at 1 and 310 bar testing. These test results indicate that this TRXLPE insulation system can be expected to operate reliably at its intended operating voltage in sea water depths of up to 10,000 feet for its projected 40-year life. Key words Accelerated Water Treeing Test, AWTT, AC breakdown strength, bow-tie trees, vented trees, hyperbaric pressure, TRXLPE, degradation rates, high voltage time test, HVTT JICABLE15_0238.doc Practical research on upgrading of 10kV power cable. Biao YAN (1), Li ZHOU (1), Jie CHEN (1), Fengbo TAO (1) 1 - Jiangsu Electric Power Company Research Institute, Nanjing, China, whuvain@126.com, zl_jtt@163.com, 2008840320@163.com, hvtaofb@163.com Upgrade and uprating of underground existing system is the scope of work of some GIGRE working group, who dedicated to deal with the improvement of service life, environment impact and safety of power cables. This paper presents some work in practical research on upgrading of 10kV power cable system. Guidelines of new cable design are applied to assess the feasibility of existing power cable system upgraded to higher voltage, tests of insulation performance was carried out on many running 10kV power cables, testing results show that the majority of cables in good insulation can pass all type tests of 20kV power cable, some tests were conducted to evaluate the remaining life of these cables, actual running with load of these cable show that its can run well in higher voltage. JICABLE E15_0239.do oc The charactteristics s of rec cyclable e therm mo-plastiic base ed on polye ethylene e blends s for exttruded cables c Lunzhi L Li (1), Lisheng Zhong *(1)), Kai Zhang (1), Guangh hui Chen (1), Shuai Hou ((2), Mingli Fu u (2) 1 - State e Key Labora atory of Electtrical Insulatio on and Powe er Equipmen nt,Xi’an Jiaotoong University, demo oniacpea@sttu.xjtu.edu.cn n, lszhong@ @mail.xjtu.edu u.cn, flowerlm mzk@stu.xjtuu.edu.cn, smalllbird@stu.xjttu.edu.cn 2 - Electtric Power Re esearch Instiitute of China a Southern Grid, G Guangz zhou, housh huai@csg.cn n, fuml@csg.cn Due to tthe poor recyyclability and d high energ gy consumpttion of XLPE E, it is very aacute to develop new environm mental-friend dly insulation n materials. T The binary polyethylene e blend HDP PE+LLDPE has h been considerred as one of the poten ntial non-cro osslinked environmental--friendly insuulation materials with compara able electrica al and mecha anical perform mances. In this in nvestigation, the propertties of binarry polyethyle ene blend sy ystems whichh contain HDPE and LLDPE h have been measured m and d discussed.. The blends are blending g by torque rrheometer in n different proportio ons. Tensile and electric cal tests havve been take en on these blends with different pro oportions. From the e results, a blend b system m which has tthe most exc cellent comp prehensive peerformance has been chosen: 70%wt LLDPE-30%wt HDPE H (31 MP Pa in tensile strength, 82 29% in breakking elongation, 3.2× m in volum me resistivity y and 94kV V·mm-1 in breakdown strength oof 63.2% cu umulative 1015 Ω·m probabiliity). It is also o pretended that crystalllinity of the blends b increase and am orphous is dispersed d evenly in crystalline phase by taking diifferential sc canning calorimetry(DSC C) and mic croscopic observattion after co orroding in boiling b n-hep ptanes, there efor the blends have suuperior perfo ormance. Furtherm more, water-ttreeing test of the chossen blend sh hows that the chosen m material can suppress water-tre eeing. In summary, the recyclable thermo-plastic blends have h great ppotential in using for on of green insulation extruded d cables and can develop p new directio i ma aterials for poower cables. JICABLE E15_0240.do ocx Diagn nostics of conttrol and instrum mentatio on cable es in nu uclear powe er plantt via tim me-freq uency domain reflecttometry y with optim mal referrence siignal Chun-Kw won LEE (1),, Seung-Jin CHANG C (1), Moon-Kang JUNG (1), Yee-Jin Y HAN N (1), Geon-S Seok HIN (1) LEE (1), Jin Bae PARK (1), Yong-June Y SH 1 - Yonssei Universityy, Seoul, Rep public of Kore ea, ry537 79@yonsei.a ac.kr , crave@ @yonsei.ac.kkr , moonrive er132@gmail.com , hanyj yj90@yonsei.ac.kr , epoonseok@hanmail.com , jb bpark@yonse ei.ac.kr , yon ngjune@yons sei.ac.kr mentation (C C&I) cabless are used for sensin ng critical pparameters such as Control and instrum temperature, to monitor performa ance and to control the reactor r opera ation which aare considere ed one of the mostt crucial com mponents in nuclear n powe er plant’s saffety. Moreove er, the C&I ccables are ex xposed to severe e environmenta al aging facttors such as thermal and d radioactive e sources thaat aggravate e aging of C&I cab bles. Therefo ore, a non-d destructive d diagnostic te echnique, ca apable of asssessing the e cable’s condition n, estimating g its remaining life, and locating deffects before the failure ooccurs is req quired for safe ope eration of nucclear power plant p operati on. Among vvarieties of cable c diagnostic techniqu ues in physic cal, chemical and electriccal dimensio on, one of the electtrical diagno ostic techniqu ue, time-freq quency doma ain reflectom metry (TFDR R) is characte erized by providing g benefits of both time do omain reflecttometry (TDR R) and frequency domainn reflectomettry (FDR) and also o non-destructive which does not de estroy cable under test. Figure F 1 deppicts an experimental result off TFDR. Th he first grap ph on the ttop illustrate es the incident and thee reflected signal in oscillosccope and the e second gra aph describe e the Wigne er-Ville distrib bution of refference and reflected signals in time and frequency f do omain simulta aneously. Th he last graph h shows timee-frequency the cross correlatio on results off distribution signals. main reflectoometry Fig. 1: Cable faultt detection ussing Time-Frrequency dom One of a advantages of o the TFDR is that it allo ows one to de esign the optimal referennce signal in time and frequenccy domain simultaneously considerin ng cable length and insu ulation of cabble under te est. Since the reso olution and th he accuracy of TFDR de epend on design of parameters of thhe reference signal in time and d frequency domain; d it is important to o design the optimal para ameters of thhe reference signal to gain the e optimal perrformance of detection a and location n of defects on cable unnder test. Att present, TFDR m method to sett parameters s requires ne etwork analyz zer to determ mine the freqquency chara acteristics and both h ends of the e cable shou uld be conne ected to the network ana alyzer togethher which is not easy task to a apply to the installed cablle in the nuc lear power plant. p Therefo ore, it is neceessary to develop the JICABLE15_0240.docx algorithm which obtains optimal parameters for each cable under the trade-off relationship between the resolution and the accuracy. This paper will propose the automatic algorithm which optimizes parameters (center frequency, bandwidth and time duration) of the reference signal in time and frequency domain. The followings are steps to implement the algorithm. Find the cable length and rough center frequency region by observing the attenuation of the reflected signal at the cable end Set the minimum bandwidth for acquiring the specific resolution by changing the bandwidth Set the time duration which satisfies the uncertainty principle Determine the center frequency with selected bandwidth and time duration Detailed procedures and algorithm will be presented in full-paper, but the proposed technique does not require extra devices to find the adequate frequency bandwidth and can be used on site immediately. Furthermore, the TFDR experimental results of a cable with joint such as splice, terminal block and thermal/mechanical faults will be presented in order to verify the usefulness of the algorithm for selecting optimal parameters. We could expect the best result of TFDR and time-saving for selecting optimal parameters by using this algorithm. Key words Reflectometry, Control and Instrumentation Cable, Fault Detection, Cable Insulation JICABLE15_0241.doc Modeling and simulation of failures in high temperature superconducting cable for detection and location via timefrequency domain reflectometry Geon Seok LEE (1), Gu Young KWON (1), Seung-Jin CHANG (1), Chun-Kwon LEE (1), Yee-Jin HAN (1), Jin Bae PARK (1), Yong-June SHIN (1) 1 - Yonsei Univerisity, Seoul, Republic of Korea, seok@yonsei.ac.kr , kgy765@gmail.com , crave@yonsei.ac.kr , ry5379@yonsei.ac.kr , hanyj90@yonsei.ac.kr , jbpark@yonsei.ac.kr, yongjune@yonsei.ac.kr In the areas of high-density power consumption, such as metropolitan areas and industrial facilities, high temperature superconducting (HTS) cable, which is capable of high current density transmission, is expected to play an important role in new electric power systems. However, when installing the cable, there are number of limitations to bend, twist, and load, because of the brittleness of the HTS material. Furthermore, if the superconductivity is lost due to defects from segments of HTS cable, cryogenic failures for example, the electrical resistance will rapidly increase and the quench phenomenon will result in a change in the local temperature and vice versa. If the failures of HTSbased power system occur, they can cause serious consequences such as relatively long recovery time and power shortages due to failures of the large-scale HTS electric power cable. Unfortunately, owing to the structure of cryogenic cooling system of HTS cable, it is difficult to detect the faults of HTS cable by conventional cable diagnosis methods such as partial discharge (PD). Moreover, it is possible to measure the liquid nitrogen's temperature only at the termination of the HTS cable. Thus, it is necessary for us to develop a new non-destructive method that can detect and locate local failures of HTS cable. In this paper, we propose applications of time-frequency domain reflectometry (TFDR) for HTS cable, which allows us to design reference signal in time- and frequency- domain simultaneously considering physical characteristics of cable under test. Modeling a real-world HTS cable for simulations is carried out using the EMTP/ATP. The HTS cable under test is rated 22.9kV, 50mVA and 7 meters in length. Since the EMTP/ATP program does not provide all the physical components of HTS cable, there are number of difficulties to setup HTS cable model. Thus, we proceed with the modeling considering the following parameters; (1) the internal structure, (2) the resistance variation with temperature, and (3) self-inductance and mutual inductance of layers. Furthermore, as shown in Figure 1, we develop a cryogenic cooling system using a HTS cable, a cooling pool, and a LN2 tank. TFDR system is composed of the followings: generating the input signal part using arbitrary waveform generator (AWG), receiving the input/reflected signal part using digital storage oscilloscope (DSO), connecting part between a HTS cable and probe accessories. Fig. 1: Cryogenic cooling system and TFDR system. JICABLE15_0241.doc The analysis results include the validation of the effectiveness for TFDR. The proposed model of the HTS cable in EMTP/ATP and simulation with real-world HTS cable show the new non-destructive method can provide detection and location of local failures of HTS cable. We expect that the proposed method can improve sensitivity of diagnostics of HTS cable so that it will be applicable to real-world electric power systems, and guarantee safe operation. Furthermore, the commercialization of longdistance transmission with HTS cable will be accelerated. JICABLE15_0242.docx Maintenance Decision Models for Java-Bali 150kV Power Transmission Sub Marine Cable Using RAMS Zivion SILALAHI (1)(2), Herry NUGRAHA (1)(2), Ngapuli SINISUKA (2) 1 - PLN Indonesia, Jakarta, Indonesia, zivionsilalahi@yahoo.com , herry.nugraha@gmail.com 2 - School of Electrical Engineering and Informatics - Bandung Institute of Technology, Bandung, Indonesia, n_sinisuka@yahoo.com Since assets have a long operational life in electrical power system, it requires efficient maintenance planning to perform effectively throughout its life cycle to meet its operation goals. The application of Reliability, Availability, Maintainability and Safety (RAMS) analysis is currently developing in the field of electrical power system. The focus of this paper is to demonstrate the applicability of RAMS to analyze a maintenance planning on the operation of 150kV submarine cables in Java-Bali 150kV Sub Marine Power Transmission system in Indonesia. This system is built for interconnecting Java and Bali system through four HV transmission lines from Gilimanuk to Banyuwangi, combinated of 150kV overhead line and 4.8 km sub marine AC cable under Bali Strait. The paper will present approaches and models for estimating RAMS targets based on the service quality requirements of the power system in accordance with load forecasting demand. A model will be developed to achieve the RAMS target in maintenance strategy by choosing an effective maintenance interval and detection probability respectively. This will be illustrated by a case study on the maintenance strategy for Java-Bali 500kV Submarine Power Transmission cables. In order to determine the cost-effective