Ampacity and other design considerations for

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, [email protected]
2 - Consultant, Northboro, Massachusetts, USA, [email protected]
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.
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, [email protected],
[email protected]
2 - Wavin T&I, Dedemsvaart, Netherlands, [email protected]
3 - NKT Cables AS, Brøndby, Denmark, [email protected],
4 - NKT Cables AS, Asnaes, Denmark, [email protected]
5 - NKT Cables AB, Falun, Sweden, [email protected]
6 - Siemens Windpower, Brande, Denmark, [email protected], [email protected]
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
Fig. 1: Overview altern
native system
Fig. 2: Overv
view semi-offffshore trial
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: [email protected]
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.
manent PD
P Mon
nitoring Experiences on
o Sha
anghai 500kV
er cable Lines
JIANG yyun (1),GAO
O Xiaoqing (1),QIAN
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, [email protected]
For the safety opera
ation of a 500kV 15.6 kkm-length po
ower cable line, a permaanent PD monitoring
system w
was installed
d in Septemb
ber 2013. Th
he cable line included 2 circuits
and 6 phases in total,
159 HFCTs and PDDs were installeed on the grounding
147 cablle joints and
d 12 GIS terrminations. 1
cable of each joint an
nd terminatio
on installation
n experience
e and 1 yearr operating experience
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
on, calibratio
on, alarm settting, and PD
D pattern reco
Differentt positions to
o install HFCT sensors are comparred in this paper,
and H
HFCT senso
or on the
ng cable is recognized
a the best sensitivity fo
or PD monitoring. For jooint only with coaxial
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
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
ed system, to find out a relative ca
alibration fac
ctor, e.g. 4.9
9 was mosttly used in Shanghai
Alarm se
etting was another
key issue in Sh anghai 500k
kV cable line
e PD monitooring, and th
his paper
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
ed to the ca
able sealing
g end. PD p
pattern recog
gnition was the most im
mportant too
ol for the
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
With the
e experience
es of PD on
n-line measu
urement for cables, deffects in cabble insulation
n can be
ed in very wid
de range of signal
ency, up to 20 MHz, depe
ending on thee HFCT spec
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
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
in cab
actic foa
am as an
a altern
native electrica
al insula
ation ma
for su
g cable s
Daniel W
LER (1),.
1 - RWT
TH Aachen University,
achen, Germ any, [email protected]
@ifht.rwth-aa, [email protected], schne
[email protected]
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
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
stically. Furtthermore, th
he significan
nce of routiine tests performed
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
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
function.. Additionallyy, solid insula
ation systemss can take mechanical
This pap
per deals witth syntactic foam
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
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
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
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
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
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
lead to lower con
ntractions. By
y filling the polymer
matrrix with 50 pe
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
foam based on
n ER induce young’s mo
oduli of abouut 4000 MPa which is
about ten times higher than the young’s
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
innsulation ma
aterial for
nducting cab
bles and theirr accessoriess like termina
g. 1:.Dielectriic strength of syntactic fo
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, [email protected], [email protected]
2 - Universidad de Los Andes, Mérida, Venezuela, [email protected]
3 - Dow Chemical, Spring House, USA, [email protected], [email protected]
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
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
Repeated field tests - Utility case studies of the value of
Nigel HAMPTON (1), Jean Carlos HERNANDEZ-MEJIA (2), Joshua PERKEL (1)
1 - NEETRAC, Atlanta, USA, [email protected], [email protected]
2 - Universidad de Los Andes, Mérida, Venezuela, [email protected]
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)
This paper will describe
Recent Advances in the deployment of VLF techniques following the release of the updated
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
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, [email protected]
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
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.
Lillebælt - Installation and Commissioning of world’s first
400kV 3-core Submarine Cable
1 -, Fredericia, Denmark, [email protected]
2 - ABB, Karlskrona, Sweden, [email protected]
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
The two 400kV cable systems were commissioned in November and December 2013.
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, [email protected] ,
[email protected], [email protected], [email protected], [email protected]
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.
Installed porcelain
Installed polymeric
Replacement insulator
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
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, [email protected],
[email protected], [email protected], [email protected], [email protected]
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.
Detection of PD pulse and maintenance
▪ 345kV OOT/L (PJ type joint)
√ 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
On the way to compare the polarity reversal withstand
capability of HVDC Mass-Impregnated and extruded cable
Massimo MARZINOTTO (1), Giovanni MAZZANTI (2), Uberto VERCELLOTTI (3), Heiko JAHN (4)
1 : Terna S.p.A., Viale Galbani 70, 00156 Roma, ITALY, [email protected]
2 : Department of Electrical, Electronic and Information Engineering, University of Bologna, Viale
Risorgimento 2, 40136 Bologna, ITALY, [email protected]
3 : CESI S.p.A., Viale Rubattino 54, 20100 Milano, ITALY, [email protected]
4 : FGH Engineering & Test GmbH, Hallenweg 40, 68219 Mannheim, GERMANY, [email protected]
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
Computationally light two-zone moisture migration modelling
for underground cables - critical temperature vs. critical heat
Robert John MILLAR (1), Merkebu DEGEFA (1), Matti LEHTONEN (1)
1 - Aalto University, Espoo, Finland,
[email protected], [email protected] , [email protected]
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  
  
   
qx  W0   i 
 qx ro  dry   wet   dry
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.
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, [email protected]
2 - National Grid Plc, Warwick, UK, [email protected]
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
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
C cable
e rating
g metho
y: therm
mal, ele
ectrical,, and
hanical constra
Ziyi HUA
ANG (1), Jam
RIM (1), Paull L LEWIN (1
1), Steve SW
S (2)
1 - Unive
ersity of Soutthampton, Southampton,, UK, zh2g09
[email protected]
2 - Natio
onal Grid Plc, Warwick, UK,
U Gregory.T
[email protected]
With the
e continuing growth in energy
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
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
to this is thhe need to accurately
know or determine their available ampacity. Therefore, an
a accurate cable rating becomes pa
towards an efficient and
a safe ope
eration of tran
nsmission ne
Besides the standarrd IEC therm
mal-limited ra
ating methodology which follows a maximum conductor
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
considerred by stand
dard rating approaches.. Electrically
y, the dielec
ctric field invversion unde
applications has its maximum electrical strress at the insulation screen,
whicch increases
s with an
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
al stress is very
useful. Mechanicallly, unaccep
ptably high interfacial prressure changes are
reported during loa
ading cycles through th
hermal expansion or co
ontraction. C
y, plastic
deformation of the ca
able sheath can
c occur an
nd dielectric voids might be introduceed. Therefore
e, a rating
ology which prevents in
nternal mech
hanical dam
mage is also
o of great vvalue. Therm
mally, the
al calculation
n loses its applicability
ffor submarin
ne cable cro
ossing ratinggs as some idealistic
assumpttion no long
ger holds (e.g.
isotherrmal ground
d surface). Therefore, numerical modelling
ues become preferable for thermall rating calc
culations es
specially in complicated
d thermal
This pap
per will firstlyy explain, in a comprehen
nsive manne
er, the new rating
methoddology developments
by the a
author to add
dress these challenges.
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
s with approp
priate metho
odology, whic
ch can be beeneficial to both cable
manufaccturers and utilities.
mal rating vs Electrical
ss-limited ratin
ermal rating vs
s Mechanical pressure-limitted rating
The need to update / upgrade test procedures for connectors
used in MV underground joints
1 - NEETRAC, Atlanta, USA, [email protected], [email protected],
[email protected]
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
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
Temperature (C)
Ranked ANSI Performance
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
Numerals reflect different groups of connector installation methods
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
Decision making & forecasting using the data available to
utilities - Pitfalls, challenges and case studies of ways
Detlef WALD (1), Joshua PERKEL (2), Nigel HAMPTON (2),
1 - Eifelkabel, Villmergen, Switzerland, [email protected]
2 - NEETRAC, Atlanta, USA, [email protected], [email protected]
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
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
Review of underground cable impedance and admittance
Akihiro AMETANI (1), Isabel LAFAIA (1), Jean MAHSEREDJIAN (1) and Antoine NAUD (2)
1 -Polytechnique Montreal, Montreal, Canada, [email protected], [email protected],
[email protected]
2 - Reseau de Transport d’Electricite (RTE), Paris, France, [email protected]
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).
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,
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.
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, [email protected]
2 - Demirer Kablo, Istanbul, Turkey, [email protected]
3 - Eifelkabel, Villmergen, Switzerland, [email protected].org
4 - UK Power Networks, Crawley, UK, [email protected]
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
If accepted the authors would like to have oral presentation in section 8 or 4
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, [email protected]
2 - Orton Consulting Engineers International , North Vancouver, Canada, [email protected]
3 - Volsun Electronics, Suzhou, PR China. [email protected]
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
Fig. 1: Picture of a small cable sample undergoing fire testing
Expanding the perfo
e of on site tes
sting wiith frequ
d resona
ant test system
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,
[email protected], kemal.g [email protected]
2 - Moha
aupt High Vo
oltage, Miede
ers, Austria,
[email protected],
[email protected]
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.
Especiallly in case off long lengths and HV orr EHV cable systems the
e usual equippment gets bulky
logistically challengin
ng. Also the setup
time a nd effort for the installatio
on on site m ight be difficult.
per introduce
es the new trend
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
much more light weighted
ent or the po
ossibility of te
esting much
h longer leng
gths compare
ed to existingg testing solutions of
same typ
Fig. 1: F
Frequency Tu
uned resonan
nt Test Syste
em, 350kV, 10A,
10 Hz fo
or On Site Caable Testing
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.
The equ
uipment in usse comprises a 10” con tainer mounted feeder system
and a setup of 4 air core
reactors of extreme high
quality factor.
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
(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.
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
[email protected], [email protected]
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
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
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)
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.
[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
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: [email protected], [email protected] )
2: Prysmian Power Link, Milan (e-mail: [email protected] )
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
coshs    2
sZ c  sr
  sr
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).
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
Frequency dependency of single-core cable parameters
Jarle J. BREMNES (1), Gunnar EVENSET (2)
1 - Unitech Power Systems, Oslo, Norway, [email protected]
2 - Power Cable Consulting, Halden, Norway, [email protected]
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.
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
and indu
uctance is anything
butt straightforw
ward, even when
(possibly) non-lineear propertie
es of the
armour a
are ignored.
The nature of
o HV powerr cables is fa
ar more com
mplex than th
hey are norm
mally given credit
and they ma
ay severely in
nfluence ove rall power sy
ystem properrties.
The finite ellement meth
hod is an exxtremely use
eful analysis tool that haas been far too long
overlooked in everyday electrical
wer engineerring.
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, [email protected]
2 - VISCAS Corporation, Chiba, Japan, [email protected]
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
ctive on
n-site te
esting a
and non-destru
uctive d
sis of
aged (E) HV power
new installed and service
cables up to
Edward GULSKI (1),, Rogier JON
NGEN (1), Ja
arosław PAR
RCIAK (2), Rafael MINAS
SSIAN (3), Alexandra
OWSKA (4),, Krzysztof SIODLA
1 - onsite
e hv solution
ns ag, Luzern
n, Switzerlan
nd, [email protected]
m, [email protected]
2 - onsite
e hv solution
ns Central Eu
urope Sp. Z o
o. o. Warsaw
w, Poland, j.p
[email protected]
3 - onsite
e hv solution
ns Americas Inc, Toronto , Canada, r.m
[email protected]
4 - Pozn
nan Universityy of Technology, Poznan
n, Poland, ale
[email protected],
[email protected]
It is know
wn, that an insulation
faiilure of a pow
wer cable ca
an occur as a result of thhe normal op
voltage or during a transient vo
oltage due to
o lightning or switching surges.