solution, LCC should be used. The maintenance strategy with lowest LCC will be the cost effective maintenance strategy. Monte Carlo simulations will be used to develop models to achieve the objectives of this paper. Keywords - Maintenance Decision Models, RAMS, 150kV Power Transmission Submarine, Risk Analysis, Cost Effective Maintenance Strategy, Monte Carlo. JICABLE15_0243.docx The use of life cycle cost analysis to determine the most effective cost of installation 500 kV of Java-Sumatra power interconnection system Herry NUGRAHA (1)(2), Zivion SILALAHI (1)(2), Ngapuli SINISUKA (2) 1 - PLN Indonesia, Jakarta, Indonesia, zivionsilalahi@yahoo.com , herry.nugraha@gmail.com 2 - School of Electrical Engineering and Informatics - Bandung Institute of Technology, Bandung, Indonesia, n_sinisuka@yahoo.com In order to transfer 3,000 MW capacity of the electricity from the Mine-Mouth Coal-fired Power Plants in South Sumatra to the load center in Java, PLN Indonesia intends to build the Java-Sumatra Power Interconnection System. The scopes of these Power Interconnection System works are including: 34 km HVAC 500 kV Transmission Line in Java, 254 km HVAC 500 kV Transmission Line in Sumatra, 110 km HVDC 500 kV Transmission Line in Java, 354 km HVDC 500kV Transmission Line in Sumatra, and 40 km 500 kV HVDC single core submarine cables from Java to Sumatera. This paper will analyze the financial feasibility study to ensure if the project has economic benefit, and the asset would be used effectively and efficiently along its benefit period using Life Cycle Cost Analysis (LCCA). There are several alternatives could be done in the building process, in terms of building stage and time schedule. In this paper, a LCCA will be simulated to analyze three alternatives based on financial aspects, reliability aspects, as well as load demand characteristics. As the output of this paper, the decision will be made about which alternative is the most profitable. Cash Flow and Monte Carlo simulations for a period of 30 years operation of the Interconnection System are part of the LCC models to achieve the objectives of this paper. Keywords - Life Cycle Cost Analysis, LCCA, Java-Sumatra 500 kV Power Transmission Submarine Cables, Monte Carlo. JICABLE15_0244.doc The network connection of Niehl 3 CCPP - the first 380kV long-distance cable project in Germany since the Bewag projects in 2000 Fabian SCHELL (1), Heinz UHLENKÜKEN (2) 1 - Fichtner, Stuttgart, Germany, fabian.schell@fichtner.de 2 - Rheinische Netzgesellschaft, Cologne, Germany, heinz.uhlenkueken@rng.de Rheinenergie, the municipal utility of Cologne, is extending the existing CCPP in Niehl with a new 450 MW block. Due to the fact that the plant location is inside a harbor area, the grid connection has become a significant challenge, both - technically and legally. With a total length of almost 9 km, the approved underground section of the Niehl 3 grid connection (project name NAN3) will be the longest 380kV point-to-point XLPE underground cable link built in Germany since the Bewag tunnel projects in Berlin in the late 90ies. Besides providing the technical particulars of this new 380kV cable system, this paper illustrates the challenges that the project developers, planners and contractors faced, resulting from a cable route which almost entirely leads through densely populated and industrial areas. First and foremost, there are the numerous HDD sections for road and railway crossings as well as plenty of existing utility lines in the vicinity of the cable trench. Based on the given design criteria, Rheinenergie’s approach of establishing the most efficient solution for construction, thermal and electrical needs is explained. Furthermore, background and details are provided of the extensive quality control program undertaken throughout production, the pre-execution phase and commissioning. The test program for this project includes another innovation, as all tests were based on DIN VDE 0276-2067, the new German EHV cable standard (corresponding to IEC 62067) that came into force in summer 2013. According to that, a so-called “system sample test” covering cable samples from all production lots and a cable joint from current production had been requested besides the “normal” routine and sample tests. Moreover, for the first time in Germany the “extension of an existing prequalification” (ePQ) as set forth in section 13.3 plus the National Comment (NC.2) of the above mentioned new German standard DIN VDE 0276-2067 has been performed. The differences from IEC 62067 requirements as well as some explanations for the somewhat more stringent parameters of this prequalification test are set out in this paper. On top of the final high voltage test after installation according to DIN VDE 0276-2067, the prescribed commissioning test program foresees a heating cycle test of the fully installed cable system. The somewhat elaborate planning activities, benefits and outcomes are highlighted in this paper. With the anticipated successful completion of the commissioning test program in the second quarter of 2015, one of the most complex underground cable projects in Germany will come to an end. And Germany’s longest 380kV XLPE cable system will be handed over to its owner on schedule for commissioning of the new Niehl 3 CCPP. JICABLE15_0245.docx The 110kV cable thermal field analysis based on the thermal path model and simulation calculation Miao ZHAO (1), Qinxue YU (1*), Lisheng ZHONG (1), Shuai HOU (2), Mingli FU (2) 1 State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiao tong University zm3112162010@stu.xjtu.edu.cn, yuqinxue@mail.xjtu.edu.cn, lszhong@mail.xjtu.edu.cn 2 - Electric Power Research Institute of China Southern Grid fuml@csg.cn, houshuai@csg.cn The heat dissipation problem is important in high voltage XLPE extruded insulation cable, which restricts its carrying capacity. In this paper,the 110kV cable simulation model and the thermal path model are established according to cable size and material thermal properties of each layer. The temperature distribution of actual operating cable can be obtained through ANSYS if the cable conductor current and surface temperature is known, also it can be calculated in each layer of the cable through the thermal path model. The results of simulation model and thermal path model are analyzed and compared. Simulation model and thermal path model can be verified and updated after measuring each layer temperature of actual operating cable by thermocouple. The experimental results show that the accurate cable temperature distribution in each layer can be calculated form updated thermal path model and simulation model, which can provide suggestion for the selection of covering material and design for cable structure. JICABLE15_0246.doc Withdrawn by the author, in order to participate to the YRC Contest Space charge behaviors of PP/EPDM/ZnO nanocomposites for recyclable HVDC cable Bin DANG, Jinliang HE, Jun HU, You ZHOU 1 - State Key Lab of Power Systems, Dept. of Electr. Eng., Tsinghua Univ., Beijing, China. db13@mails.tsinghua.edu.cn, hejl@tsinghua.edu.cn, hjun@tsinghua.edu.cn, zhouyao6811@163.com Extruded HVDC cable based on polymeric materials has more advantages than old paper/oil for medium and high voltage applications. The materials adopted by extruded HVDC cable manufactures are in fact most based on the polyethylene. They are mainly cross-linked polyethylene, ethylenepropylene rubber and low-density polyethylene. Unfortunately, although XLPE and EPR have excellent thermo-mechanical properties, they cannot easily be recycled. In addition, LDPE is eco-friendly, but it has too low operating temperature to meet the ever-growing power demand. To minimize the environmental impact of extruded HVDC cable, the selection of cable materials becomes a serious concern. Polypropylene offers, potentially, a route to improved insulation systems by virtue of its higher melting point and excellent DC breakdown strength. However, traditional isotactic polypropylene is very brittle for inclusion into practical cable. By adding a rubber phase, the ductility of PP can be enhanced. Meanwhile, the space charge accumulation of direct current cable affects DC resistivity and breakdown strength due to the enhancement of the local electric field. In this paper, we investigated morphology, Fourier transform infrared, thermal, thermo-mechanical and especially space charge behaviors in PP/EPDM blend modified by 0.5-5% nano-ZnO. The nano-ZnO is surface modified by titanate coupling agent to avoid agglomeration. These properties were taken together to identify the most suitable candidate materials for future HVDC cable. It was found that PP blended with 40wt% EPDM modified by 1% ZnO enormously suppressing space charge accumulation (Figure 1) offers the most optimal properties for use in eco-friendly extruded HVDC cable insulation. Key words: Polypropylene, EPDM, ZnO, HVDC cable, recyclable, nanocomposites, morphology, Space charge. JICABLE15_0246.doc Withdrawn by the author, in order to participate to the YRC Contest 0s 60s 180s 300s 600s 30 20 40 Anode Space charge density (C/m3) Space charge density (C/m3) 40 10 0 -10 -20 -30 20 0 -10 -20 -30 Cathode Thickness (um) Thickness (um) (a) 0 phr ZnO, 20 40 Anode Space charge density (C/m3) 30 10 0 -10 -20 40 0s 60s 180s 300s 600s 20 Anode 20 0 0 -20 -20 -30 Cathode Cathode -40 -40 -40 200 0 Thickness (um) Thickness (um) (c) 1 phr ZnO (d) 3 phr ZnO 40 Space charge density (C/m3) Space charge density (C/m3) (b) 0.5 phr ZnO 0s 60s 180s 300s 600s 40 200 0 200 0 Anode 10 -40 Cathode -40 0s 60s 180s 300s 600s 30 0s 60s 180s 300s 600s 20 Anode 0 -20 Cathode -40 200 0 Thickness (um) (e) 5phr ZnO Fig. 1:Space charge distributions under a DC field of 30kV/mm. JICABLE15_0247.docx Improvements on dry type design for GIS and transformer termination up to 300kV, by means of adjustable compression force. Oldrich SEKULA (1), Dr. Guoyan SUN (1), 1 - Brugg Kabel AG, Klosterzelgstrasse 28, 5200 Brugg, Switzerland, oldrich.sekula@brugg.com, guoyan.sun@brugg.com , Experiences from identical in house technology up to 170kV at Brugg Kabel AG and existing finite element simulation allowed developing a new GIS/transformer termination for 300kV XLPE-Cable with cross section up to 2500 mm2. Such product has specific peculiarities like wide application range and optional plug-in characteristics. Developed design has a wide application range for each stress cone. Such application range allows compensating to a quite large extent the manufacturing tolerances of the cable insolation diameter. As further improvement adjustable pre-load of the compression springs further allow an extended installation temperature range of 0 ÷ 40°C, granting optimal interface contact pressure at the cablestress cone and stress cone-epoxy insulator interfaces at any operating temperature. In addition, depending on the chosen application, it is possible to either install the plug-in or the locked-in dry-type termination. Development activity has been finalized with type tests at three different voltage levels: 170, 245 and 300kV and having been documented and certified by an independent third party authority. JICABLE15_0248.doc Gravitational cooling of cable installations Heinrich BRAKELMANN (1), Volker WASCHK (2) 1 - BCC Cable Consulting, Rheinberg, Germany, heinrich.brakelmann@uni-due.de 2 - nkt cables, Cologne, Germany, volker.waschk@nktcables.com New possibilities are shown to eliminate hot-spot-regions in cable routes by means of a sectionalized gravitational water cooling. This type of cooling is characterized by low complexity as well as autarkical and reliable low-maintenance operation, without active elements like pumps, coolers etc. Principle and effectiveness are demonstrated for a powertubes-cable installation, comp. fig. 1. Two heat absorbing pipes, which are closely neighboured to the cables, are connected with two heat dissipating pipes which are installed parallel, as near as possible to the soil surface. The two lower and the two upper pipes are connected with each other by means of vertical pipes at both ends of the cooling section, thus building two closed cooling circuits, filled with water. As it is shown, with growing warm cables and pipes a water circulation will set in with only some cm/s but with surprisingly good cooling effects. In principle,, a sensible part of the cables losses are extracted by the cooling pipes and dislocated and dissipated into a more favorable region of the cable trench. Especially impressive is the effectiveness even for very long cooling sections up to e.g. 1000 m. The shown examples elucidate, that even severe thermal impacts by steam pipes, other cables etc. can be controlled by means of such arrangements. JICABLE15_0248.doc Fig. 1: Thermal bottleneck over 50 m with steam pipe in a depth of 2.0 m and a cable double-system heat dissipating pipes 380-kV-VPE-cables 2500 mm2 RMS; I = 3467 A; m = 0,80 cable double-system in a duct with great laying depth heat absorbing pipes below: cooling facilities (schematic) expansion reservoir cable h cooling pipes JICABLE15_0249.doc Influence of the corona effect on overpressures in the lines and the electrics stations of nominal voltage of 330kV Nahid MUFIDZADA (1), Hocine KADI (1), Salma CHERIF (1) 1 - Mouloud MAMMERI University, Tizi-Ouzou, Algeria, mufidzada@yahoo.fr, kadihocine1@hotmail.fr, samo_cher86@yahoo.fr We consider the influence of the corona effect on overpressures in the lines and the electrics stations. In order to evaluate this influence, a model reproducing the corona effect was developed. It is found that the model with five branches is sufficient to study the influence of the corona effect on the transitory processes created by the propagation of the waves of impulse overpressures in the lines. As model, we use model proposed by the polythechnique university of Saint-Petersbourg, with adding a branches that characterizes the remoteness of the driver’s loads at thje time of stop of the corona effect and fifth parallel branches to widen the convergence of the features of the line with the one of the studied model. Corresponding calculations are made for a diagram line-transformer of nominal voltage of 330kV. The obtained results show that the corona effect considerably influences the deformation of the waves of overpressures and consequently, on overpressures in the transformers. The influence on the amplitude of overpressure is approximately 6%. The reduction in overpressure under the influence of the increases in the capacity and the conductance of the line is stronger than the increase of the overpressure because of the reduction in the characteristic impedance of the line. JICABLE15_0250.docx Assessment of environmental impact of submarine cables and offshore connections Damien SAFFROY, Frédéric LESUR, Aurore RAOUX 1 - RTE, Paris, France, damien.saffroy@rte-france.com, frederic.lesur@rte-france.com One significant measure for the development of renewable energies in France was the launching of call for tenders by the energy regulation commission. Six wind farms (500 MW each) along the French coast are to be connected between 2018 and 2023. RTE is responsible for the building, operation and maintenance of the HVAC export cables. Further projects of submarine HVAC and HVDC links are planned by RTE within the next decade, especially a new interconnection with England (2020) or a national connection along the Mediterranean coast by the sea (2021). Whereas taking biodiversity into account is already a regulatory requirement and a strong commitment by RTE for land cable links, the French transmission system operator wants to maintain this commitment at a high level for submarine connections. Several studies have been performed to improve the knowledge of marine coastal biodiversity, in order to assess the potential impact of cable systems, to measure their actual long-term impact, to protect biodiversity at each stage of a project, and to enhance biodiversity more generally. Three specific areas of major stake have been considered to measure the potential impact and evolution over time: the landfall on the cable route, the transformer platform or submarine substation (HVDC cable), and artificial reefs. Several R&D projects have been initiated to explore these fields of study, following the opportunity of the connection of the first offshore wind farms. Guidelines have been written by the national department in charge of consultation and environmental topics, then addressed to the project teams, including: The different stages of the cable system life cycle (installation, operation, dismantling), The analysis of the initial conditions (physical and natural environment, human activity, cultural heritage and tourism), The evaluation of the potential impact (temporary or permanent) of the project, Mitigation and/or compensation measures to avoid, minimise or compensate the expected impacts. Specific and didactic cards have been circulated in order to improve the dissemination of these new skills. A guide helps the project teams along a structured process for the whole study, finalised by the environmental impact study report. The authors discuss in the submitted paper the approach to build the technical and environmental reference source, and share their feedback within the utility. JICABLE15_0251.docx Electro-Thermal Analysis of Low and Medium Voltage Cable Joints Prof. Ossama GOUDA (1), Dr. Adel ZEAIN (2), Dr. Adel ELFARASKORY (3) 1 - Cairo University 2 - Aswan University 3 - High Voltage Research Centre Because of manufacturing, shipping and installation limitations of all power cables, their lengths are produced and laid in a number of separate lengths which are joined together on site and terminated at required positions. Also, to clear the faults of underground cables one or more of joints are required. These joints and terminations are considered to be the weakest parts of the cable system. Because of handling insulation of cable joints, the thickness of insulation layers is thicker. For this reason the cable joints represent hot spots in the cable system. In this paper, a suggested method to investigate the joint temperature distribution of low and medium voltage cables is presented. The effect of the dimensions of the connector on the temperature of the cable joint, which normally produces a dip in the temperature at the center of the cable joint, is investigated. This dip in the temperature increases with increasing the length and the thickness of the connector. The suggested method, which is presented in this paper, is a general analytical method for calculating the temperature distribution in a cable joint and the cable adjacent parts. This method takes into consideration the longitudinal heat flow as well as the variation of the conductor losses with temperature. This method has been applied to a joint of 11kV, 3150 mm2 which is widely used in the distribution network of Egypt and the results of this method are compared with those obtained by the finite element method. The thermal field in the medium of the cable is governed by the following differential equation: 1 T 1 T q x th x y th y Where T denotes the temperature at any point (x,y) in the plane around the underground cable, th represents the thermal resistivity, and q is the heat generation rate. Fig. 1 shows the comparison between the calculated temperatures along the conductor uf the cable joint calculated by analytical method and finite-element method. Temperture (Degrees Celsius) 88 FEM Analytical Method 86 84 82 80 78 76 74 72 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Distance from the center of the joint (m) Fig. 1 Comparison between the calculated temperatures along the joint part and other two parts using the analytical and finite-element methods It is seen that the temperatures calculated by the analytical method is in a good agreement with those obtained by finite-element method. Fig. 2 gives the temperature distribution for half of the joint and the adjacent cable part starting from the end of the joint. The other half of the joint is similar to the first JICABLE15_0251.docx one. In this figure the thickness of connector is fixed at constant value (2t=4 mm), while the half of the connector length (X) is changed to take the values X = 0.0625 m, 0.125 m, 0.25 m and 0.45 m respectively, the calculations are carried out at full load cable current and 22 oC constant ambient temperature, the cable laying depth is 0.8 m and the thermal soil resistivity is 1.2oC.m/w. Similar results are given while the thickness of the connector takes the following values: 2t =8 mm, 12 mm and 20 mm. As it is given it is noticed that the effective parameter in reducing the joint temperature is the connector length. Increasing the connector length reduces the joint temperature even with thin connector, as noticed in Fig 2 90 2t=4mm 2t=4mm 2t=4mm 2t=4mm Temperture (Degrees Celsius) 88 86 84 & X= 0.0625 m & X= 0.125 m & X= 0.25 m & X= 0.45 m 82 80 78 76 74 72 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Distance from the center of the joint (m) Fig. 2 Conductor temperature profiles at fixed connector thickness (2t=4 mm) and various lengths of connector In this paper the conductor temperature profile along the cable joint and other adjacent parts is calculated by two methods, namely: suggested analytical method and finite-element method. As well as, the distribution of the temperature within and around the three-core cable is calculated using the finite-element method. Also, an experimental study was carried out to measure the temperature at some points alone the joint and adjacent cable parts, at various cable loading currents. From the study carried out in this paper, it is concluded that: The temperatures calculated by the analytical method is in a good agreement with those obtained by experimental measurements and by longitudinal model using finite-element method, where in both two methods the effect of the axial heat flow is taken into consideration. The analytical method gives a simple and easy way to give the conductor temperature profile along the cable joint and other adjacent parts compared with the finite-element method. The dimensions of connector have a great effect on the maximum temperature of cable joint, where the effective parameter in reducing the joint temperature is the connector length. JICABLE15_0252.docx Effect of state of stress on space charge accumulation in silicon rubber insulation in HVDC cables David GUO (1) 1 - State Key Lab of Control and Simulation of Power Systems and Generation Equipment, Dept of Electrical Engineering, Tsinghua University, Beijing, China, david1993k24@gmail.com Silicon rubber has been widely used as the insulation material in the accessory and the terminal of HVDC cables in the last decade. Different from what is used as insulation material in HVAC cables, space charge accumulation in silicon rubber is the main cause of insulation breakdown. Research on space charge in silicon rubber has been conducted for decades and there has already been a lot of achievements about the mechanism, the way to suppress space charge and so forth. Nevertheless, few research pays attention to the stress state of the silicon rubber material, which in practical use is under high stress in the accessory and the terminal of cables. This paper focus on the influence of the high stress state on the space charge accumulation in silicon rubber to imply whether the stress state of silicon rubber should be constrained to a certain scale around the practical value in real HVDC cables in any research concerning space charge accumulation in silicon rubber. Since controlling the stress state of silicon rubber is difficult for most of the current equipment measuring space charge accumulation like PEA systems, this paper also proposes a new design to realize the control of the stress state of the material during measurement in PEA systems. The result of the research shows that both the stress state and the density of the material has effect on the space charge accumulation, and the effect is estimated based on the two standards proposed in the paper. As the density of silicon rubber would change along with the change of the stress state, this paper analyses the research data and makes some calculation to separate the effect of the two factors on space charge accumulation, and finally the result implies a relatively complicated process, not a monotonic tendency as what is expected, which can be taken into consideration in real cable design and in other research about space charge accumulation in silicon rubber. JICABLE15_0253.doc French feedback on civil and installation transmission underground cable systems works of Hervé GUYOT (1), Serge HASCOET, Frédéric LESUR (2) 1 - SERCE, Paris, France, guyot@clichy.spac.fr 2 - RTE, Paris, France, serge.hascoet@rte-france.com, frederic.lesur@rte-france. The number of underground cable systems of long length is growing significantly at RTE - the French transmission system operator - for both HVAC and HVDC circuits. The design and the fulfilment of a project raises various difficulties or challenges as not only the cable route selection, the mean length of elementary cable sections, the length of the civil works allotment assigned to tenderers, the skills adequacy of the contractors performing the cable unwinding and installation, but also the difficulties of acceptance by local residents, and the taking into account of environmental criteria or local employment. The optimisation process is based on the improvement of construction yields and the reduction of the number of joint bays. Nevertheless, the inherent increase of section length must remain compatible with the control of the high voltage cables unwinding and pulling, and complying with the technical reference framework of RTE. Solutions fit with the identified constraints and the limits of technological offers: production capacity of long cable length, drums transportation, unloading and cable pulling. The calculation of cable pulling forces is both a key factor of optimisation and a safety feature ensuring not to exceed the permissible stress. The authors discuss in the present paper the approach implemented in France within the recent years. JICABLE15_0254.doc Measurements of losses on three core submarine power cables Wilfried FRELIN (1), Christophe MOREAU (1), Dag WILLEN (2), Carsten THIDEMANN (2), Volker WASCHK (2), Gabriel de ROBIEN (3), Nathalie BOUDINET (4) 1 - EDF R&D, Moret sur Loing, France, wilfried.frelin@edf.fr, christophe.moreau@edf.fr 