Mosst failures oc
ccur as a
result off localized electrical
are higher than
stresses that a
the die
electric strenngth of the dielectric
materialss in the area of the localized stresss or if the bulk
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
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
testing, p
partial discha
arge detectio
on and dissip
pation factor measurements. Since laast 14 years more
more the
e use of dam
mped AC (DA
AC) energizin
ng is getting worldwide
attention for
1. a
after-laying testing
of new
wly installed cable system
ms, see figurre 1 as well aas
2. m
e and diagno
ostic testing o
of cable syste
ems in opera
which arre fundamen
ntal for the re
eliable opera
ation of unde
erground pow
wer distributtion and tran
Having iin mind the existing IEE
EE 400 and new up-coming IEEE 400.4
Guidee for Field-T
Testing of
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
practicall examples.
Figure 1: Exa
ample of a DA
AC after-layiing test of a 6.4 km long 110kV XLPE
E cable circuit.
Expanding the Perfformanc
ce Poten
ntial of the Uniiversal Cable
em by the use
e of Do
ow END
02 EC
Water Tree Retardan
nt Cross
slinked Polyethylene In
n CREE (1), Christian
1 : Dow Electrical & Telecommun
nications, Ba
sse 3, Horgen, Switzerlannd, CH 8810.
[email protected]
2 : nkt ca
ables AB, Ka
allviksvagen 18, Falun, S
Sweden, SE-7
791 29.
[email protected]
3 : Dow Electrical & Telecommun
nications, 40 0 Arcola Rd.., Collegeville
e, Pennsylvaania, PA 19426, USA.
[email protected]
4 : nkt ca
ables AB, Ka
allviksvagen 18, Falun, S
Sweden, SE-7
791 29.
[email protected]
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
cable o
or overhead line is very different.
wever the us
se of nkt’s
al Cable Sysstem is begin
nning to blurr this differen
nce as the Universal
cabble system has
h been
shown to
o work equa
ally well whetther installed
d overhead on
o poles, or buried undeerground or even
in a
ne environm
ment. Clearlly the adva
antage of using
the same type oof cable in multiple
ments, lowerrs investmen
nt and mainttenance cos
sts while delivering a neew and cost effective
method ffor 12-36kV power distrib
d problems for
f grid owne
ers with ove
erhead lines are e.g. falling trees, snnow loaded trees
ice loadss. Falling trees due to storms may ca
ause perman
nent failure that
must bee addressed with high
priority. Besides gre
eat expense, these incid
dents cause
e poor and hazardous
working enviironment.
Snow loads can make trees and
d branches ccome into co
ontact with wires.
These occasions generates
heavy and time conssuming work
kload, with lo
ong downtim
me as a resu
ult. Heavy icee and snow loads on
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
Recentlyy nkt cables AB has prod
EC (C-4
4202), the new
ed performa
ance water tree
nt crosslinkeed polyethyle
ene (TRXLPE) in
nsulation fro
om Dow Elec
ctrical & Tele
ations. The Universal
caable cores ha
ave been
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 excellent rretained breakdown perfformance of the cable cores with
wn values well
w in excess
s of Cenelec requirementts (6 cables > 18kV/mm or 6 > 14kV
V/mm, 4 >
m and 2 > 22
Figure 1
1: Retained breakdown voltage of n
nkt cable co
ores based upon
Dow E
C following Cenelec
0 Hz accelerrated wet ag
ging test.
Cable lifetime data generated by Dow E lectrical & Telecommun
nications coonfirms the excellent
ance of mediium voltage (MV)
cables made with C-4202.
Figure 2 shows ttime to failure
e data for
full size 15kV MV ca
able subjectted to the Acccelerated Cable
Life Te
est (ACLT) pprotocol. As Figure 2
es, cables made
with C--4202 show significantly
y increased time
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
EC); app
proximately 2,500
days versus
350 d
days. To date the new en
nhanced TR
R-XLPE insulation has
nced only one
e failure at more
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
onductive inssulation shie
elds work
onally well wiith C-4202 in
nsulated cab
bles and nkt cables AB is
s able to em ploy this com
in Universal system cable
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
tree reetardant
Long lengths
s transm
mission power cables on-site testing up to
V by dam
mped AC
A voltag
Paul P. S
SEITZ (1), Ben QUAK (1), Edward G
GULSKI (2), Manuel
D (3), Frank DE VRIES (4
1 - Seitz Instrumentss AG, Niederrohrdorf, Sw
witzerland, bq
[email protected], [email protected]
2 - onsite
e hv solution
ns ag, Luzern
n, Switzerlan
nd, [email protected]
3 - Stuttg
gart Technical University
y, Stuttgart, G
Germany, ma
[email protected]
4 - Liand
don B.V, Alkm
maar, The Netherlands, [email protected]
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
its acceptance ffor:
 q
quality contro
ol of cable and accessor ies installatio
on during afte
er-laying testting,
 m
e testing during operation
n or in conjun
nction with re
epair work affter a failure,
 ccondition asssessment of service aged
d cable circu
In additio
on to the equ
uivalence of sinusoidal d amped AC voltages
(in the
t frequency
cy range of 20-300Hz)
ed to the 50((60) Hz netw
work stressess the charac
cteristics of the applied ttechnology meets
ation of an on
n-site testing
g system:
 L
Lightweight modular
 C
Compactnesss in relation to the outpu
ut voltage,
 L
Low effort fo
or system ass
 L
Low power demand,
even for long ca
able lengths,
 L
Low level noises and
d possibilityy of sensittive PD de
etection andd dissipatio
on factor
In this co
ontribution th
he newest mo
obile solution
ns for DAC field
testing up
u to 500kV oof cable leng
gths up to
25 - 40 km will be presented.
A an innova
ation to the existing
single side (E) H
HV DAC sys
stems for
ng long lengtths and for PD
P detection on longer ca
able lengths compact higgh power sou
urces with
an additiional range extension
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
and ddiagnosis exttender for
Figure 1: Example off a 300kV DA
nsmission ca
able circuits
long tran
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, [email protected], [email protected]
2 - onsite hv solutions ag, Luzern, Switzerland, [email protected]
3 - Liandon B.V, Alkmaar, The Netherlands, [email protected]
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
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,
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
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
Figure 1: Example of a DAC and VLF testing of 36kV XLPE cable circuits.
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, [email protected] [email protected],
[email protected]
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
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.
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)
Non-contact surface metrology
screens in XLPE cables
Jorunn HOELTO, Kristine BAKKEN, Sverre HVIDSTEN (1)
1 - SINTEF Energy Research, Sem Saelands vei 11, Trondheim, Norway
[email protected]
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
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
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,
[email protected], [email protected], [email protected]
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
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,
[email protected], [email protected], [email protected]
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.
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
[email protected], [email protected]
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
∙ exp
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 ∙
and the LIRV indicator is defined as a ratio of
to the amount of intensities of the short-lived
to the total area of the short-lived component
In both cases the multiplying factor and the modulus sign is introduced for the convenience of applying
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
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.
Developpement of a XLPE insulating with low peroxide byproducts
Mohamed MAMMERI (1), Isabelle DENIZET (1), Jean-Christophe GARD (1)
1 - General Cable, Montereau, France,
[email protected] ,[email protected], [email protected],
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.
Assessing smoke and heat release during combustion of
electric cables using cone calorimeter
1 - Central Power Research Institute, Bangalore, India,
[email protected], [email protected]
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
Lethal combustion product evaluation of polymeric materials
used in Power cables
1 - Central Power Research Institute, Bangalore, India,
[email protected], [email protected]
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,
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, [email protected]
2: PE-International, Stuttgart, Germany, [email protected]
3: DNV GL, Arnhem, The Netherlands, [email protected]
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
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.
Dielectric diagnosis of extruded cable insulation by very low
frequency and Spectroscopy techniques - A few case studies
1 - Central Power Research Institute, Bangalore, India,
[email protected], [email protected]
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
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
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, [email protected]
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.
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, [email protected] , [email protected]
2 -, Erritsø, Denmark, [email protected] , [email protected]
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
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
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 and Dong Energy.
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
[email protected], [email protected] , [email protected],
2 :VISCAS corporation, Hiratsuka, Japan
[email protected]
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.
Improving performance of medium voltage cables heat shrink
Saudi Electricity Company, Buraydah, Qassim Area [email protected]
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
Key words
Fault Analysis, Cables Accessories, Heat Shrink, Medium Voltage
Hybrid energy transfer lines with liquid hydrogen and
superconducting cable - first experimental proof of future
power lines.
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.
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, [email protected]
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
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: [email protected]
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, [email protected]
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.
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, [email protected],
[email protected], [email protected], [email protected]
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.
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
[email protected],[email protected], [email protected]
2 - P&M Cable Consulting LLC WTC II Geneva Switzerland [email protected]
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
DC electrical conductivity in LDPE-based nanocomposites
Anh T. HOANG (1), Love PALLON (2), Dongming LIU (2), Carmen COBO SANCHEZ (2)
[email protected], [email protected], [email protected], [email protected]
Ulf W. GEDDE (2), Stanislaw M. GUBANSKI (1), Yuriy V. SERDYUK (1)
[email protected], [email protected], [email protected]
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.
anced medium
e cable ratings by imp
proving cable
ch desig
gn and th
hermal c
Sander M
(1), Abd
dulla Ahmad Mohd AL AGHBARI (2)), Maryam AL
NEAIIMI (2), Muha
annad Rizik Mahmoud A
ASHAAR (2), Mohd Arf Ali ALABBAD
DI (2)
1 - DNV GL, Arnhem
m, The Netherlands,
[email protected] , [email protected]
2 - DEW
WA, Dubai, Un
nited Arab Emirates, Abd
[email protected] ,
[email protected] , Muhan
[email protected] ,
[email protected]
Due to increasing power
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.
pansion of tthe cable ne
etwork is
d mainly due
e to space lim
mitations in tthe city of Dubai.
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
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
materialss. Moreover,, the backfilling material should be made
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
ations, the optimized cable tre
ment and la
ay-out. It als
so describess the
ary quality control and
es to en
nsure prop
per fabrica
transporrtation and installation of
o the backffilling
material.. As expeccted, it is shown
that the
e of moisturre and the magnitude
off the
dry density have an
a importantt impact on
n the
de of the thermal resistivity. It was
ed that loca
ally available crushed rock
ed with red dune
sand, with a minim
dry den
nsity of 210
00 kg/m3 an
nd 1% moissture
content w
will lead to a thermal res
sistivity of aro
1.0 km/W
Finally, an existing cable trench has been selected as
s pilot proje
ect to partly replace the
e existing
ng material by the prop
posed backffilling materiial. Tempera
ature measuurements ha
ave been
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
ch confirms tthe improved
d thermal
conductivity of the ba
ackfill material.
ct of HV
ble Conffiguratio
on on Compass
s Deviattion
Sander M
(1), Stephen HE
EMPHILL (2)), Mick MCG UCKIN (2)
1 - DNV GL, Arnhem
m, The Netherlands,
[email protected] , ro
[email protected]
2 - Mutual Energy, Belfast,
[email protected] , m
[email protected]
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
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
1. a
application of
o one of the
e HV conducctors as LV return condu
uctor, achievving a single
e 250MW
monopole (a
as an emerg
gency fall ba
ack in the ev
vent of simultaneous LV
V cable faults
s on both
2. iinstallation of
o new sepa
arate LV Ca
ables to rees
((using the exxisting HV an
nd new LV);
500 MW dual monopole operation
3. a
amendment of the conve
ertor station ccontrols for bipole
operattion, at 500M
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
onductor, th
return co
he magnetic fields inducced by the current in th
he high-voltaage and low
w voltage
ors mostly cancel
each other. How
wever, by ch
hanging the cable syste m configura
ation to a
n with a new
w external re
eturn conducctor, theory shows
a pottentially signnificant chang
ge in the
magneticc fields, depe
ending on th
he exact loca
ation of the new
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.