2 - nkt cables group gmbh & KG, Germany, Dag.Willen@nktcables.com 3 - EDF-CIST, Saint-Denis, France, Gabriel.de-robien@edf.fr 4 - RTE, Paris La Défense, France, nathalie.boudinet@rte-france.com Submarine power cables are designed with an armour to protect the cable during storage and laying operation but also from external hazards like anchors or trawling gear. The armour is composed of wires, generally steel wires, helically wound around the three-core cables. Such metallic and magnetic armouring provides additional losses when alternating current flows in the cores and thus reduces the cable ampacity. IEC 60287-1-1 gives formulae in order to estimate the armour losses but recent studies highlight that the use of this formulae yield substantial overestimation. The proposed formulae in IEC standards comes from the model developed by Carter in 1928 for three-core cables in a metallic non-magnetic tube and was experimentally extrapolated by Arnolds in 1939 to cover the magnetic behaviour of the armouring. IEC formulae consider that both the core and the armour are laid parallel to each other and doesn’t take into account the cancellation effect provided by the twisting of the components with different lay length. The overestimation of armour losses during the design process leads to the use of larger cables. Thus the development of an accurate formula can lead to a reduction of conductor size and consequently cable size and price. Measurements have been performed in EDF Lab Les Renardières on three-core submarine power cables the last two years in order to address armour losses overestimation, to give comparison data for future implementation in Finite Element Model(s) and to give good measurement protocol to assess armour losses. Two different three-core submarine cables (150kV, 1200 mm²) with copper conductors and a singlelayer armour were considered: the first armour was composed of steel wires and the second armour was made with a mix of PE and steel wires. Measurements were achieved with different currents (close to the rating current) and using various screen connections (single point bounded, grounded at both ends with different impedances). The paper presents the set-up used in order to measure the armour losses and an analysis of the results obtained on the two cable designs. It addresses also the influence of sea water on armour losses by immersing the cable in salt water. Finally results are compared to those given by the application of IEC formulae. JICABLE15_0255.doc Analysis between open cut and trenchless methods for installation of underground high voltage systems. Giovanni CRESTAN (1), Vital BATISTA (1), Jody FUJIHARA (1), Claudimar CHAVES (1), Sanzio KRAUSS (1) 1 : Sedra Engenharia, São Paulo, Brazil gcrestan@hotmail.com, vitalpbatista@gmail.com, jody_fujihara@hotmail.com, claudimarchaves@hotmail.com, sanziokrauss@yahoo.com.br This work aims to analyze the technical and economic characteristics of the open cut method traditionally used in Brazil for construction of underground lines, and a new trend in the country that primarily considers the trenchless method for construction of the entire underground transmission line. It also present proposals and studies aimed at improving construction methods for both cases, making a comparison between the two methods. Traditionally in the country under study, underground transmission lines are built by the open cut method, done by manual or machine excavation, installation of HDPE ducts, backfill and restoration of the original floor, with the main premise of the lowest cost of implementing works. In this concept, only use the trenchless method where it is needed to crossings major roads, rivers, railways, or when there is no permission to dig at the site. However, with new regulations imposed by environmental agencies and the municipalities of big cities, the use of trenchless method as the main method of construction has provided several advantages over the traditional method, such as: facilities for obtaining installation permits, minor teams working in the field, agility during the execution of work and lower social and environmental impact. The trenchless method, also known as directional drilling, is the use of drilling equipment that creates the path through which the pipeline will pass, directly linking the starting point to the exit point of the cables. In this passage, interventions are not necessary on the surface, thus minimizing installation time, inconvenience to traffic of people and vehicles, interference with existing installations and disorders in the execution of crossings structures. In Brazil, the trenchless method is commonly used in urban areas. For this case is a troubling obtain record of the existing interference, which usually present inaccurate and outdated, a site visit is required of registries surveyed, making use of GPR (Ground Penetrating Radar), Pipe Locator, digging wells visits and other relevant techniques to the exact location of the interference to be diverted. The competitive challenge of the trenchless method is demonstrate that its higher cost compared to traditional method will be compensated at the end of the deployment with gains in execution time and ability to avoid major disruptions that arise during the execution of a destructive method, which are difficult to measure in project planning. JICABLE15_0256.docx Installation of twenty-four (24) lines of 150kV XLPE power cables at 2.5 m depth below ground level in the tropical urban city Jakarta John Yuddy STEVEN (1), Ngapuli SINISUKA (2) 1 - PLN Indonesia, Jalan Trunojoyo Blok M 1/135, Jakarta, Indonesia. john.rembet@pln.co.id 2 - Institut Teknologi Bandung, Jalan Ganesha 10, Bandung, Indonesia. ngapuli.sinisuka@stei.itb.ac.id Jakarta as the capital of Indonesia, since 2010 has issued new rules about Network Utilities Placement Procedure, one of its contents about sets out guidelines for the installation of high-voltage cables. Under this law stated that the high voltage cables should be buried at a depth of 2.5 m from the ground level to the top surface of the cable. In order to connect the substation (150kV Tanah Tinggi Substation), required incomer transmission with double-phi configuration (4 circuit) with the number of cables per phase is two (2), so that the total number is twenty-four (24) cables. On first and second circuits, used cables with XLPE insulation and copper conductor 1000 sqmm. On third and four circuits, used cables XLPE insulation and copper conductor 800 sqmm. Installation of this incomer transmission in general use two ducts system, there are box-cluvert and boring systems. For box-cluvert system, cable construction made by eight (8) rack support which each rack containing 3 cables. As for boring system, cable construction made of six (6) cables in horizontal in four (4) stacking. Numerical analysis for cable temperature and ampacitiy that depend on the power load and trench type. At the box-cluvert system, temperature distribution simulated by air circulation, while the boring system based on the thermal resistivity of the protective layer and backfilling material. In general, this paper covers the installation details and results of the analysis for the thermal characteristic and electrical characteristic. Key words XLPE cables; Power cable installation; Cable ampacity; Ducts; Trench JICABLE15_0257.doc New issues in current rating of power cables installed in unventilated tunnels Eric DORISON (1), Wilfried FRELIN (1), George ANDERS (2), Olivier MOREAU (3) 1 - EDF R&D, Moret-sur-Loing, France, wilfried.frelin@edf.fr, dorison.eric@orange.fr 2 - Lodz University of Technology, Poland, george.anders@bell.net 3 - EDF CIST, Dubai, olivier.moreau@edfgroup.ae The current rating of power cables installed in free air is addressed by IEC standards 60287 series: the general formula to calculate the permissible current is given by IEC 60287-1-1. Then external thermal resistance of an insulated cable installed in free air and ratings for groups of cables are described in IEC60287-2-1. Finally IEC 60287-2-2 extends the scope to even larger groups of cables. In these standards, the cables are assumed being of equal diameter and emitting equal losses. Also the ambient temperature is supposed to be known. Moreover, in IEC 60287-2-2, dielectric losses are neglected. In the proposed paper, first, the IEC method for rating cables installed in still air is reviewed and considerations are given to the modelling of various modes of heat transfer with the aim for deriving the IEC formulae as there are no published sources how these equations were obtained. Special attention is paid to the derating factors for groups of cables. With groups of cables the rating of the hottest cable will be lower than if the same cable was installed alone due to mutual heating. A simple method to take into account this mutual heating effect is to calculate the rating of a single cable and apply a reduction factor (derating factor). Some new developments merging the IEC and Siemens approaches to obtain the derating factor for low and medium voltage cables will be discussed. The paper also reviews a method to take into account dielectric losses when deriving reduction factors (presented in a Jicable’11 paper). Then, the paper introduces derating factors for some homogeneous groups of cables which are not considered in the IEC standards. - Large groups of touching cables side by side. Derating factors, derived from tests, are in line with values given by Heinhold for LV cables. Their extension to MV and HV cables is discussed. - Groups of spaced cables side by side Where the clearance between cables is large enough to consider that the convective heat transfer is not affected, derating factors are readily determined from the calculation of the variation in heat transferred by radiation. This leads to the conclusion that the derating is not significant where the clearance is larger than about 0.5 times the external cables diameter for a group of 2 cables, and 0.75 times for a group of 3 cables, as stated in IEC 60287-2-2. The paper also deals with the rating of cables in tunnels, stressing some issues to be considered when applying IEC formulae originally made for cables in still air. A way to take into account the variation of the ambient temperature when increasing the number of cables is proposed, with consideration on the external thermal resistance of the tunnel. Finally, the rating derived using this approach is compared with the FEM calculations on several examples. JICABLE E15_0258.do oc Impro oved de esign for f antii-scatterring in fault c conditio on of outdo oor term mination n M.H. JUN (1), Y.B. KIM K (1), S.G. CHOI (1), J .W. KIM (1) 1 : Iljin E Electric, Repu ublic of Korea. myun nghun.jun@illjin.co.kr, you ungbum.kim@ @iljin.co.kr, soogeol.choi@iljin.co.kr, jinwo oo.kim@iljin.cco.kr As EHV V cable system became e close to o our environm ment, safety comes to vvery importa ant issue. Because e an outdoo or termination is particullarly expose ed to the ou utside, theree could be a greater problem than other te erminations and joints if a breakdown n occur. At th he situation oof breakdown n or other surges, sshort-circuit current is ca aused. It makkes internal arcs a and hea avy inner preessure inevita ably. Due to the inn ner pressure e, broken pieces fly awayy near the terrmination and d can cause secondary damage. d Many ou utdoor terminations are not far from m downtown ns. So dama aged outdooor terminatio ons could become mechanical dangerous explosives. T This issue is s already a problem p in m many countrie es, and it has set u up provisionss to prevent secondary d damage led by b Europe ele ectric power companies. We designed a new type of outd door terminattion for prote ecting from this t secondaary damage. Although breakdow wn of outdo oor terminattion occurs,, the new design d secu ure anti-scatttering. In 2012, 2 we proceede ed anti-scatttering test(internal arc te est) in CESI Italy according to HD6322 S2(2008) standard. s We teste ed on outdo oor terminations for volttage grades s of 170kV and a 245kV. The tests simulated s situation ns of 31.5kA ~ 50kA shorrt-circuit curre ent occurren nce. Test is positive p if theere is not pro ojection of material which constitute insulator at a d distance ove er 3m from object undder test. Tests were successffully completted. Fig. 1 Fig. 2 The paper will give an a introductio on to an anti--scattering te est and items s considered when designed. JICABLE15_0259.docx Online PD monitoring of short cable systems installed in substations Fernando GARNACHO (1), Javier ORTEGO (2), Miguel Ángel SÁNCHEZ-URÁN (2), Alberto GONZÁLEZ (3) 1 - LCOE-FFII, Madrid, Spain, fernandog@lcoe.etsii.upm.es 2 - ETSIDI-UPM, Madrid, Spain, javier.ortego@upm.es , miguelangel.sanchezuran@upm.es 3 - UFD-Gas Natural Fenosa, Madrid, Spain, agonzalezsan@gasnatural.com Acceptance tests on short cable systems installed in substations using conventional mobile generators are very complicated: a) different and special cable terminations must be used to remove the electrical connection with the power transformer, b) the low capacitance of the short cable system does not permit to get an appropriate resonance frequency. Special mobile high voltage generators to compensate reactive power are the most appropriate, but in practice, no acceptance tests are performed on these cables. The consequences of an insulation failure of a cable termination installed in power substation can be very critical. The dielectric insulation health of cables that interconnect power transformers with GIS is important for the equipment integrity and for safety reasons because the high short circuit current existing in power substations. Therefore, on line PD monitoring of these short cables is very convenient. However, some technical issues must be solved to get good insulation diagnosis: a) noise interference level on power substations are often very high, b) many different PD sources can appear coming from many different apparatus (switchgear, voltage and current transformers, power transforms, surge arresters, insulators), c) many different PD patterns must be distinguished associated to different dielectric media (air, paper-oil, solid insulation, etc.) and in dielectric interfaces (air-insulation, oil-insulation, interfaces between two insulations, etc.). This paper describes a complete on-line PD monitoring system installed on short cable systems of substations that permit to perform synchronized PD measurements. PD sensors (HFCT, UHF) placed on the earth connections of the cable terminations are used. Additional HFCT PD sensors installed at the transformer earth connection is also convenient. The methodology to remove the background noise from the measured signals and to discriminate each PD source detected is described in the paper. Using amplitude level, polarity sign, frequency spectrum content and the time delay of the arrival instant of each acquired pulse permits to determine the correct PD source emplacement. The paper also describes some practical experiences in high voltage substations where specific signal processing tools were decisive to get a correct insulation diagnosis. Discrimination of the different sources, identification of the insulation affected and determination of the emplacement of each PD source are crucial for a good diagnosis, otherwise wrong insulation diagnosis can be performed. Many intermittent PD sources appear in high voltage substations, some of them correlated to atmospheric conditions when outdoor substations are monitored. In other cases intermittent PD sources appear after switching operations due to overvoltages provoked and also due to load changes. In consequence, complementary variables supplied by thermal sensors, current and voltage sensors should to be also used to perform an appropriate insulation diagnosis. On line experiences show that the PD evolution of each PD source detected must be analyzed considering two measured parameters: PD amplitude and the PD rate (number PD pulses per period). A reliable noise rejection tool is fundamental to assure a stable PD sensitivity in different noise conditions that can appear in the power substation, in order to obtain coherent PD evolutions of each PD source. JICABLE E15_0259.do ocx Sub bstation HV V / MV HV V GIS CAS MS M MV GIS MV Cable system s HV Cable system m T1 MS MS M MS MS MS MS CAS Con ntrol & Analysis Sysstem MS Meaasuring System PD Sensor Fig g. 1: Online PD monitorin ng system installed in pow wer substatioon. JICABLE15_0260.docx Study of XLPE dielectric properties for HVDC cables during combined thermal and electrical ageing Aurélien HASCOAT (1) (2), Jérôme CASTELLON (1), Serge AGNEL (1), Wilfried FRELIN (2), Philippe EGROT (2), Pierre HONDAA (3), Soraya AMMI (3), Dominique LEROUX (4), Johan ANDERSSON (4), Virginie ERIKSSON (4) 1 - Institut d’Electronique du Sud, Université Montpellier 2, Montpellier, France, aurelien.hascoat@ies.univ-montp2.fr, jerome.castellon@ies.univ-montp2.fr, serge.agnel@ies.univ-montp2.fr 2 - EDF R&D, Les Renardières, Ecuelles, France, wilfried.frelin@edf.fr, philippe.egrot@edf.fr 3 - RTE, Paris La Défense, France, soraya.ammi@rte-france.com, pierre.hondaa@rte-france.com 4 - BOREALIS, Stenungsund, Sweden, dominique.leroux@borealisgroup.com, carljohan.andersson@borealisgroup.com, virginie.eriksson@borealisgroup.com The development of High Voltage Direct Current (HVDC) cables requires specific design and materials with appropriate properties. Cross-linked polyethylene (XLPE) has established itself over the last 30 years as an important insulation material for HVAC cables but also, more recently, for HVDC cables (10-15 years). If the electrical properties of this polymer have been widely studied under AC stress, the behaviour of these materials under high DC stress is less known and needs thorough investigation. In DC conditions, the electric field distribution is strongly dependent on both temperature and electric field. Furthermore, electric field distribution can also be affected by electric charges trapped in the insulating material. Space charge accumulation can increase significantly the local electric field value, thus accelerating ageing and increasing the risk of breakdown. Consequently, understanding the influences of electrical and thermal stresses on the material properties are key factors to improve the HVDC insulation material lifetime. The purpose of the present work is to investigate the evolution of dielectric properties of the XLPE submitted to electrical and thermal ageing. The aim is to improve knowledge about the XLPE ageing under DC conditions and identify possible ageing markers. The ultimate objective is to propose an adapted ageing model, taking into account the applied electric field and the operating temperature. The space charge accumulation will be deeply investigated in order to consider the true electric field acting on the insulation This study is carried out on Rogowski samples made of XLPE insulation with semiconductive electrodes (thickness of 0.5 mm or 1 mm) aged in a oven at three different temperatures (70°C, 80°C and 90°C) and two electric field (30kV/mm and 60kV/mm). After different ageing time, electrical resistivity, dielectric loss factor and space charge accumulation are measured in order to detect a possible evolution of the dielectric properties related to ageing process. During the different analyses, precaution is taken in order to maintain the electrical state of the sample, The space charge behavior and the electric field distribution are investigated using a nondestructive method, the Thermal Step Method. The paper presents the experimental setups and comments the results collected. JICABLE15_0261.doc Compact paperless joint for transition from LPFF to XLPE cables Pietro CORSARO (1) 1 - Brugg Kabel AG, Brugg, Switzerland, pietro.corsaro@brugg.com Network of underground low pressure fluid filled (LPFF) cables is under continuous transformation towards a full solid insulation cables, typically XLPE. There are multiple drivers of such transformation, e.g. aged cables, damage from third parties without spare cable of the same design, ampacity upgrade and many others. For such reason, replacement of LPFF cables may have place mainly in two different ways: either the whole circuit is replaced or only one or few spans of LPFF cables are replaced with XLPE cables with same or larger cross-section. Last approach requires the use of so-called transition joints. Such joints looks typically almost like a back-to-back termination, are quite massive, long and requires jointing skills on both technology paper and XLPE and it is a matter of fact that such skills, for LPFF cables, are less and less easily available on the market. This paper reports about the concept, the design, FEM simulation and developmet test of a new compact paperless transition joint. Such solution has several advantages, the main being the fact that no specific skill for LPFF cables is required: no more hand paper lapping or pencil profiling is required. Such features dramatically reduce time of installation when compared to standard transition joints. The joint is extremely compact and comparable in size with a standard joint for XLPE cables, Such characteristic is extremely important mainly when has to be installed in an urban environment where space constrains for joint bay are extremely demanding. In addition such joint can be factory tested, therefore for quality of installation and reliability of the solution is comparable with joints for XLPE cables. Keywords: Transition joint, paperless, LPFF cables, XLPE cables JICABLE15_0262.doc Performance evaluation of integrity monitoring based on optical fibre distributed temperature and distributed acoustic sensing Chris CONWAY (1), Michael MONDANOS (2) 1 : Bandweaver, 30 Magnolia Court, West Hall Road, Richmond, UK, TW9 4EQ. chrisconway@bandweaver.co.uk 2 : Silixa Ltd., Silixa House, 230 Centennial Park, Centennial Avenue, Elstree, UK, WD6 3SN. michael.mondanos@silixa.com The global Transmission and Distribution network owners and operators have, in recent years, embraced the technical and commercial advantages of installing distributed and point based optical monitoring technologies for continuous monitoring of their cable and substation assets. In the area of distributed temperature sensing, end users have been able to take advantage of the ever increasing distance range, temperature measurement quality and the increasing reliability of such technologies. Such technology provides temperature data to server based Dynamic Cable Rating (DCR) or Real Time Thermal Rating (RTTR) systems. The adoption of these technologies and others within the industry has assisted and promoted the development of new capabilities regarding distributed optical sensing technologies. Distributed Acoustic Systems (DAS) are currently generating much interest in the electrical utility industry. DAS offers a true acoustic response with a fully-representative detection of the acoustic field at typically every metre along a length of fibre. The DAS system is the true analogue to a synchronised microphonic array, and so can be used for beamforming (the phase-shifted addition of acoustic fields measured at different sensing points). This allows us to find the position of acoustic sources relative to the cable, and selectively listen to different points in the acoustic field. It does this by sending an optical signal into the fibre and looking at the naturally occurring reflections that are scattered back all along the glass. By analysing these reflections, and measuring the time between the laser pulse being launched and the signal being received, the system can measure the acoustic signal continuously. The technology measures from one end of a single standard telecoms fibre; there are no special components, such as fibre gratings, in the optical path. The DAS system is so sensitive that it allows digital recording of acoustic fields at every location with a frequency up to 100 kHz at short ranges. It has the capability to be deployed on existing singlemode and multimode fibre optic cable infrastructure. This paper provides an explanation of the general principles of operation of an Intelligent Distributed Acoustic Sensor (iDAS) and focuses on the current areas of interest and applications of this technology within the industry. Currently the technology is mainly used for security monitoring of utility assets and third party intervention monitoring. The paper explores some of current applications with reference to existing installations. This paper also explores and provides information that will enable the potential for future applications e.g. into the area of acoustic monitoring of partial discharge events on distributed assets and locally based assets. We also provide insight regarding how this Distributed Acoustic Sensing technology can be integrated within utility network infrastructure. Key words Distributed Sensing, DTS, DAS, Integrity monitoring, Optical fibre, Asset management. JICABLE15_0263.doc Feedback on the management of transmission lines magnetic fields in France Matthieu CABAU, Frédéric LESUR, Francois DESCHAMPS 1 - RTE, Paris, France matthieu.cabau@rte-france.com, frederic.lesur@rte-france.com, francois.deschamps@rte-france.com Since 2010, almost all of the new 63-90kV circuits are underground links. Major projects at higher voltage level are in progress, such as the southeastern safety net which will be commissioned in December 2014 (three HVAC connected links of 17 + 25 + 65 km at 225kV). This is a representative illustration of the demanding permitting process of transmission lines. When the reluctance to the visual impact has been solved, the management of electromagnetic fields remains the main social - more than environmental - concern. The presentation reviews the main topics of a probably unique background to mitigate decisive obstacles during the selection of the cable route: information and transparency are the keywords of RTE’s action. In 2012, the French government declared the establishment of a monitoring plan of 5000 point database of EMF measurement. The deadline is December 2017, and every circuit transmitting more than 400 A must be checked. The summary sheet (from the complete report) will then be publically available online. RTE is also connected with the mayors of the 36000 French cities. Anybody can request his mayor to get a measurement performed by an independent and accredited organisation. The report is then added to the monitoring plan record set and is available online. Since 2011, a dedicated and exhaustive web site (www.clefdeschamps.info) provides many educational sheets, frequently asked questions, videos, brochures, useful links… A special care is given to a friendly communication, with didactic and interactive games, quiz, and illustrations. A discussion with EMF referents is possible with a forum. The educational sheets present orders of magnitude of EMF values, MF in the environment, MF and health, regulations, official documents, etc. From an engineering point of view, the cable system design (in trefoil formation) is favourable to low values of maximum EMF, well under the regulation values. R&D, calculations, models with finite element method and experimentations are carried out by RTE in order to improve the management of singular points such as junction bays (even if the regulations are already followed. In 2015, a standard solution is developed, that proves to be efficient to divide magnetic field by a factor 2, and fast and easy to install: passive loops of 150 mm² copper cross section, laid on the top of the joint bay, just before closing it. Calculations, model results and site measurements are discussed by the authors in the present paper. Finally, a golden rule as a conclusion: each RTE employee is the best ambassador to make EMF considerations more familiar. About 100 people per year, involved in consultation (permitting process) and project management, follow a two day training course to improve their knowledge in EMF and the relationship with the public. This is a very efficient way to bring the information on the fields. JICABLE15_0264.doc Calculation of the current arrangement in a deep tunnel rating for complex cable George ANDERS (1), Boguslaw BOCHENSKI (2), Gunnar HENNING (3) 1.