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
Finally, tthe installatio
on of new se
eparate LV ccables was selected
as the
t preferredd solution forr reasons
of redu
undancy and
d transmiss
sion capaci ty. With th
he validated
d theoreticaal models, different
ations were investigated
d to optimize
e the locatio
on of the LV cables. Of course, the distance
n the existing
g HV and new
w LV cable p
plays a significant role. Therefore,
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
to gget approval for final
uration and operation
of the Moyle In
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, [email protected]
2 - Norwegian University of Science and Technology, Dept. of Electric Power Engineering, Trondheim,
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.
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, [email protected]
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.
How to perform a pre-qualification test - interpretation of the
Edwin PULTRUM (1), Wouter SLOOT (1), Cor EILANDER (1), Alphons BAAS (1), Gu BIN (1)
1 - KEMA Laboratories, Arnhem, the Netherlands, [email protected]
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.
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, [email protected]
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.
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, [email protected], [email protected]
2 - Furukawa Electric Co., Ltd., Tokyo, Japan, [email protected],
[email protected]
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 &
Floating Structure
Floating Substation
(66kV/22kV substation / observation tower)
Conductor screen
XLPE Insulation
Insulation screen
Metallic screen
Metallic Sheath
Inner jacket (PE)
66kV Submarine
66kV Riser
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
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, [email protected]
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.
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, [email protected], [email protected],
[email protected], [email protected]
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
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.
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,
[email protected]
2 - Viscas Corporation, 4-12-2 Higashi-Shinagawa, Shinagawa-ku, Tokyo 140-0002, Japan,
[email protected], [email protected], [email protected]
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.
3-core XLPE
3-core SCFF
3-core XLPE
compact designed
Fig.1 Cable dimensions in duct
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.
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.
ence off the screen/a
armour permea
ability in mag
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, [email protected],
[email protected]
2 - Energ, Fre
edericia, Denmark, [email protected]
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
arch, for diffe
erent reasons
s, is the maggnetic field generated
by cable
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
out for magnetic fie
elds as the ca
A secon
nd reason iss the overes
stimation of the losses in submarin
ne cables. S
Several partties have
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
of the armour in the magn
netic field
ed by the cab
ble is the ma
ain reason fo r the overesttimation. Res
search is currrently being made by
Aalborg University and
Energin for th
he developm
ment of new analytical fformulae capable an
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
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
ment of accu
urate formula
ae for the thre
ee-core case
Besides comparing the
t results fo
or the differe
ent scenarios
s, fitting apprroximation of the results, with the
onding fitting error, will also be provid
ded with the magnetic
permeability, frrequency, cu
urrent and
geometrry as variable
The obta
ained resultss will help understandin
ng the reaso
ons for the overestimatio
on of the los
sses and
indicate the aspects that should receive
e attention in
n the develop
pment of new
w analytical fo
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, [email protected]
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;
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, [email protected],
[email protected], [email protected]
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.
System Impedances for Power Cable Umbilicals
Kristian Thinn SOLHEIM, Jens Kristian LERVIK (1)
1 - SINTEF Energy Research, Trondheim, Norway, [email protected], [email protected]
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.
Use of aluminium conductors in submarine power cables
Thomas WORZYK (1), Sonny LÅNGSTRÖM (1)
1 -ABB AB, High Voltage Cables, Karlskrona, Sweden, [email protected],
[email protected]
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.
n of an extruded
d HVDC cable system
at 525kV
Anders G
ON (1), Marc
E (1), Hosse
ANI (1), Tobiaas QUIST (1),
R (1), Andrea
S (1), Fredrik AXELSSON
N (2), Vincentt MONDIET (2)
1 - ABB AB, High Vo
oltage Cables
s, Karlskrona
a, Sweden, anders.h.gus
[email protected],
[email protected], hossein.gho
[email protected], tobia
[email protected],
[email protected], and
[email protected]
2 - ABB AB, Kabeldo
on, Alingsås, Sweden, fre
[email protected]
[email protected]
d HVDC cab
ble systems represent a field for which
there are
a high exppectations on
o further
ment of the technology to
t enable futture cost red
duction in po
ower transmiission of larg
ge power
over long distance. Since
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
ogy. The 320
0kV level is enabling
a trransmitted power
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
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
an ad
dopted cable
e manufactu
uring techno
ology. Expeeriments ha
ave been
ed using a va
ariety of test samples ran
nging from plates
to mod
del cables annd full-scale cables. A
major drriving force has
h been to achieve
a hig
gher resistiv
vity of the ins
sulation comppound. The non-filled
XLPE insulation syystem implied that w
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
The full sscale cable system
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
The 525
5kV extruded
d DC cable system
can transmit at least 50% more
power oover longer distances
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
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, [email protected], [email protected]
2 : TAG Inovação Tecnológica, São Paulo, SP, Brazil, [email protected],
[email protected], [email protected]
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
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:
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
 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.
Thermal capability of the XLPE power cable jacket under fault
Chinh DANG (1), Saleman ALIBHAY (2), Jacques CÔTÉ (3)
1 - Hydro-Québec Technologie, 1800 boul. Lionel-Boulet, Varennes, Québec, CANADA, J3X 1S1,
[email protected]
2 - Hydro-Québec Équipement, 800 boul. de Maisonneuve E., Montréal, Québec, CANADA, H2L 4M8,
[email protected]
3 - Hydro-Québec Distribution, 140 boul. Crémazie, Montréal, Québec, CANADA, H2P 1C3,
[email protected]
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.
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, [email protected],
[email protected], [email protected]
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.
Accelerated Alumin
num Co
n upon
n Waterr Ingres
ss in
aged Lo
ow Volta
age Unde
nd Powe
er Cable
Bart KRU
UIZINGA (1)), Peter WOU
UTERS (1), F
Fred STEENNIS (2,1)
1 - Eindh
hoven University of Technology, Eind
dhoven, The Netherlands
s, [email protected],
[email protected]
2 - DNV GL - Energyy, Arnhem, The Netherlan
nds, [email protected]
Low Volttage (LV) un
nderground power
cabless generally have
a good reputation iin terms of customerc
a slow but steady grow
minutes--lost and ageing phenom
mena. Howe
ever, in the Netherlands
wth in the
number of faults is observed.
nce the incre
easing penetrration of de-c
central geneeration is add
ding more
e and given
n the high costs
ed with rep
pairing faults
s, condition monitoring is under
ation. Due to
o the low volltage level, o
often occurring damages
s don’t necesssarily lead to a fault
directly. Damaged cables
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
show the
e presence of
o white powd
der, indicatin
ng corrosion.
For corro
osion to occcur, three ele
ements are rrequired. A metal,
potential differencce and an electrolyte.
When a cable is dam
maged and water
can rea
ach the cond
ductor, these
e elements aare all present. In this
n, aluminum oxide is formed on the surface of the
m. Due to thhe voltage hydroxide
concentrrates at the surface of the conducto
or, causing a dissolution of the oxidee layer. This
s process
allows co
orrosion to continue
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
ed to nomina
al voltage. Th
he process i s recorded by
b a camera, taking pictuures periodic
cally, and
current m
nts are taken at the same
e time. Differrent paths in current flow have been identified,
ng on cable damage and
d type. Initial tests were conducted
ver up to threee weeks of time
for a
single sa
ample. An exxample is giv
ven in figure 1. Several configuration
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
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,
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
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
This worrk reveals the
e often found
d, but hardlyy understood process as it occurs undderground. Corrosion
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.
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, [email protected]
2. - Hellenic Cables, Athens, Greece, [email protected]
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
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
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.
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).
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.
Hydro-Québec Advancements with Infrared Imaging for the
Maintenance of the Underground Medium Voltage Cable
Michel TRÉPANIER (1), Jacques CÔTÉ (2)
Hydro-Québec, 800 140 boul. Crémazie, Montréal, Québec, CANADA, H2P 1C3,
1 - [email protected]
2 - [email protected]
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
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”.
Alireza FARAHANI (1) George J. ANDERS (2), Wouleye KAMARA (1), Emmanuel BIC (3), Uwe
1-CYME Int. - EATON Corp., Montreal, Canada, [email protected],
[email protected]
2-Lodz University of Technology, Lodz, Poland, [email protected]
3-General Cable, Montreau, France, [email protected]
4-AP Sensing, Boeblingen, Germany, [email protected]
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 jt; j  1,..., N with N  t   the total time interval (usually 24h). The optimization problem
can be formulated as follows:
  j t , 
j 1
,  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
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
Alireza FARAHANI (1), George J. ANDERS (2), Laure GAROUX (1), Wouleye KAMARA (1),
1-CYME Int. - EATON Corp., Montreal, Canada, [email protected], [email protected],
[email protected]
2-Lodz University of Technology, Lodz, Poland, [email protected]
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 
 
 
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.
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
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,
[email protected], [email protected]
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.
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, [email protected]
2 - SK chemical, Daejeon-si, Korea, [email protected]
3 - KEPCO, Kwang-ju, Korea, [email protected]
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
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.
Space charge distribution in XLPE plates with non-uniform
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, [email protected],
[email protected], maria.lun[email protected], [email protected],
[email protected]
2 - ABB AB, High Voltage Cables, Karlskrona, Sweden, [email protected],
[email protected]
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.
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, [email protected]
2 - ABB AB, Corporate Research, Västerås, Sweden, [email protected]
3 - Borealis AB, Stenungsund, Sweden, [email protected],
[email protected]
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.
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, [email protected],
[email protected], [email protected], [email protected], [email protected]
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.
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, [email protected]
2 - Lumiker, Bilbao, SPAIN, [email protected]
3 - UFD, Madrid, SPAIN, [email protected]
4 - UFD, Madrid, SPAIN, [email protected]
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.
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,
[email protected]
2 - MARINTEK, Department of Structural Engineering, Trondheim, Norway,
[email protected], [email protected]
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
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,
[email protected], [email protected]
2 - The Norwegian University of Science and Technology (NTNU), Department of Electric Power
Engineering, NO-7465 Trondheim, Norway, [email protected]
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.
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.
[email protected]
2 : Dow Electrical & Telecommunications, 400 Arcola Rd., Collegeville, Pennsylvania, PA 19426, USA.
[email protected]
3 : Dow Electrical & Telecommunications, 400 Arcola Rd., Collegeville, Pennsylvania, PA 19426, USA.
[email protected]
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
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.
Figure 1:: Cable Insullation Dissipa
ation Factor a
as a Function
n of Insulation
n Type and W
Wet Aging Tim
Dissipation Factor (%)
Time (weeks)
Figure 2:: “4202” TR-X
XLPE Cable Ageing;
Dissi pation Factor versus Tem
Figure 3:: Cable Dissip
pation Factorr at 100°C as a Function of
o Electrical Stress
Aging time (D
Figure 4:: Dielectric Sttrength as a Function of A
Aging Time and
n Type while Aging in Wa
ater with a
Conductor Temperatu
ure of 105°C.
dissipation factor (%)
Figure 5: Cable Dissipation Factor Following 1095 Days Ageing in Water
Urban 220kV Cable Transmission: Perpetual Developments
Arvind Kumar Sharma, Vikas Sonar, Sanjeev Bagde, Vikrant Patil
1 - Reliance Infra Ltd., Mumbai, India,
[email protected], [email protected],
[email protected], [email protected]
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.
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.
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.
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
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.
This paper will act as a guide for helping power engineers to build underground Transmission network
in crammed cities of developing countries.
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, [email protected], [email protected],
[email protected], [email protected], [email protected],
[email protected]
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.
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, [email protected],
[email protected] , [email protected]
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.
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, [email protected], [email protected],
[email protected], [email protected]
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
Refinement in ambient temperature selection for current
rating calculations
Frédéric LESUR, Victor LEJOUR
RTE, Paris, France, [email protected], [email protected],
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
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
 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.
e Joint to
P Cables
s for Pro
al Repa
air with Quick
Geraldo R. de Almeida (1), Gil Va
asconcellos (2), Felipe Talhofer
1 - Techsys Cables Inc., Brazil, [email protected]
2 - Matrix Energia, Brazil,
[email protected]
3:- Light SESA Braziil, [email protected]
The use
e of FFLP ca
able "low pre
essure fluid ffilled" was diiscontinued during
'90s iin this counttry due to
lack of ttechnological developme
ent in cabless and compo
onents and hard
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
ment that alllows to sign
nificantly red
ducing assem
mbling time of 138kV F
FFLP strait jo
oint: with
elimination of lead welds
to close
e the casing, pre-manufa
acture of paper notches, cconductor co
made m
mechanically without prressing. Ena
abling assembly and reclose
at lleast 6 hou
urs. This
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
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
the pre
e-fabricated notches appear to
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
Fig - 2 assembl edjoint after IEC 60141 tests
The figure above is a complete view
of the asssembled strrait joint after treatment aand before te
esting AC
T. The most important
art is shown at
a the ends of
o the joint w
where one ca
an see no
and IMP
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"
constitute a suubstantial pa
art of this
Key word
ds Cables, Underground
, Joint, Asse
embly, Provis
sional repair, Contingency
oring Le
ead Allo
oy Solde
er on Cable
oints forr Fluid Filled
Low P
Pressurre 145kV
V with In
ng Press
sure Cla
Geraldo R. de Almeida (1), Paulo
o Deus de So
ouza (2), Carlos Cesar Barioni
de Oliiveira (3) ;
er Pinheiro (4
1 - TECH
HSYS CABLES, Brazil [email protected]
AULO Brazil, [email protected]
3 - DAIM
MON Brazil , [email protected]
4 - TAGP
[email protected]
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
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
ustrated for 1ev)
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
sible types off reinforceme
ents were
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
After the
e tests betwe
een [0, 1000]] on [1,10,10
00 and 1000]] stations hou
urs. The dataa has been treated
us abacus and
extrapolated to 50
00,000 hours
s [50 years] and otherr values. Th
he same
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
Cables, Underground
d, Joint, Assembly, Plum
mbing Solder Reinforceme
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
Available standards for the cable diagnostic
Loss of diele
ectric sttrength of polym
mers at glass trransition due
to hig
uency vo
oltages in HVDC applic
Matthiass BIRLE (1), Carsten LEU
U (1)
1 - Technische Unive
ersität Ilmena
au, Research
h Unit High-V
Voltage Tech
hnologies, Ilm
menau, Germ
[email protected], carsten.leu
[email protected]
This pap
per deals witth the dielec
ctric stress a
and breakdow
wn voltage of
o polymer innsulation ma
aterials in
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
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
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
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
ature higher then glass trransition tem
Further high-resolution current and voltage
e measurem
ment signals during the glass trans
sition are
ed. Thus a sinusoidal
gh-frequencyy voltage is used with co
omplex calcuulation the change
the relattive permittivvity and the
e resistance of the sam
mples is calc
culated baseed on RC - electrical
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.
pared to high
h-frequency voltage stresss the measurements
and calcculations sho
ow that the change
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
Fig. 1: m
measured tem
mperature of the sample and change of permittivitty and resistaance during glass
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,
[email protected], [email protected], [email protected]
2 - Wuhan University, Wuhan, China, [email protected]
3 - Wuhan Power Supply Company, Wuhan, China, [email protected], [email protected]
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.
Phase A
Metal Shield
Phase B
Phase C
Grounding box
Cross-bonded connection
Grounding box
Fig. 1: CT location in cross-bonded XLPE HV cable system
uction, installa
ation an
nd com
mmissioning off two 380kV
d lines for the
e Pump
ge Plan
nt proje
ect of
Linth Limme
ern (Swis
ss Alps))
Claude B
nd Christian MOUCHANG
Nexans Suisse SA, CH
C 2016 Corrtaillod
[email protected], christian.mouch
[email protected]
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
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
The diffe
erent challen
nges of the project lie in the fact that
the 380
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
ment, and th
he required work
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
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
Fig.1a Loadin
ng of the laying bench
on the
e cable car lo
Fig.1b 380kV cablee installation
in the tunnnel
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 - [email protected] ,
[email protected] , [email protected]
2 - SPAC agence Clichy, 13 rue Madame de Sanzillon 92110 Clichy France - [email protected] ,
[email protected]
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
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
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, [email protected] , [email protected]
2 - Netz Burgenland Strom GmbH, Eisenstadt, Austria, [email protected]
3 - UtiLX Europe GmbH, Bückeburg, Germany, [email protected]
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.
Medium voltage cables, PE-insulated cables, life time, refitting of PE-cables, water trees
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,
[email protected]
2 : Prysmian S.p.A , [email protected]
3. Prysmian S.p.A Champs sur Marne -Marne la Vallée France, [email protected]
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
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; [email protected]
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
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
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, [email protected] ,
[email protected] , [email protected] , [email protected]
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.
Long-term experiences and review with offline and online PD
measurements on-site on EHV XLPE cable systems 330kV to
Andreas WEINLEIN (1), Ulrich PETERS (1), Gero SCHRÖDER (1), Dominik HÄRING (1)
1 - Südkabel GmbH, Mannheim, Germany, [email protected] ,
[email protected] , [email protected] , [email protected]
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
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.
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
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.
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; [email protected]
2 - Ing.-Büro HPS Berlin, Germany; [email protected]
3 - Electronics - Web and More GbR, Germany; [email protected]
4 - Balfour Beatty Utility Solutions, United Kingdom; [email protected]
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
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.
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),
1 - Statnett SF, Cable Technology Department, Oslo, Norway, [email protected] ,
[email protected]
2 - Nexans Norway AS, Oslo, Norway, [email protected], [email protected],
[email protected]
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
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.
Development Process of Extruded HVDC Cable Systems
1 - Südkabel GmbH, Mannheim, Germany, [email protected]
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.
Life Cycle Assessments of Extruded AC and DC Power Cable
Dominik HÄRING (1), Gero SCHRÖDER, Christoph SAAM, Andreas WEINLEIN, Axel BOSSMANN
1 - Südkabel GmbH, Mannheim, Germany, [email protected]
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
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.
mal Ratting Me
ethod o
of J Tu
ubes us
sing Fin
nite Ele
ysis Tec
ALE(1), Priank CANGY ((1), James PILGRIM(1)
1 - Tonyy Davies High
h Voltage Laboratory, Un
niversity of So
outhampton, Southamptoon, UK,, jp
[email protected]
[email protected], [email protected]
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
as it
passes tthrough the J tube of an offshore plattform. This section
of the
e cable routee may often present
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
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
a typical J tube. Th
he J tube is comprised
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
he individuall phases from
3) A
Above the offfshore platfo
orm, where th
m the export cable are se
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
Below sea
s ea level,
b ut below
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
te mperature within
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
and the J tube cross sectional area.
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.
[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
Cables for Oil, Gas and Petrochemical Industry
Arun THOMBRE (1), Bahaa MOURAD (1)
1 - DUCAB, Dubai, UAE, [email protected], [email protected]
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
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
Lead sheathed cable
Poly-amide sheathed cable
Protection against
Bending radius
Little larger
Smaller as compared to lead
sheathed cable
Electrical conducting path
for earth fault
Yes, available
No, not available
Number of layers
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.
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, [email protected]
2 - Hellenic Cables SA, Marousi, Greece, [email protected] , [email protected] r
3 - G&W Electric Company, Shanghai, China, [email protected]
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.
oved Method
d Cables
w Tarnowski
Institut d
de recherche d’Hydro-Québec, 1800 B
Blvd. Lionel Boulet, Varennes, Qué, C
Canada J3X 1S1,
[email protected]
The imp
proved meth
hod for determining the mechanicall bending prroperties of undergroun
nd cables
ed in this paper
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
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
t and corresponding
ding force as a function oof time
Displacement (mm) / Force (N)
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
ned in this manner arre underestimates and lead to an
n unsafe
ment of asso
ociated forces—for exam
mple, the pulling forces or
o the therm
al forces.
ally, the test procedure described i n this public
cation does not providee usable datta on the
on of the cable after bend
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
(Figure 1b):
ding: stiffnesss parameterrs of the cablle are assess
axation: relaxxation param
meters are as sessed
Each of these stepss requires its own analytiical model fo
or data analy
ysis and inteerpretation. Since
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
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,
is expresssed as an exponential curve, which
h is depende
ent on a single parametter characterrizing this
on over time. This parameter can be interpreted as
a the time t for which tthe ratio of measured
momentss at time t and
at the beginning
of the relaxatio
on stage is 1 e . A moree accurate relaxation
model w
with two para
ameters is also
propose d. The pape
er describes the models developed and their
application in experim
mental determining of the
e bending properties of underground cables.
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, [email protected], [email protected]
2 - Beca Pty Ltd, Brisbane, Australia, [email protected]
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.
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, [email protected],
[email protected], [email protected], [email protected]
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.
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
[email protected] & [email protected]
2 - Cable Consulting International, PO Box 1, Sevenoaks, Kent, TN14 7EN, UK
[email protected]
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;
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
[email protected]
2 - Cable Consulting International Ltd. PO.Box 1, Sevenoaks, Kent, TN14 7EN, UK
[email protected] & [email protected]
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
Key words
XLPE cables; Separate Pipe Water Cooling;
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
[email protected]; [email protected]; [email protected]
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.
High voltage XPLE cable partial discharge localization
technology based on high frequency signal transmission
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. [email protected], [email protected], [email protected]
2 : State Grid Electric Power Research Institute. No.143 Luoyudong Road, Wuhan City, Hubei
Province, China. [email protected]
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
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. [email protected] , [email protected], [email protected]
2 - State Grid Electric Power Research Institute. No.143 Luoyudong Road, Wuhan City, Hubei
Province, China. [email protected]
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
Key words
XPLE cables; Transmission characteristics; Electromagnetic wave; Signal attenuation
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, [email protected]
2 - Wildash Consulting Limited, Paraparaumu, New Zealand, [email protected]
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.
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, [email protected]
[email protected] , [email protected]
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.
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
BJ(Jo) LE ROUX, (1), JJ(Jerry) WALKER,(2)
1 - Vaal University of Technology, Vanderbijlpark, Gauteng, [email protected]
2 - Visiting Professor, Vaal University of Technology, Vanderbijlpark, Gauteng,
[email protected]
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
The study on the transient electric field distribution of HVDC
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, [email protected] , [email protected] ,
[email protected] , [email protected]
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
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,
[email protected]
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
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.
Research on error control of optimal computation combining
temperature field with ampacity of cables under complicated
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.
[email protected], [email protected], [email protected], [email protected]
2 - State Grid Electric Power Research Institute. No.143 Luoyudong Road, Wuhan City, Hubei
Province, China. [email protected]
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
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, [email protected]
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
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
Design and Analysis of High Current Heat Cycles Test Set for
Underground Cable
1 - Metropolitan Electricity Authority (MEA), Thailand, [email protected]
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
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
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, [email protected]
2 - LS Cable&System Ltd., Gumi, South Korea, [email protected]
3 - LS Cable&System Ltd., Doha, Qatar, [email protected]
4 - DNV GL, Arnhem, The Netherlands, [email protected]
5 - DNV GL, Singapore, [email protected]
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.
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, [email protected]
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
nt and modelin
ng of su
urface charge a
on insulators
s in HVD
DC gas insulate
ed line (GIL)
Boya ZH
HANG (1), Qiiang WANG (1), Guixin Z
1 - Tsing
ghua Universsity, Beijing, China,
[email protected], wqtsi [email protected],
[email protected]
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
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
lines, ga
as insulated line
(GIL) is an
a optimum technology for
f bulk electric power traansmission at
a high or
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
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
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
n on the insullators in GIL has to be re
evisited for fu
uture HVDC aapplications.