- Lodz University of Technology, Lodz, Poland, george.anders@bell.net 2.- Kinectrics Inc., Toronto, Canada, Boguslaw.bochenski@kinecrics.com 3. - ABB HV Cables, Karlskrona, Sweden, gunnar.henning@se.abb.com Due to congested infrastructure in urban centres, increasing number of cable circuits is installed in deep tunnels. An analytical model for rating of cables in such installations has been described in the Jicable’11 paper by Dorison and Anders. They observed that due to the soil thermal inertia, a long duration is necessary to reach the steady-state value; thus, instead of using the standard IEC formula for the cable external thermal resistance, a more appropriate approach would be to use the transient analysis algorithm and iteratively find out what value of the current would give desired temperature at the end of the study period. They defined a fictitious equivalent depth of the cable circuit that with the application of the steady state algorithm would give the same value of the current as the one obtained from the transient analysis. The analytical approach discussed in the above mentioned paper is applicable to simple cable geometry. However, in a recent project involving installation of four 230kV cable circuits located in a new concrete tunnel, due to personnel safety of people entering the tunnel for maintenance and inspection, two of the above four circuits will be installed inside ducts embedded in concrete on the tunnel side wall (see Fig. 1 below) or in trough at the bottom floor of the tunnel. The calculation of the current rating of such installations is not easily amenable to analytical approaches. The paper discusses how such installations can be rated and shows the results for ventilated and unventilated tunnel 3 m in diameter 30 m deep. Fig. 1 Cross section of the tunnel installation and the results of the FE analysis. One of the contributions of the paper will be an introduction of a simplified model for the temperature calculations in a ventilated tunnel. The proposed model is shown below. Figure 2 shows heat balance at distance z in the tunnel. The heat dissipated from the cable is transported by the air flow along the tunnel and conducted through the tunnel wall. JICABLE15_0264.doc Fig. 2 Model of a fragment of the cable tunnel The equation for heat balance in the tunnel is: Wo dz ( z ) o To dz d D2 c pa v dt 4 The heat transfer coefficient h at the tunnel wall gives rise to a temperature drop over a transition layer. The temperature drop may be eliminated through introduction of an equivalent thermal resistance Toe. Calculations of this resistance as well as analytical solution to the heat balance equation are discussed in the proposed paper. JICABLE15_0265.docx Derating factors for multiple circuits of low and medium voltage cable installations Boguslaw BOCHENSKI (1), George J. ANDERS (2) 1 - Kinectrics Inc., Toronto, Canada; Boguslaw.bochenski@kinectrics.com 2 - Lodz University of Technology, Lodz, Poland; george.anders@bell.net Electrical engineers who design and supply internal circuits in new buildings often use ampacity tables provided by cable manufacturers. This approach is usually sufficient; however, in certain conditions additional ampacity study needs to be conducted. The aforementioned conditions are applicable to installations where multiple circuits are laid close to each other which can often be observed in modern data centers. Characteristic behavior of such circuits is relatively high power requirement and almost unity load factor. Although the power loss of individual cable chosen on the basis of generic ampacity tables seems to be low, the impact of multiple tens of cables can be easily underestimated leading to overheating and in effect decreasing of the reliability of such facility. As previously mentioned, one of the solutions is to conduct ampacity study for each installation which is impractical and not cost effective. Second approach is to develop de-rating tables for high number (beyond 20) of cables directly buried or installed in conduits. These tables or formulas, if implemented as a standard, will provide guidance for designing such installations. The IEC standards for low and medium voltage cables as well as some published works by Siemens address the issue of derating factors for multi-circuit installations. There is no information given how these factors were obtained and verified. This paper presents the results of calculations performed towards obtaining tables for certain configurations of cables where the engineer can apply the de-rating factor for multiple installations. The approach used in the calculations applies the finite element method (FEM) permitting to overcome the limitations of the analytical methods. In order to validate the approach several simplified FEM models are verified with analytical ones. In summary, the paper will provide the details of the calculations, key factors and a discussion of developing further guidelines. JICABLE15_0266.doc The influence of operating conditions of cable lines in grids on selected properties of extruded cable insulation Jozef Jacek ZAWODNIAK (1), Aleksandra RAKOWSKA (2) 1 - ENEA-Operator S.A., Poznan, (Poland), jj.zawodniak@wp.pl, 2 - Poznan University of Technology, Poznan, (Poland), aleksandra.rakowska@put.poznan.pl Medium voltage cable lines exploited by distribution companies operate in various configurations - in underground power network or in mixed configurations with overhead power lines. Tests of several dozen parts of MV cables with extruded insulation, exploited in real conditions, confirmed that the process of degradation of polyethylene cable insulation depends on the place of work location’ of the cable line in the MV power network. Measurements of thermal properties and resistance to partial discharges, and assessments of molecular molar mass of particular insulation layers were conducted, with the samples of insulation obtained in the way shown in the figure 1. Analysis of the measurement results led to the conclusion that changes in selected properties of the extruded insulation of MV cables exploited in real conditions depend on the kind of the cable network. In cable insulation from the lines work in underground power networks faster deterioration of the physical and chemical properties of insulation is observed next to the return conductor, while in the cable cooperating with the overhead line the destruction processes are more prominent in the insulation next to the return cable. Screen on the conductor Layer no 1 Layer no 2 Layer no 3 Layer no 4 Insulation after removing the semiconductive screen Fig. A way of obtaining of layers of cable insulation for testing As a result of the laboratory tests and analysis of the work conditions of the underground cable lines, it was possible to establish that the process of degradation of polyethylene insulation is influenced by the electrical conditions typical for specific types of cable systems. Next, the factors contributing to fast insulation degradation have been identified. Finally, some recommendations for maintenance services have been formulated, regarding limiting the negative impact of thermal effects on extruded insulation. JICABLE15_0266.doc Example: Budget comparison for alternative approaches The construction of the model will also be examined. The model will be analyzed in detail through the review of input variables, an overview of the actual equations, and the resulting financial and reliability outputs. Based on actual field experience, specific examples in the form of case studies will be shared that demonstrate the resulting value of defect specific diagnostics as both an aging cable asset management strategy and a cable reliability tool. The paper will examine both the financial aspects and the reliability aspects of the examples in the case studies. In summary, the discussion of this model to proactively deal with the problem of aging assets and the resulting decline in cable system reliability should offer affected utilities a way to more effectively evaluate alternatives to improve their system reliability. JICABLE15_0267.docx Improving Cable System Reliability by Monitored Withstand Diagnostics - featuring high efficiency at reduced test time Manfred BAWART (1), Carlos FERRER (2), Joseba Koldo GAMEZ (2), Antoni VILLALONGA (2), Jose Luis FERRERES (3) 1 - BAUR Prüf und Messtechnik, Sulz, Austria, m.bawart@baur.at 2 - Endesa Distribución Eléctrica, Palma de Mallorca, Spain, carlos.ferrer@endesa.es, joseba.gamez@endesa.es, antonio.villalonga@endesa.es 3 - MARTIN BAUR S.A., Barcelona, Spain, joseluisferreres@martinbaur.es Today the medium voltage cable systems are degrading over time and subsequently more failures are recorded. Effective asset management strategies are required to manage the aging underground cable infrastructure. Utilities are forced to improve the cable system reliability by adequate maintenance programs. Commonly voltage withstand tests are applied to test the electric strength of the cable system and thereby determine the voltage withstand performance. This approach is well accepted for new cable installations whereas aged cable systems fail often by unnecessary high voltage stress. There smart cable diagnostic methods take place offering information on cable degrading at reduced test voltage levels. Effective maintenance programs help thereby to renew in time the weak cable accessories or cable sections avoiding the costly replacement of the whole cable. Sinusoidal VLF test voltage is used to avoid unnecessary damages of aged XLPE cables. Thereby well established diagnostic methods are applied providing a deep analyze for estimation of the remaining cable live cycle. Partial discharge measurement (PD) provides information on weak spots especially on electrical treeing phenomena and allows localizing points of degradation. Often weak cable joints or terminations are detected. PD testing also detects weak spots in PILC cables. Field tests by Endesa Baleares over the past years have proven that PD testing is limited to its PD- and electric treeing phenomena. PD testing was found to be limited in detecting the global cable aging condition of old cable installations as often not providing information on fault causes generated by moisture ingress on cable accessories even those are statistically present in the failure cause list. A dissipation factor measurement (tan delta) was found most useful to inform about the global aging condition of the cable. Tan delta ramp up measurements provide a deep analyze of the complete cable circuit. The paper provides first hand information on measuring results of distribution cable systems gained by Endesa Baleares featuring a new tan delta trend monitoring, which provides useful information on cable circuit integrity as well as offers key information to differentiate the pre-fault phenomena. The tan delta trend monitoring provides unique information to judge for high failure risk on wet joints and carbon tracking in joints, terminations and cables. The paper also provides case studies on complex PD and Tan Delta diagnosis of old PILC Hybrid cable circuits. Best practice examples of monitored withstand diagnostics based on PD and tan delta is illustrated. Monitored withstand diagnostics differs from lately introduced monitored withstand testing as it aims to avoid unnecessary electric overstress on old cable installations. This paper further focuses on how to improve the test and diagnostics productivity factor. Latest