For this purpose, a surface
charrge measure
ement system
m is established using thhe electrosta
atic probe
method based on a 220kV
GIL unit. The surfface charge distributions
on a cone-tyype insulatorr made of
Al2O3 fillled epoxy re
esin are obttained underr different vo
oltage duration, voltage polarity and
d voltage
des. Some ph
henomena is
s studied in th
his paper and the possible sources oof surface cha
arges are
hile, a simula
ation model is used to ccalculate the surface cha
arge accumuulation and stationary
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
ding gas inclu
uding the charge carrierss’ generation
n, drifting, rec
combination aand diffusion
With this paper, the authors would
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
for the design and op
e: Distribution
n of surface potential on the GIL insu
ulator under negative
DC voltage
Development of a 500kV PPLP MI cable system for HVDC
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,
[email protected] , [email protected] , [email protected] , [email protected] ,
[email protected] , [email protected] , [email protected]
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
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),
[email protected] , [email protected], [email protected]
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.
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,
[email protected] , [email protected]
2 - Maillefer Extrusion Oy, Ensimmäinen Savu, 01510 Vantaa, Finland,
[email protected] , [email protected]
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
Research and Development of ±320kV Flexible HVDC Power
Ming HU (1), Shuhong XIE (1) Xiaowei WU (1)
1 - Zhongtian Technology Submarine Cable Co., Ltd, Nantong(China), [email protected] ,
[email protected] , [email protected]
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.
Testing the Allowable Compressive Limit of HVAC Submarine
Ahmed M. REDA (1,2), Alex Kwang Hwan OH (3), Peter VAN DER WIELEN (4),
Gareth L. FORBES (2)
1 - Qatar Petroleum, Doha, Qatar, [email protected]
2 - Department of Mechanical Engineering, Curtin University, WA, Perth, Australia,
[email protected]
3 - LS Cable & System Ltd, Seoul, South Korea, [email protected]
4 - DNV GL - Energy, Arnhem, The Netherlands, [email protected]
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.
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
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, [email protected] , [email protected]
2 - SHOWA-TBEA (Shandong) Cable Accessories CO., LTD. Xintai City, Shandong Province, China,
[email protected]
3 - TBEA Shandong Luneng Taishan Cable CO., LTD. Xintai City, Shandong Province,
China, [email protected]
4 - EXSYM Corporation, Sagamihara City, Kanagawa Province,
Japan, [email protected]
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.
500kV, XLPE cable accessory, pre-moulded one piece joint, factory expansion technology
The space charge charac
c in DC
C-XLPE cable after
V PQ tes
Tomohikko KATAYAM
MA(1), Takanori YAMAZ
ZAKI(1), Yoshinao MURA
ATA(1), Shoj i MASHIO(1),
oshi IGI(1), Naohiro
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
[email protected] (Tomo
ohiko Kataya
ama), [email protected]
anori Yamazaki), [email protected]
p (Yoshinao Murata), [email protected]
(Shojji Mashio), ig
[email protected]
p (Tsuyoshi Igi)
2 - Toyohashi Univerrsity of Techn
nology, 1-1 H
Hibarigaoka Tenpaku-cho
o Toyohashi--shi, Aichi-ke
en 4418580, Japan, [email protected] (Na
aohiro Hozumi)), m11120
[email protected] (Masah
hiko Hori)
In recen
nt years, hiigh voltage DC (HVDC
C) cross-link
ked polyethy
ylene powerr cables ha
ave been
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
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
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
onal standarrds if space change
umulation wo
ould affect the deterioratioon of cable insulation
in DC u
use and the
erefore residual space change me
easurement might be uuseful to check the
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
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
to ev
valuate any cchange or increase of
space ch
hange accum
mulation by polarity
reverrsal operation
n after a long
g term test.
V PQ test
Fig. 1 View of 400kV
Fig. 2 Layout of 400kV
PQ teest
Partial Discharge Measurements in the Sub-VLF-Range
Prof. Kay RETHMEIER(1), Rudolf BLANK(2)
1 - Kiel University of Applied Sciences, Kiel, Germany, [email protected]
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.
A Rodent’s dilemma: To chew a cable or not to!
Ms. Varsha POTE (1), Assistant Technical Marketing Manager
1 - C Tech Corporation India
[email protected]
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
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
Keywords: Polymer applications, Rodents, Pests, Non-toxic, Non-hazardous, Green technology
Zanzibar Interconnector 132kV Submarine Cable in Tanzania
Yoshiharu NAKAMURA (1), Masanori OTA (1), Robert DONAGHY (2)
1 - VISCAS Corporation, Tokyo, Japan, [email protected], [email protected]
2 - ESB International, Dublin, Ireland, [email protected]
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.
Study of the behaviour of a n-metal cable screen subject to
an adiabatic short-circuit.
1 : Grupo General Cable Sistemas SL, Casanova 150, 08036 Barcelona, SPAIN.
[email protected]
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
Toward acoustic detection of partial discharges in high
voltage cables.
Monash University, Melbourne, Australia, [email protected]
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.
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, [email protected]
2 - RWE Deutschland AG, Essen, Germany, [email protected]
3 - Karlsruhe Institute of Technology, Karlsruhe, Germany, [email protected]
4 - Nexans SuperConductors GmbH, Hürth, Germany, [email protected]
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.
Development of submarine
Aluminum conductor
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), [email protected], [email protected], [email protected],
[email protected]
2 - General Cable, Manlleu, Barcelona (Spain), [email protected]
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.
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, [email protected]
2 - Prysmian Group, Delft, the Netherlands, [email protected]
3 - Anders Consulting, Toronto, Canada, [email protected]
4 - Elia Engineering, Brussels, Belgium, [email protected]
5 - Electrical Consulting Engineers, Schenectady, USA, [email protected]
6 - University of Southampton, Southampton, UK, [email protected]
7 - Procable, Sao Paolo,Brazil, [email protected]
8 - NKT Cables, Köln, German, [email protected]
9 - Prysmian Group, Milan, Italy, [email protected]
10 - ABB, Karlskrona, Sweden, [email protected]
11 - LS cable Ltd, Gyeongbuk, Korea, [email protected]
12 - Poznan University of Technology, Poznan, Poland, [email protected]
13 - Prysmian Group, Gron, France, [email protected]
14 - CRIEPI, Nagasaka, Japan, [email protected]
15 - Brugg cable, Brugg, Switzerland, [email protected]
16 - Aberdare Cables, Port Elizabeth, South Africa, [email protected]
17 - GasNatural Fenosa, Madrid, Spain, [email protected]
18 - National Grid, Warwick, UK, [email protected]
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:
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.
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.
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
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.
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, [email protected]
[email protected] ; [email protected]
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.
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
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
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,
[email protected], [email protected], [email protected]
2 - General Cable Sistemas, Manlleu, Spain, [email protected]
3 - University of Exeter, Penryn, UK, [email protected], [email protected]
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
Degradation Mechanism of SCOF Cable Due to Cable Core
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, [email protected],
[email protected], [email protected]
2 - J-Power Systems Corporation, Osaka, Japan, [email protected],
[email protected]
3 - VISCAS Corporation, Tokyo, Japan, [email protected], [email protected]
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.
CIGRE WG B1.34: Mechanical Forces with Large Conductor
Cross Section XLPE Cables
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, [email protected]
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 -, 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.
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,
[email protected], [email protected], [email protected],
[email protected],
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 105C
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
Key words
Submarine cable; Keystone conductor; Seismic design; Copper wire armor; Armor Clamp
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, [email protected]
2 - Lumiker, Bilbao, SPAIN, [email protected]
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.
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
[email protected], [email protected],
[email protected]
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
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.
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, [email protected]
2-Walmet Technologies (Pty) Ltd, Vereeniging, South Africa, [email protected]
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.
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
1 - Grupo General Cable Sistemas, S.L.U., Manlleu, Spain, ngene[email protected]
[email protected]
2 - Prysmian Spain, S.A., Vilanova i la Geltrú, Spain, [email protected],
[email protected]
3 - Top Cable, S.A., Rubí, Spain, [email protected]
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.
Sander M
EN (2), Misch
R (3), Jos W
Evertt DE HAAN (5)
1 - DNV GL, Arnhem
m, The Netherlands, sand
[email protected] , peter.vanderw
[email protected],
[email protected], [email protected], [email protected]
Nowadays, network operators are facing cha
allenges in managing their grid effectivvely and in meeting
range off increasing stakeholder
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
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
easures beco
omes more relevant by thhe day.
Among tthe substantial amount and
a diversity of undergro
ound power cables
foundd in modern electricity
networkss, each having its speciffic inherent a
ageing behav
viour and failure impact, the asset manager's
ge is to decide which cable circuits req
quire attentio
on first and what
actions need to be taken.
To give a
asset manag
gers insight into the requ ired long-terrm maintenan
nce and repllacement acttivities an
ed health indexing and risk assesssment mode
el for underg
ground pow
wer cables has
ed and imple
Based o
echnical Broc
chure 358 - Remaining Life
L Managem
ment of Exissting AC und
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
Carlo ssimulations the model
is able to determine a certaiinty level to
o the
The mod
del uses da
ata from a variety
of so
such as cable syste
em specific data:
age, ra
loading data, short--circuit curre
ents, failure data
and cond
dition data; and
a more general data: ty
ageing trrends and fa
ailure statistic
cs. In case d
data is
missing or inaccurrate, deducttion modelss and
al inference are used to provide best
es. The mod
del provides
s clear overrviews
and visu
ualizations for
asset managers
to help
them ovversee the health deve
elopment off their
overall a
asset base down
to each individual cable
circuit in detail.
Modern network ope
erators use a risk-based asset evalu
uation to sup
pport decisioon making. Therefore,
one nee
eds to estim
mate the imp
pact of a cab
ble failure and
e all circuits on the bas
sis of the
g risk. Thereffore, in an additional
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
risk per cable ci rcuit. Relate
ed risk matrix plots visuaalize the various risk
results. This all ena
ables clear and
ed overviews
s for asset managers
too support ap
actions a
at the right tim
Study of the
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, [email protected], [email protected] , [email protected]
2 - Laboratoire IMP, UMR 5223, Villeurbanne, France, [email protected] ,
[email protected]
3 - SuperGrid Institute, Villeurbanne, France, [email protected] ,
[email protected] , [email protected]
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
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. [email protected],
[email protected], [email protected],
[email protected], [email protected],
[email protected]
2 - Prysmian Cavi e Sistemi SRL, Viale Sarca 222, 20126 Milano, ITALY.
[email protected]
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
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.
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. [email protected],
[email protected], [email protected],
[email protected], [email protected],
[email protected]
2 - Prysmian Cavi e Sistemi SRL, Viale Sarca 222, 20126 Milano, ITALY.
[email protected]
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
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.
Risk on failure, ba
ased on
n PD measurem
ments i n actua
al MV
PILC and XLPE pow
wer cable
Yizhou Q
QIAN (1), Pa
AARS (2), Frred STEENN
NIS (3), Denn
N (4), Piet
PBOER (5), Pascal BLEE
EKER (6)
1 - Technical Universsity Eindhove
en, Eindhove
en, the Nethe
erlands, [email protected]
2 - DNV GL, Arnhem
m, the Netherrlands, paul.w
[email protected]
3 - DNV GL, Arnhem
m, the Netherrlands, [email protected]
4 - Allian
nder, Arnhem
m, the Netherrlands, [email protected]
5 - Enexxis, Arnhem, the Netherla
ands, piet.soe
[email protected]
6 - Locamation, Enscchede, the Netherlands,
[email protected]
Many pa
apers discusss partial disc
charge (PD) a
activity as measured
 d
during an offf-line test in actual
MV po
ower cables or
 o
over time, ass measured during
atory circums
Seldomlyy, actual PD developmen
nt is measure
ed as a func
ction of time under
servicee circumstan
nces, and
certainlyy not (often) under service condition
ns until an actual
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
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
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
and P
PILC cables is mixed. It shows
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
a ccertain PD ge
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
failure fo
or one the ca
ases (blue do
ots in the leftt graph).
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), [email protected]
2 - China South Power Grid International Co., Ltd, Guangzhou(China), [email protected]
3 - Shanghai Jiao Tong University, Shanghai (China), [email protected]
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.
Lightning Impulse test requirement for HVDC transmission
Henrik JANSSON (1), Thomas WORZYK (1)
1 -ABB AB, High Voltage Cables, Karlskrona, Sweden, [email protected],
[email protected]
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
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.
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. [email protected]
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
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, [email protected]
2 - Enexis, Arnhem, the Netherlands, [email protected]
3 - Alliander, Arnhem, the Netherlands, [email protected]
4 - Locamation, Enschede, the Netherlands, [email protected]
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
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.
und power ca
ables - return
n of experien
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,
[email protected]
m, cornelis.p
[email protected],
[email protected],,
[email protected], fra
[email protected], fred.steennis
[email protected]
For man
ny years alre
eady, DNV GL’s
branch on operation
nal excellenc
ce (formerly known as KEMA),
performing failure an
nalyses on all
a types of power equip
pment. On a regular bassis also und
power ca
ables are being investiga
ated after havving failed. An
A investigation is normaally focused on
o finding
the root cause, but behind
this ro
oot cause find
ding, there are
a drivers as
avoiding futu
ure failures by
 a
o having a better design,
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
(in order to prrevent outag
ges and rela
ated safety problems, costs
utation issues
 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
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
during servicce operation?
 w
which com
mponents did
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,
AC cable,
DC ccable, paperr
iinsulated cab
ble, extruded
d cable, …. e
 w
what are the
e most com
mmon root ca
auses? This
will be treatted only for cases in w
which is nott
possible to link a spec
cific failure tto a certain
ccable manuffacturer, netw
work owner o
or other third
The fina
al aim of this paper is to proviide concise
information, based
d on the described return off
nce, to netwo
ork owners, cable
acturers and
third parties like installation co
ompanies wo
orld-wide to
avoid similar mista
akes leading
g to a redu
uced failure
probabiliity and thuss increased reliability o
of the cable
Figure 1 - void in the insulation material
an extrude
ed HV cablee, causing inttense PD
activity du
uring the facto
tory acceptan
nce test.
Measurement of the conductor temperature in power cable
Henning FRECHEN (1), Gregor BRAMMER (2), Ralf PUFFER (1), Armin SCHNETTLER (1)
1 - RWTH Aachen University, Aachen, Germany, [email protected], [email protected], [email protected]
2 - Forschungsgemeinschaft für Elektrische Anlagen und Stromwirtschaft e.V., Mannheim, Germany,
[email protected]
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.
Temperature 52°C
Temperature 64°C
Temperature 76°C
Temperature 90°C
Outer Semicon
Inner Semicon
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.
Transducer position in mm
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
ection and ac
ccurate location of faults ((full breakdo
owns) in
Smart Cable Guard - introducing on-line dete
MV ccables
Paul WA
A (2), Denny HARMSEN (3), Pascal B
4), Fred
1 - DNV GL, Arnhem
m, the Netherrlands, paul.w
[email protected]
2 - Enexxis, Arnhem, the Netherla
ands, tjeerd.b
[email protected]
3 - Allian
nder, Arnhem
m, the Netherrlands, [email protected]
4 - Locamation, Enscchede, the Netherlands,
[email protected]
5 - DNV GL, Arnhem
m, the Netherrlands, [email protected]
For seve
eral years Sm
mart Cable Guard
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
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
at booth sides of the
t cable
etected, givin
will be de
ng accurate location posssibilities (like
e with PD’s, also
for faults
ts it is 1% of the cable
length). But there arre more adv
vantages of detecting faults in this way.
A traveelling wave is
i always
there, independent on
o the system grounding
g or type of fault.
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
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
Fig 1: PD
D activity me
easured by SCG
as a fun
nction of time
e (x-axis: cab
ble length; y--axis: time; z-axis: PD
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,
[email protected], [email protected], [email protected], [email protected],
[email protected]
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
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,
[email protected]
2 - EPRI 1300 West WT Harris Boulevard, Charlotte, NC 28221, USA [email protected]
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
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.
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, [email protected],
[email protected]
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
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.
[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.
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
[email protected]
2 : ERDF Direction réseau - 102 terrasse Boieldieu - 92085 Paris la défense CEDEX, France
[email protected]
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
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.
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
[email protected], [email protected]
2 : Institute of Polymer Technologie Friedrich-Alexander-Universität Erlangen-Nürnberg,
Am Weichselgarten 9, Erlangen, Germany
[email protected], [email protected]
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
Key words
HVDC cables; Field inversion; New materials; Thermal conductivity
mating the losses in th
hree corre subm
marine p
power cables
g 2D and
d 3D FEA simullations
an STURM (1
1), Frank BE
ERGER (2), JJohannes PA
AULUS (1), Karl-Ludwig
1 - Unive
ersity of Applied Sciences Würzburg--Schweinfurt, Schweinfurrt, Germany,
[email protected], Jo
[email protected]
2 - Ilmen
nau Universitty of Technology, Ilmena u, Germany,, [email protected]
3 - Nordd
deutsche Se
e GmbH /Ge
eneral Cable, Nordenham
m, Germany,
[email protected]
Several recent publications hav
ve described
d and discus
ssed the losses in the aarmour of th
hree core
ne power ca
ables; espec
cially in the ccase of large
er cables, th
he losses seeem to be lo
ower than
ed with the IE
EC 60287 sta
Thereforre, this paper further inve
estigates the
e losses in co
onductors, shields, and aarmour on th
hree core
ne power ca
ables utilizin
ng a comme
ercial FEA to
ool. Models were set u p using the Maxwell
ns to calcula
ate the joule
e losses in conductors and losses
s caused byy induced circulating
currents as well as eddy curre
ents in surro
ounding metallic compon
nents. 3D m
models were used to
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
onding 2D models
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
were pe
A compa
arison was made
of the simulated
lossses in the cable
s against the losses acco
ording the
d. An overvie
ew of the los
sses in armou
ur, shield an
nd conductors is given. T
The results id
dentify an
on of lossess in the com
mponents an d it can be summarized
d that the suum of the calculated
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
ower cables
ds: IEC 6028
87-1-1; armou
ur losses; thrree core sub
bmarine powe
er cable; FEM
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, [email protected] , [email protected] , [email protected] ,
[email protected]
2 - DIAEL, Madrid, Spain, [email protected]
3 - Prysmian Cables and Systems, Barcelona, Spain, [email protected]
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
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.
Design studies for French submarine links
Nathalie BOUDINET, Jean CHARVET, Matthieu DORY, Emmanuelle LAURE, Vincent MOINDROT,
Frédéric LESUR
1 - RTE, Paris, France,
[email protected], [email protected], [email protected],
[email protected], [email protected], [email protected]
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
ating and qua
g reliability imp
provem ents off new
e design
ns - a ca
ase stud
dy of 600
0 v self sealing
Chris FL
LETCHER (1), Joe Mc AU
ULIFFE (2), & Joshua PE
1 - Duke
e Energy, Charlotte, USA
A, [email protected]
2 - South
hwire, Carrollton, USA, Jo
[email protected]
3 - NEET
TRAC, Atlanta, USA, jos
[email protected]
Manufaccturers continue to mak
ke and utilitties continue
e to deploy new cable designs to address
nt technical and
a reliability
y problems. These new solutions are
e tested in thhe laboratory
y through
ment and ap
pproval tests
s. Although tthe deploym
ment begins only when aall of these tests are
ed to the sattisfaction of all involved; there is still a need to verify
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
increases the scale
(generally by length of product) and
a exposess the solution
n to the ill-de
efined rigors of service. However,
h absolutely essential,
onitoring perf
rformance in service is a challenging undertaking..
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
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
to be part of the normal operration of the utility such that stock & training
vvariables do not interfere
n Bias (an ab initio perce
eption of go
ood or poor performance
e) can overw
whelm the
desired signa
Once the efffectiveness of
o the new ssolution is co
onfirmed upgrading the ccontrol population can
prove to be a logistical and philosoph
hical challeng
Thus, offten the only practical wa
ay forward iss to deploy in
n areas and compare perrformance with
w a non
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
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
study was underttaken on th
he Duke
Enerrgy system using their 6600 V cable
e system.
The final connection bbetween re
omers and
d the prrimary und
distrribution system is madee using low
w voltage
0 V) unsh
hielded cabbles (often termed
“secondary” cables). These low voltage systems
can often be damaged
duuring or so
oon after
allation as bu
uilders and laandscapers complete
theirr construction work. Som
metimes this damage
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
manufacturerrs have ap
pproached t his
Cable m
problem in a coup
ple of ways
s: (1) tough
insulation materialss and (2) self-sealiing
insulation (Figure 6)). The exam
mple studied in
this pa
aper involves the transition fro
al 600 V insulations to a self-sealiing
This pap
per will discuss an effec
ctive analyticcal
solution using the
e Crow / AMSAA
Figure 6: Self-Sealing
g Cable
ology using the seconda
ary cable
case study from Dukke Energy. In
n particular th
he paper will describe:
Issues faced
d in verifying new cable ssolutions
AA technique for Performa
ance Evaluattion
Overview of Low Voltage
e (600 V) Cab
ble Designs
Why Low Vo
oltage Cable Systems Fa il?
Results of Duke Energy Case Study
a. Data
a from multi-y
year pilot stu
b. Initia
al performance prediction
c. Com
mparison of predicted
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
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, [email protected]
2 - EDF R&D, Clamart, France, [email protected]
3 - EDF CIST, Saint-Denis, France, [email protected]
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.
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, [email protected], [email protected]
2 - UNIBO, Bologna, Italy, [email protected], [email protected]
3 - EDF SEPTEN, Villeurbanne, France, [email protected]
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
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.
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, [email protected]
2 - SYCABEL, Paris, France,
3 - ERDF, Paris La Défense, France, [email protected]
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
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.
However, it shall be necessary to improve tools to guaranty these results on the network.
* Members of Sycabel :
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, [email protected], [email protected], [email protected]
2 - 50Hertz Transmission GmbH, Berlin, Germany, [email protected],
[email protected], [email protected]
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
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.
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, [email protected], [email protected],
[email protected]
2 - SINTEF Materials & Chemistry, Trondheim, Norway, [email protected]
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
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.
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,
[email protected], [email protected],
[email protected], [email protected],
[email protected], [email protected],
[email protected], [email protected],
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.
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,
[email protected], [email protected], [email protected], [email protected]
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
Snaking of cables in empty pipes.
Paolo MAIOLI (1), Marco BACCHINI (2)
1 - Prysmian S.p.A, Milan, Italy, [email protected]
2 - Prysmian Power Link S.r.l, Milan, Italy, [email protected]
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
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.
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
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.