developments enable to run tan delta and PD measurement simultaneously that provides additional diagnostic information during voltage ramp up and allows trending of PD and tan delta. This features the potential to reduce the time spent on site for cable test and diagnostics drastically and allows an essential time saving of 50%. High efficiency in cables diagnostics and optimizing the time spent on are essential factors for effective asset management strategies. JICABLE15_0268.doc Dielectric Loss Evolution for Miniature Cables with PE Insulation through Various Stages of Degradation Simon BERNIER (1), Jean-François DRAPEAU (1), Daniel JEAN (1) 1 - Institut de recherche d’Hydro-Québec, Varennes, Québec, Canada, bernier.simon@ireq.ca, drapeau.jean-francois@ireq.ca, jean.daniel@ireq.ca PE based insulation has been introduced in underground distribution cable systems up to 40 years ago. For this type of insulation, long term aging is a concern since it is well known that water treeing gradually develops when the insulation is exposed simultaneously to water ingress and service electric stress. As a growing proportion of XLPE extruded cables are considered to be reaching the end of their design service life, there is a need to get a better understanding of the relation between diagnostic measurement results and the “actual” aging condition of the insulation. Insulation degradation can develop according to two processes: global and local. Global aging is related to the development of water trees while local ageing issues may be related to specific defects in the bulk of the insulation (e.g.: protrusions, contaminants, cavities) and to the presence of very long water trees (typically vented) that may lead to the development of electrical trees. The main purpose of this study is to clarify the influence of these types of aging on the actual electrical performance of the insulation and on the development of associated diagnostic features and values, along with the level of aging. The cables used for this study were miniature cables (RG-58) having an insulation thickness of ~1 mm. The aging took place by having the cable samples immersed in tap water and energized at 5kV AC up to ~18000 h. In order to get a portrait of the evolution of the aging condition of the insulation, the cable samples have been assessed at regular intervals, typically every 1000 h to 2000 h. The following items were included in the condition assessment procedure: a) Insulation performance, measured by residual AC breakdown voltage; b) Diagnostic tests; c) Material aging characterization, performed through systematic examination of water trees (bow-tie trees, vented trees) and electrical trees. The diagnostics that were used for step “b” were based on characterization of dielectric losses. Two methods were used: VLF tan delta diagnostic and Time domain spectroscopy (TDS). Condition assessment through VLF tan delta was done using the following diagnostic features: Tan delta mean values @ 2kV (i.e. voltage corresponding to mean service stress - 1 Uo); Voltage dependence (Tip-up) (i.e. difference between TD @ 1.5 Uo and TD @ 0.5 Uo); Time stability @ 1 Uo (measured by standard deviation) Nonlinear voltage dependence (difference in “slope” for TD values between 0.5 and 1 Uo of tan delta (“Tip-up of the tip-up”) and between 1 Uo and 1.5 Uo) Condition assessment through TDS, which shows the evolution of dielectric loss vs frequency, was performed using an experimental device that has been developed at Hydro-Québec (IREQ). Diagnostic features for TDS include dielectric loss spectrum shape, voltage dependence and dielectric loss POL/DEPOL ratios @ 0.001 Hz. The evolution of all these features will be shown and discussed through the various steps of the aging process. Key words Insulation, Dielectric, Water tree, VLF tan delta, TDS, Breakdown voltage, Weibull. JICABLE E15_0269.do oc Use o of confo ormal trransform m for cu urrent ra ating ca alculatio ons of underground d cable systems s s Frédéric LESUR, 1 - RTE, Paris, Francce, frederic.le esur@rte-fra ance, IEC 60287 standard provides me ethods for th he calculation n of the perm missible curreent rating of cables in the cond ditions of ste eady-state op peration (a ccontinuous constant curre ent - 100% lload factor - tuned to produce asymptotica ally the max ximum cond ductor tempe erature, the surroundingg ambient conditions c being assumed con nstant). Formulae are applicable for f cables buried b in a soil consid dered as homogeneous (with a correction to take into account one e duct bank). But when thhe heat path between the hotte est cable and d the soil su urface crosse es areas hav ving differentt values of thhermal resis stivity, the engineerr has to select another method m (e.g. F Finite Element Method), with w an increeased complexity. Thirty ye ears ago, Cigré C Workin ng Group 21 1.02 published a report entitled “Thhe calculatio on of the external thermal resiistance of ca able laid in m materials hav ving different thermal resiistivities” (Ele ectra 98). The metthod is based d on the principle of supe erposition (ca ables and he eat sources aare addresse ed one by one, the e others being unloade ed, then the e mutual efffects are ad dded), combbined with a specific mathema atic tool: the conformal trransform. While the e cross-sectional map off the cables a and soil is a semi-infinite plane wheree Kennelly hy ypothesis is applie ed (figure below on the le eft), the confformal transfform redraws s this map innto a diagram having finite recctangular bou undaries (figu ure on the rig ght). The upp per and lowe er sides repre esent the gro ound and ca able surfaces s respectivel y. In the tran nsformed plane, issotherms beccome lines parallel p to the e line repres senting the ground g surfacce, and flux lines are represen nted by lines perpendicular to the isottherms. JICABLE15_0269.doc Then a meshed Network Analogue is built, taking into account the thermal resistivity of the different materials. From the temperature values of the isothermal upper and lower sides, it is possible to solve the heat equation at each node, the quantity of heat flowing between the reference cable and the ground surface, and the external thermal resistance of each cable, leading back to the conventional IEC 60287 calculation. The author discusses in the present paper the method implemented into a very user-friendly application. The drawing of transformed maps is a didactic approach to assess the influence of each area, and to explain some possible approximations. Case studies are illustrated (soil with several horizontal layers, several circuits in banks or backfills in parallel, concrete troughs filled with sand, heat pipes with insulating plates). They are put into perspective in order to evaluate the error made when only one thermal resistivity is used (simplified assumption of IEC 60287). JICABLE15_0270.docx Online Partial Discharge Testing of Power Cables in High Noise Environment Ammar Anwar KHAN 1 - Qualitrol LLC, 74 Black Street, G4 0EF, Glasgow, United Kingdom aakhan@qualitrolcorp.com Condition monitoring of power equipment is a key tool to ensure their reliability and safe operation. Partial discharge (PD) detection of underground power cable has been proven as one of the reliable techniques of condition monitoring for the purpose of condition based maintenance of power cables. Online PD monitoring is a valuable tool to assess the condition of power cables while in service. This paper will present the case studies conducted in different substations with high noise. Detecting partial discharges (PD) is simple when low background noise or interference is present. However, measurements become practically difficult to extract PD signals from noise. Sometimes, PD signals are much lesser in magnitude than the noise or superimposed onto the noise or interference signals making it difficult for simple pulse location algorithms to extract PD signals. Acquiring data at high sampling rate (greater than100MS/s) and taking the advantage of signal processing techniques, it makes possible to extract PD signals in high noise conditions. Different de-noising techniques are being discussed in literature, this paper will present the techniques that serve the purpose for successful PD testing of power cables along with their implementation in real substation environment. JICABLE15_0271.doc Condition monitoring of electrical Resonance Analysis (LIRA). cables using LIne Paolo F. FANTONI (1) 1 - Wirescan AS,kVeldroveien 7, NO-1407 Vinterbro, Norway, pff@wirescan.no There is a continued interest worldwide in the safety aspects of electrical cable system degradation. Degradation of a cable system can result in loss of critical functions of the equipment energized by the system, or in loss of critical information relevant to the decision making process and operator actions. In either situation, unanticipated or premature aging of a cable can lead to unavailability of equipment important to safety and compromise public health and safety. Current techniques to evaluate aging properties of electric cables include electric properties tests. While known to be difficult, advancements in detection systems and computerized data analysis techniques may allow ultimate use of electrical testing to predict future behavior and residual life of cables. The following describes the current results and development of a system (LIRA) and its progress in being able to determine the degree of cable degradation through electrical testing. LIRA has gone through extensive tests since 2005 with low, medium and high voltage cables, both in laboratory tests and in-situ experiments and it has been used in service assignments since 2007. The LIRA (Line Resonance Analysis) Technology is a cable condition assessment, cable fault location and cable aging management system that works in frequency domain through advanced proprietary algorithms. LIRA is based on the transmission line theory, and calculates and analyse the complex line impedance as a function of the applied signal for a wide frequency band. It detects and locates changes in the cable impedance and makes it possible to perform fault location and cable condition monitoring on I&C, low, medium, and high voltage cables even in inaccessible challenging environments. The applied frequency band is a 5V signal, and is harmless to the cable. LIRA will detect and locate local degradations in the cable, which is specific to certain sections of the cable and caused by mechanical stress and damages, or by heat-induced oxidation and radiation. It will also detect global degradation in the cable, which is applicable for the entire cable, and is caused by general aging, influenced by external and internal environmental conditions. This paper presents the current technology at the base of this system, together with some interesting results on installed cables. JICABLE15_0272.doc Development of Advanced Partial Discharge Measurement for XLPE Cable System Toshihiro TAKAHASHI (1), Yusuke NOZAWA (1), Tatsuki OKAMOTO (1) 1 - Central Research Institute of Electric Power Industry (CRIEPI), Yokosuka, Japan, tosihiro@criepi.denken.or.jp, y-nozawa@criepi.denken.or.jp, tatsuki@criepi.denken.or.jp Background and aim of this paper XLPE cable system is widely introduced in power transmission and distribution system especially in urban area, as well as link lines between power apparatus in substations. It has terminations in its both ends, and joints for long underground transmission lines. Recently, the pre-molded type cable termination and joint are developed and being introduced in the actual power grid, however, prefabricated type cable termination and joint were introduced mainly for around 30 years in Japan and many of them have been still under operation. Such highly-aged prefabricated termination and joint, it is reported that some kind of chemical deposits are formed at the interfaces between different solid materials such as the interface between the stress relief cone and XLPE. The deposits might be a cause of a void at the interface, which might bring about the partial discharge and might lead to the dielectric breakdown. Here, partial discharge (PD) measurement with electrical method is one of the major candidates to prevent that, thus the authors are developing PD measuring technique for XLPE cable. This paper aims to develop the PD measuring technique for XLPE cable applying the foil electrode method and the high frequency techniques. In the paper, the authors introduce the details of the technology and some measuring examples. Two foil electrodes are set on the sheath of test cable with a space of tens millimeter, then they are connected to the high frequency amplifier having wide frequency band up to more than 1 GHz. Using such an amplifier, PD pulse signal with its rise time of several nano-second to several hundred nanosecond can be obtained with high time resolution of sub nano-second order. Foil electrodes and an amplifier The foil electrode consists of a copper or aluminum tape with its width of around 20 mm, which is wound on the cable sheath and rounded tightly. Then it is tightened by a copper wire and is made its end as a signal pickup. Another foil electrode is made with around 10 mm apart from the first one. The amplifier has two