Lifetime pred
diction of
o an ex
xternal protectio
on of co
oldshrinkable jo
oint in EPDM
ubber su
d to therrmal age
Mouna BEN HASSINE (1), Mo
oussa NAÏT
mi ZAÏRI (2)), Xavier CO
OLIN (3),
HER (1), Gre
egory MARQ UE (1)
1 - EDF R&D, avenu
ue des Renarrdières, F-77
7818 Moret-s
sur-Loing, Fra
[email protected],
[email protected], gregory.m
[email protected]
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,
[email protected], fa
[email protected]
MR CNRS 8006,
3 - Laboratoire des Procédés
et Ingénierie
n Mécanique
e et Matériaux
x (PIMM), UM
et Mé
étiers ParisTe
ech, 151 bou
ulevard de l’H
Hôpital, F-75
5013 Paris, France,
[email protected],
The aim
m of the pressent work is
s to study th
he conseque
ences of the
ermal oxidattion on the chemical
e and mecha
anical behavior of an indu
ustrial Ethyle
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
mentary levells: First of all, the “chemiical” level tha
at calculates the alteratioon kinetics att both the
ar and macromolecular scales.
The average mo
olar mass of the elasticaally active ch
hains (i.e.
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
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
mined by coombining the
e fracture
mechaniics theory with the intrins
sic defect con
ncept (Fig.1).
DM swelling in the cyclohexane solve nt.
mechanics te
Specimen for fracture m
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
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
m network the
eory, which allows
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
e of a virtual intrinsic defe
ect which
size can
n be easily estimated,
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,
ng this appro
oach a usefu
ul tool for preedicting life time when
ng different ru
ubber compo
onents for mo
oderate to high temperature environm
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,
[email protected], [email protected]
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
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.
ding stifffness off subma
arine cables.
Paolo MA
AIOLI (1),
1 - Prysm
mian S.p.A, viale
Sarca 222,
20126 M
Milan, Italy, [email protected]
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
h cables are very large. The
T installatio
on necessitaates a precise
wledge of the mechanical parameters such as the bending stifffness, in ordeer to use app
pment and prrocedures. For
F such reassons a speciffic test equip
pment has beeen develope
ed, in
orderr to provide accurate
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
friction and allow la
ecise measuurement on a broad
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
At the e
extremities, the
sample is resting on
n two specia
al rolling supports: the ddeformation is easily
d as a beam
m and the Be
ending Stiffn
ness (BS) ca
an be computed once thhe applied force
ons are meassured.
Moving sspeed can range
from 0.01
mm/secc to 1000 mm
m/sec with maximum
defflection of 1 m at the
center, tto span a wide
range of frequenccy and bend
ding radii. The
apparatuus is very stiff,
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
To chara
acterize a ca
able, a series
s of measure
es is perform
med at consta
ant speed, w
with varying maximum
on (Figure 2),, or at consta
ant maximum
m deflection, with varying
g maximum sspeed. Each measure
es a numberr complete bending
es, because
e repetition is
s fundamentaal to pre-con
the samp
ple and to ve
erify repeatab
bility of the m
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
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.
chanicall analysis of MV
V underg
ground long lin
HTI (1), Yves
1 - EDF R&D, Ecuellles, France houssam.tan
[email protected] , yves.brum
[email protected]
2 - ERDF
F, Paris, France, roger.ta
[email protected]
he main goa
One of th
al of ERDF, French
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
d network sh
howed a certtain fragility o
or vulnerability.
For that reason, direct laying of cables
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
&D are stud
dying the po
ossibility to use
MV Undderground Long
L) for Distribu
ution Network. The use of MV Unde
erground Lon
ng Link musst reduce sig
the number of accessories and im
mprove the rreliability of th
he medium voltage
From pre
evious EDF R&D studies
s we defined
d the maxima
al cable length by taking into account security
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
mechanical forces
at term
minations and
d in accesso
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
compenssator to minimize those forces by usin
ng finite elem
Fig: Example of a MV Unde
erground Joints with expansion compensator
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, [email protected] [email protected]
2 - LS Cable & System, Gyungbuk, Korea, [email protected] [email protected]
3 - LS Cable & System, Gangwon, Korea, [email protected]
4 - Daejin University, Gyeongi, Korea, [email protected]
5 - Hoseo University, Chungnam, Korea, [email protected]
6 - Hanyang University, Gyeongi, Korea, [email protected]
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
Solutions for thefts in overhead-underground Transition
Álvaro MARCELO (1), Rafael GARCÍA (1), Maria Dolores LÓPEZ-MENCHERO (1)
1 - Red Eléctrica de España, Madrid, España,
[email protected], [email protected], [email protected]
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.
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, [email protected], [email protected], [email protected],
[email protected]
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.
AC re
ce of submarine
e cables
Paolo MA
AIOLI (1), Massimo
CHIS (1); Ga
aia DELL’ANNA (2)
1 - Prysm
mian S.p.A, Milan,
[email protected]
m, [email protected]
2 - Prysm
mian Power Link S.r.l, Milan, Italy, ga
[email protected]
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
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
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
Visible iimage
a generate
ed into the arrmouring (arm
moured cablee shown in Figure
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
the conductors.
The expe
erimental evvidence is tha
at the losses are affected
d by the way how the cabble is designe
It is also
o known thatt conductor resistance in
ncreases witth current, so
o that it is im
mportant to make
ement at the rated curren
nt and freque
ency: a test bench
has be
een developeed in order to provide
e measurement of the electrical
aracteristics of these larg
ge cables. T
The cleanness of the
power frrequency sin
ne wave has been verifie
ed and any distortion
dettected and eeliminated. The
T paper
es the effectss of presence
e of superpossed harmonics on cable resistance a nd impedanc
The leng
gth of the ca
able sample is
i important for the accuracy of the measures,
frrom one poin
nt of view
to limit sside effects and from th
he other to e
y inject the rated currennt; cable arrranged in
straight configuratio
on and witho
out close e
extraneous metallic
partts is of greeat help in reducing
nties and facilitate the operations
of removing the
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
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.
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.
Effectiveness and comparability of condition tests on MV
Peter BUYS (1), Dirk VAN HOUWELINGEN (1),
1 - Stedin BV, Rotterdam, the Netherlands, [email protected], [email protected]
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;
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, [email protected] ,
[email protected] (2), [email protected] (3), [email protected] (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
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, [email protected]
2.- BCC Cable Consulting and University of Duisburg, Germany,
[email protected]
3.- BC Hydro, Vancouver, Canada, [email protected]
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
Dear administtration, We successfu
ully submitted two ab
bstracts , No.0192 annd 0194, for Jicable 2015.
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
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
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
Daniele BONACCHI (1), Christin
LINGEN (2),, Denis LABB
BÉ (3)
1 - IMER
RYS Graphite
e & Carbon, Bodio, Switzzerland,
[email protected]
m, christine.vvanbellingen
[email protected]
2 - P&M Cable Conssulting LLC, Geneva,
Swiitzerland, dla
[email protected]
The efficciency of the
e semiconduc
ctive layer de
epends on itts electrical conductivity
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
As carbo
on black is an essentia
al constituentt of semicon
n compound
d, its quality affects the semicon
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)
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
nd, the carb
bon black agglomerates must be dis
spersed and distributed bby proper prrocessing
h only speciffically design
ned carbon b
blacks can achieve
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
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
level of
o volume ressistivity at the operating cable
tempe rature and its stability
od cable manufacturing. Proper levvel of condu
after the
ermal cycling
g is also crucial for goo
uctivity is
d only at sp
pecific carbo
on black loa
ading that is
s in turn de
ependent maainly on the
e level of
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
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
the lowe
er viscosity and the lon
nger scorch time of the compound while keepiing excellent surface
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
nt of a three-terrminal ready
HVDC in terconn
een France and
d Great Britain via the island A
y: the
Sean KE
ELLY (1), Gro
1 - Transsmission Investment, UK
K, [email protected]
2 - RTE, France, gro
[email protected]
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
Council as a part of EU’s 2030 Climate
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
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
ble generatio
on in Alderne
ey waters - the location of one of Europe’s
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
mately 220 km
m, of which around
170 kkm offshore and 50 km onshore.
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
ation of the cable
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
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
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;
an embedde
ed three term
minal functio
on with two functions in
n one single infrastructure, cross
border trade and evacua
ation of renew
wable energy
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
[1] - The Ten Years Network Development Plan published by ENTSO-E
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, [email protected],
[email protected]
2 - P&M, Geneva, Switzerland, [email protected]
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.
adsorbed water (%)
RH=60% (desorption)
max uptake (RH=95%)
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
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.
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
[email protected], [email protected], [email protected], [email protected]
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.
Results of 10 years after in
nstallation tests
s comb ined witth PD
ction on
n MV cab
Frank DE
E VRIES (1), Jacco SMIT
T (1), John V
1 - Electtrical Consulttant, Alkmaar, The Nethe
[email protected], [email protected]
2 - Senio
or Assetmanager, Arnhem
m, The Neth erlands, john
[email protected]
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).
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
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
nts as part of the after insstallation testt are:
To have insig
ght in the sta
art condition parameters of the cables
system (fingeerprint)
To have inssight in the condition o
of the cable
esystem, afte
er the volta ge withstand test is
- In situations where high testvoltagess are not pos
ssible PD tes
sts at lower ttestvoltages can be a
good alterna
ative (e.g. in
nternal brea
akdown when cable is connected
too an old sw
external flashover in case of small sizze cableboxe
- 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
primary requirement for the after installation ttest at Alliand
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
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
ables and th
he developed requireme
ents for PD behavior. Also
examplles are give
en of PD
behaviorr in relation to poor workm
manship and
d the design of accessorie
Figure 7: Foun
nd defect in 20kV
Figure 8: Related PD
D behaviour
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
1 - Prysmian Group, Delft, the Netherlands, [email protected],
[email protected], [email protected],
[email protected], [email protected]
2 - TenneT, Arnhem, the Netherlands, [email protected], [email protected]
3 - Energy Solutions (ENSOL), Delft, the Netherlands, [email protected]
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:
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
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
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
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, [email protected]
2: NEXANS Norway, Halden, NORWAY, [email protected]
3: SINTEF Energy, Trondheim, NORWAY, [email protected], [email protected]
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,
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,
[email protected], [email protected], [email protected]
2 - ESPCI, SIMM, Paris, France, [email protected]
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.
Efficient project management of high voltage underground
cable systems against self-evident facts
1 - RTE, Paris, France, [email protected], [email protected]
 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
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.
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, [email protected],
[email protected], [email protected]
2 - ORES, Louvain-la-Neuve, Belgium, [email protected]
3 - CERISIC, Mons, Belgium, [email protected], [email protected]
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
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.
Rejuvenation of EPR-insulated medium voltage underground cables
Richard VARJIAN (1), David BUSBY (1), Glen BERTINI (1)
1 - Novinium, Inc, Auburn, Washington, USA, [email protected] ,
[email protected] , [email protected]
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
 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.
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).
Resilient 12 to 36kV
V touch safe aerial netw
work so
olution with
petitive Total
ost of O
Lars EFR
GMAN, Johan
1 - nkt ca
ables AB, Fa
alun; Sweden
n, email: [email protected],
[email protected], johan.ahma
[email protected]
This sysstem has be
een develop
ped in respo
onse to utiliities demand
ds for moree efficient in
methodss, cost savin
ngs and inc
creased relia
ability. The fully insulatted aerial caables offers
s a more
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
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
wer to mines
s through verrtical drilled hholes.
e as aerial an
nd ground ca
Fig 2 Use
Fig 3 Joint installation
Fig 4 Steep rise
Fig 5-6 C
Cable from air into a subsstation
Fig 7 Trees on ccable after sttorm
The overrall project execution
mes are shortter and more
e cost effective. This incluudes all phases, from
concession, planning
g, layout an
nd design, aand finally during
building of the innsulated aerrial cable
ple: a cost effective
wayy to upgrade an existing transmissionn line is to install the
An illustrrative examp
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
new line
e is conseqquently not required.
After rem
moval of the old conducto
ors, the fullyy insulated ca
able can be elevated
live on line.