signal inlets, so the inlets are connected to the signal pickups of the two foil electrodes. The amplifier has its frequency range up to more than 1 GHz to obtain the PD signal with high time resolution with sub nano-second. This feature can bring us the single PD waveform. The mechanism of the detection will be discussed on the paper. Application of the proposed technique The proposed technique can be applied to PD measurement for the XLPE cable system to detect PD source, as well as flow direction of PD signal. The time difference of arrival for plural measuring point can be realized using plural sets of the foil electrodes and the amplifier, with its time resolution of sub nano-second, ff course an oscilloscope with high time resolution more than 1 G samples per second is required. The detail will be discussed on the paper. JICABLE15_0273.docx Measures to reduce skin-effect losses in power cables with optimized conductor design and their evaluation by measurement Gero SCHRÖDER (1), Volker WASCHK (2), Ronald PLATH (3), Rolf SCHUHMANN (3), René SUCHANTKE (3) 1 - Südkabel GmbH, Mannheim, Germany, gero.schroeder@suedkabel.com 2 - NKT Cables GmbH & Co. KG, Köln, Germany, volker.waschk@nktcables.com 3 - Technical University of Berlin, Berlin, Germany, plath@ht.tu-berlin.de, rolf.schuhmann@tu-berlin.de, such.rene@gmail.com Due to a rising power consumption, HV cables have to carry larger currents. This is done by increasing the conductor’s cross-section and optimizing its design. An improved design decreases the skin effect losses and hence increases the effective cross-section. Nevertheless the AC-losses can reach the DC-losses in recent conductor designs at 50 Hz/60 Hz. Thus, the influenceable AC-losses present a great potential for energy savings. To evaluate recent and future optimized conductor designs, it is crucial to have an efficient measurement method. Previous methods used a calorimetric approach. Heavy currents (often more than 1000 A) drive the conductor into steady state condition, so that no more joule heating occurs. From measuring the temperature one can derive the total losses produced by both DC- and ACresistance. Beside high energy costs and long waiting times (commonly more than 10 hours), bigger cross-sections make it harder to bring the cable into the steady state condition. A much faster and precise measurement method is presented and was already shown in [1]. A small current of only a few ampere is inserted into the inner conductor on one side, and short-circuited with the cable screen on the other side of the cable. By using the cable screen as the return conductor, this setup prevents the proximity effect on cable-drums because no magnetic fields exist outside of the cable screen. The inserted current is frequency variable. To avoid EMC troubles, measurement values around 50 Hz/60 Hz are taken and interpolated for the AC-resistance at 50 Hz/60 Hz. The current is measured with a highly precise reference shunt and used together with the voltage drop over the inner conductor to determine the AC-resistance. In addition to the fully automated measuring, this methods features a plausibility check by measuring the DC-resistance, which can also be calculated analytically and AC-resistances at frequencies up to 10 kHz. The data obtained by the AC-resistances at higher frequencies can be used to gain further insights in the behavior of optimized conductor geometries. This work describes the fundamentals of the new measurement method and furthermore shows how it can be verified by analytical solution for known conductor geometries and numerical simulations for more complex structures. The made observations by both, measurement and numerical simulation can be used to optimize conductors of power cables even more and thus reduce the costs for cable manufacturers. [1] G. Schröder, J. Kaumanns, R. Plath, “Advanced Measurement of AC Resistance on Skin-Effect Reduced Large Conductor Power Cable“, Jicable 2011, paper A.8.2 Keywords: AC measurement, AC resistance, DC resistance, power cables, skin effect, losses, coaxial, frequency variable, proximity effect, cable drums, 50 Hz, calorimetric, JICABLE15_0274.docx Effects of voltage magnitude on growth characteristics of electrical trees in silicone rubber Yunxiao ZHANG (1), Yuanxiang ZHOU (1), Xu ZHANG(2) 1 - State Key Lab of Control and Simulation of Power Systems and Generation Equipments, Department of Electrical Engineering, Tsinghua University, Beijing 100084, China, zhangyxthu@gmail.com, zhou-yx@tsinghua.edu.cn, 2 - North China Electric Power Research Institute Co, Ltd, Beijing 100045, China zhangxu2013ncepri@163.com . With fast development of power cable, Silicone rubber (SIR), as an advanced internal insulating material, has been widely used in high voltage cable accessories due to its excellent insulation and mechanical performance, but there is still a lot of insulation failure. It was told that material aging properties are main reason which influences the operational reliability of cable accessories. Occasionally happened breakdown failures caused by electrical treeing in SIR have threatened the reliability of the super high voltage (SHV) XLPE(cross-linked polyethylene) power cable lines which have been strongly developed to use. In this paper, effects of voltage magnitude on growth characteristics of electrical trees in SIR were illustrated using a digital image acquisition system, by which inception and propagation processes of electrical trees in SIR can be observed. It was found that applied voltage plays a dominate role on growth characteristics of electrical trees in SIR in terms of initiation, morphology and propagation. In trees initiation stage, with increasing of applied voltage, electrical tree initiation probability becomes larger, while tree initiation time dramatically decreases. The experiment observations demonstrated four shapes of trees which are dominated and transferred by the magnitude of applied voltage. Meanwhile, long-term aging experiments under the different voltages were conducted to observe propagation processes, and exponential relationship was found between tree length and magnitude of applied voltage. In addition, electrical trees life-cycles, recurring processes of propagation-stagnation, are also closely related to voltage magnitude. Thus, a growth pattern of electrical trees in SIR was proposed to give a comprehensive understanding of influences of voltage magnitude on morphology. In addition, a mechanism of charge activity was utilized to explain the voltage influences on trees initiation and propagation. Key Words: silicone rubber, electrical tree, voltage magnitude, morphology, long-term aging JICABLE15_0275.doc Aging management for XLPE and EPR medium voltage cables in nuclear plant environments Sarajit BANERJEE (1), Howard SEDDING (1), David ROUISON (1) 1 - Kinectrics Inc., Toronto, Canada, sarajit.banerjee@kinectrics.com , howard.sedding@ieee.org, david.rouison@kinectrics.com Currently, in North America, significant attention is being paid to the condition of cable systems in nuclear generating stations with respect to re-licensing and life extension, including recognition that low voltage (LV) and medium voltage (MV) plant cables are critical to the safe, reliable and economic operation of nuclear power plants. Consequently, the regulators and operators are increasingly focused on the implementation of aging management of low and medium voltage cables in the nuclear environment - especially when one considers 60 year and possibly even 80 year plant life extensions. In US MV Cable Aging Management (AM) programs, Very Low Frequency (VLF) tan delta testing and VLF withstand testing are the most commonly applied field diagnostic techniques, relying on test methods and assessment criteria guidance from the Electric Power Research Institute (Technical Report 3002000557) and IEEE 400.2-2013. Such programs have been successful in identifying cable system defects, particularly those related to bulk water-tree related degradation. In Canadian CANDU (Canada Deuterium Uranium) plants in Ontario, since 1981 a combination of AC withstand and partial discharge (PD) diagnostic methods have been most often applied, for commissioning generating station cable circuits as well as routine maintenance of aged cables at every outage. Such testing has been extremely effective in identifying both gross (bulk) defects as well as localized workmanship related flaws particularly in cable accessories. This paper presents a summary of test statistics and key experiences from 30+ years of nondestructive shielded MV plant electrical cable diagnostics in CANDU plants, and approximately 5+ years in US nuclear stations by Kinectrics and its predecessor (Ontario Hydro Research Division). The contribution also describes an established technical approach for MV cable aging management consisting of: 1. Off-line AC (50 or 60 Hz) over-voltage or withstand testing 2. Off-line Partial Discharge testing using electrical and acoustic methods, including pulse injection measurements to confirm PD sensitivity at terminal ends 3. VLF (0.1 Hz) Tangent Delta Testing 4. Dielectric Spectroscopy Testing - typically obtaining frequency response from 0.01 or 0.1 - 10 Hz at variable voltages (0.5 Uo - 2 Uo) By combining the approaches above, a number of benefits are realized as follows: 1. Technical merits of both power frequency and low frequency methods can be realized 2. Diagnostic measurements can be sensitive to localized latent electrical defects, distributed (bulk) water-treeing related degradation and, in the case of dielectric spectroscopy, to distributed (bulk) thermal aging related degradation. In addition to the above approach, the benefits and limitations of additional evolving diagnostics such as travelling wave based methods (i.e. Frequency Domain Reflectometry (FDR), Frequency Response Analysis (FRA), etc.) will be discussed. These methods are unique in their applicability to electrical diagnostic field terminal measurements on unshielded and shielded, MV and LV cables. However, at the current time there is a lack of research on the fundamental technical basis and acceptance criterion for such techniques. JICABLE E15_0276.do ocx Final Countd down fo or CPR Cable Classific C cation - View frrom a Notifiied Bod dy Christian n CORNELIS SSEN 1 - VDE Testing and Certification n Institute, Offfenbach, Ge ermany, chris stian.cornelisssen@vde.co om In July 2 2013, the ne ew European n Constructio on Products Regulation 305/2011 3 (C PR) came finally into force. But for cables, the applic cation of CP PR rules is still not possible, becauuse there arre still no harmonizzed standard ds based on mandate M4 443 of the Eu uropean Com mmission (sittuation in 11//2014). Cenelec worked on the appropriate standard d and finally issued 2014 4 the EN 505575, which describes d the proce ess of conformity assess sment and th he demands on internal production p asssessment, but b also a lot of otther aspectss like the assignment a o of each fire class with the approppriate test sttandards. Furtherm more, in 201 14, CEN iss sued the EN N 13501-6 standard, s de escribing thrreshold values to be reached in the differe ent tests for obtaining o a ccertain fire class. Neverthe eless, at the end of 2014,, the publicattion (and therrefore harmo onization) of tthese standards in the Official Journal of the European Union U has nott taken place,, but is expec cted to happeen in 2015. Before B this publicatio on, the CPR R cannot be applied forr cables, me eaning that the t different obligations on cable manufaccturers like providing p a Declaration D o of Performance (DoP) an nd therefor aapplying a System S of Assessm ment/Verificatiion of Consta ancy of Perforrmance (asse essment systems) are nott active. The diffe erent existing g assessment systems a are describe ed in Annex V of the CP PR. Figure 1 shows a simplified d overview of obligation ns on manuffacturers an nd so-called Notified Boddies for the systems 1+ and 3 3, which are relevant for cables. c Fig. 1: Systems off Assessmen nt/Verification n of Constan ncy of Perform mance The oblig gations on th he Notified Bodies B shown n in Figure 1 call for a clo ose cooperaation between n Notified Bodies a and manufaccturers, since e in practice,, a lot of detail aspects have h to be co considered fo or testing, inspectio on and certification. On the other h hand, Notifie ed Bodies have to be im mpartial, neutral and independ dent from th he manufacturer. These and also alll other requ uirements forr Notified Bo odies are given in article 43 an nd following of o the CPR. After an overview off the actual status s of CP PR for cables s, the paper will give a sshort introduction into the demands on a Notified Body and their rea alization in practice. p The main part w will relate to the above mentione ed detail aspects during g testing, insspection and d certification n, including some input from the SH02-W WG10, the relevant workin ng group for cables within n the Group of Notified B Bodies. It will cover for example e information concerning f power an nd communiccation cables s EXAP rules for Use of manu ufacturer’s te est facilities Process of conformity c as ssessment Rules for con ntinuous surv veillance / fa actory inspec ction JICABLE15_0001.docx