In otherr applicationss fully insula
ated aerial caables have been
built in
n parallel witth the LV lin
nes which
needed u
upgrading du
ue to overloa
ad or voltagee drop issuess.
g the electriical grid with fully insul ated aerial cables provides a lowerr TCO (Total Cost of
hip) than air insulated ba
are lines. Th
he improved service - no
o loss of suppply for custtomers in
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
g waves and
d vibration arre no issues ffor these cab
ble lines as documented
nology on
by EA-Techn
their She
etland Island
d test site.
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
[email protected], [email protected], [email protected], [email protected]
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
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
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
Validation of a generic tool of kinetic simulation of cable
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, [email protected], [email protected]
, [email protected]
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.
[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,
[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.
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,
[email protected]
2 - Electric Power Research Institute, Charlotte, USA,
[email protected]
3 - Cable Consulting International Ltd, Sevenoaks, UK,
[email protected], [email protected]
4 - Dassault Systemes UK Ltd, Sevenoaks, UK, [email protected]
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.
Key properties of next generation XLPE insulation material
for HVDC cables
1 - Borealis AB, Stenungsund, Sweden,
[email protected], [email protected],
[email protected], [email protected],
[email protected], [email protected],
[email protected]
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.
Development of a 345kV XLPE extruded cable for HVDC
Marie-Laure PAUPARDIN (1), Mohamed MAMMERI (1)
1 - GENERAL CABLE, Montereau France, [email protected],
[email protected]
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
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
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, [email protected],
[email protected], [email protected],
2 - Albert-Ludwigs-Universität, Freiburg, Germany, [email protected] .
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.
Identification of cable local thermal stress with time domain
Thierry ESPILIT (1), Jean Marie FAGEON (2), Sandrine FRANCOIS (3)
1 - EDF R&D, Moret sur Loing, France, [email protected],
2 - EDF DPN, Paris, France, [email protected]
3 - EDF SEPTEN, Lyon, France, [email protected]
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
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.
High safety
y and low m
ance ae
erial ca
able sy
g extrem
me weath
Lars EFR
1 - nkt ca
ables AB, Fa
alun; Sweden
n, email: [email protected],
[email protected], [email protected]
om, [email protected]
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
es. And it will be expensiv
ve for the enntire commun
In 2012, the costs we
ere estimated at nearly 1 billion SEK almost 100 million
Euro - in Sweden alone.
A system has been
n developed
d in respon se to utilitie
es demands
s to withstannd extreme weather
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
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
Fig 1 Snow
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
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 as sand, ssalt and cond
ducting dustt (may causee fires). Con
bare line
e systems arre prone to short
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
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,
g of lines can be performe
ed during norrmal working
g hours.
Fig 2 Heavy
tree on live cable
Fig 3 Trees on livee cable afterr storm
Transient thermal phenomenon in HVDC extruded cables
under test and operating condition - numerical simulation and
Christian FROHNE (1), Johan KARLSTRAND (2), Marie-Helene LUTON (3),
1 - Nexans Deutschland GmbH, Hannover, Germany, [email protected]
2 - JK Cablegrid Consulting AB, Karlskrona, Sweden, [email protected]
3 - Nexans France, Calais, France, [email protected]
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.
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,
[email protected], [email protected], [email protected]
2 - EDF R&D, Moret sur Loing, France, [email protected]
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.
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, [email protected]
2 - IREQ, Varennes, Canada, [email protected]
3 - SINTEF Energy Research, Norway, [email protected],
4 - ERDF, Paris La Défense, France, [email protected]
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
Copper-clad aluminum as an alternative to copper flexible
conductors for electric power cables: opportunities and
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. [email protected],
[email protected], [email protected],
[email protected],
2 - Prysmian Cavi e Sistemi Italia SRL, Milan, ITALY. [email protected]
3 - Dynext SRL, Legnano (Milan), ITALY. [email protected], [email protected]
4 - G.B. Studio, Milan, ITALY. [email protected]
5 - Copperweld, Nashville, Tennessee, USA. [email protected], [email protected]
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.
Polyethylene Cables using Inorganic Filler.
Sherif ESSAWI (1), Loai NASRAT (2), Jeanette ASSAD (3), Mahmoud MOSTAFA (4)
1 : Electrical Power Dept. ,Petrojet , Cairo, Egypt,[email protected]
2 : Electrical Power and Machines Eng. Dept, Aswan University, Aswan, Egypt, [email protected]
3 : Polymers and Pigments Dept., National Research Center, Cairo,Egypt, [email protected]
4 : Electrical Power and Machines Eng. Dept, Ain Shams University, Cairo, Egypt,
[email protected]
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
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
Key words
XLPE cables; inorganic filler; dielectric strength; TGA; electrical and thermal properties.
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, [email protected]
2 - Terna Italia, Rome, Italy, [email protected]
3 - University of Bologna, Bologna, Italy, [email protected]
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.
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.
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.
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.
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.
Fig. 1: TDR Trace of a lo
ong HVDC su
ubmarine cable: SA.CO.II, Italy to Corrsica, 105 km
DGA (Dissolved Gas Analysis) diagnostic method reveals
internal carbonization in oil-filled high voltage extruded cable
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,
[email protected], [email protected], [email protected]
2 - Lincoln Electric System, Lincoln, US,
[email protected], [email protected],
3 - G&W Electric Company, Bolingbrook, US,
[email protected]
4 - EPRI, Charlotte, US,
[email protected], [email protected]
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.
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, [email protected],
[email protected], [email protected]
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
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
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.
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,
b[email protected], [email protected]
2 - TU Darmstadt, Geothermal Science and Technology, Darmstadt, Germany,
[email protected], [email protected], [email protected]
3 - Bayernwerk / e-on, Regensburg, [email protected]
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
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.
Cable constraints due to background harmonic amplifications
Yannick FILLION (1), Simon DESCHANVRES (1), Nathalie BOUDINET (1)
1 - RTE, Paris, France,
[email protected], [email protected],
[email protected]
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
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.
V Cable Systtem Qu
ualification to IEC 6
011 /
A S-108-7
720-2012 / AE
S-9-06 / IEEE
E 48-20
009 /
IEEE 404-201
Ravi GA
ANATRA (1), Joshua PER
RKEL (2), M ilan UZELEC
C (3), Jose ZAMUDIO
Wire and Cab
ble, Suwanee, USA rgan
[email protected]
RAC, Atlanta
a, USA joshu
[email protected]
3 G&W E
Electric, Chiccago, USA [email protected]
4 Viakab
ble, Monterre
ey, Mexico JZ
[email protected]
on of confo
ormance req
quirements ffrom multiple standards
s remains aakin to a high
ance. Users express a prreference forr the cable sy
ystem route via IEC / AE IC, whilst rec
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
The paper will discusss:
design of the
test loo
op including
g the optim
sselection of the
t compone
ents (Fig 1),
ssequencing of
o construction and the re
equired tests
sselection of the most strringent elem ents (voltage
number of cycles, te
emperaturess) within the
rrespective sttandards,
outcome of the
t program and
cconsiderations for technical committe
ees engaged
d in
tthe develo
opment and
d maintena
ance of the
ned specifica
Fig.1 Optimized
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
Fig 2 IEC on
Fig 3 IEEE only
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
and critical limittations of IEE
EE 48 and IEEE 404 reqquirements that
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.
Reliability of Cable Based Transmission Grids Operated
Based on Temperature Limits
Rasmus OLSEN (1), Joachim HOLBOELL (2), Unnur Stella GUDMUNDSDOTTIR (3)
1 -, Fredericia, Denmark, [email protected]
2 - Technical University of Denmark, Kgs. Lyngby, Denmark, [email protected]
3 - Dong Energy, Fredericia, Denmark, [email protected]
The Danish transmission system operator (TSO),, 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 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.
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 -, Fredericia, Denmark, [email protected] , [email protected]
2 - Technical University of Denmark, Kgs. Lyngby, Denmark, [email protected]
3 - Dong Energy, Fredericia, Denmark, [email protected]
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)
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.
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, [email protected], [email protected]
2 - IPH Berlin, Berlin, Germany, [email protected], [email protected]
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.
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,
[email protected], [email protected], [email protected]
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.
Cable system
m test setup showing con
Fig. 1: C
cable piece and te
elemetry systtem installatiion
ystem test seetup showing
g control
Fig. 2: Cable sy
cable and fiber-o
optic tempera
rature monito
oring and
contrrol system innstallation
ctiveness of te
ests affter ins
n on p
power cable
Peter VA
ELEN (1), Be
ernd VAN MA
AANEN (1), Fred
1 - DNV GL, Arnhem
m, The Netherlands,
[email protected]
[email protected]
2 - Eindh
hoven University of Technology, Eind
dhoven, The Netherlands
[email protected]
Due to tthe increasin
ng demand for power, the expansion of geogrraphical needd for powerr and the
ment of old circuits, the amount of new cable installations
is increasin g rapidly arround the
Despite various testt programs in combinattion with oth
her quality assurance
annd control programs,
failures can never completely
b avoided. From failure
e investigations, togetheer with statis
stics and
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
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
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.
ds describe many tests during cable
e and access
sory design and producttion (pre-qua
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
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
in the sttandards tha
at should dettect imperfecctions introdu
uced during installations (and transp
Various technologiess exist (50 Hz,
H Series-Re
esonance, VLF,
d AC, Cosin us Rectangu
ular, etc.)
which ccan additionally be com
mbined with detection of partial discharges ( PDs) and tan
ement. Experience with one
o technolo
ogy is broade
er and more excepted thaan with the other,
the actual effectiveness of these
e techniquess is not really
y known, especially of thhe newer tec
These n
newer techniq
ques are try
ying to gain m
market share
e, and could
d be interestting from eco
practicall or technology point of view,
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
ement examp
ples here an
nd there. Larrger scale la
aboratory experiments arre almost ex
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
will inve
estigate the
eness of the various me
entioned tec hniques in
an indep
pendent wayy. To obtain unquestionab
ble results,
dency is obta
ained by invo
olving netwo
ork owners,
cable ma
anufactures, accessory manufactures
s and DNV
GL. Furtthermore, the planned in
nvestigation involves a
setup wiith a large amount
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
ally proven re
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, [email protected], [email protected],
[email protected]
2 - Nexans, France, [email protected], [email protected]
3 - General Cable, France,
[email protected], [email protected]
4 - SYCABEL, France, [email protected]
5 - RTE, France, [email protected]
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
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
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
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.
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, [email protected]
2 - Nexans Norway AS, Halden, Norway, [email protected]
3 - BOREALIS AB, Stenungsund, Sweden,
[email protected], [email protected]
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
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.
Dielectric strength of γ-radiation cross-linked, high vinylcontent polyethylene
C. MÜLLER (1)*, M.R. ANDERSSON (1),(4)*
1 - Department of Chemical and Biological Engineering/Polymer Technology, Chalmers University of
Technology, 41296, Göteborg, Sweden, [email protected], [email protected],
2 - Department of Materials and Manufacturing Technology/High Voltage Engineering, Chalmers
University of Technology, 41296, Göteborg, Sweden, [email protected],
[email protected]
3 - Department of Chemical and Biological Engineering/Nuclear Chemistry, Chalmers University of
Technology, 41296, Göteborg, Sweden, [email protected]
4 - Ian Wark Research Institute, University of South Australia, Mawson Lakes, South Australia 5095,
Australia, [email protected]
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
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, [email protected]
2 - Prysmian Group, France, [email protected],
[email protected] , [email protected]
3 - General Cable,France, [email protected],
[email protected]
4- SYCABEL, France, [email protected]
5 - RTE, France, [email protected]
6 - GIMELEC, France, [email protected]
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.
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, [email protected] , [email protected]
2 - Dow Chemical (China) Investment Co. Ltd., Shanghai, China, [email protected]
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.
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, [email protected]
2 - The Dow Chemical Company, Collegeville, USA, [email protected]
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.
Belgian exp
e with real tim
me temperature
e syste
em in
n with distribute
ed temperature sensing
g techniques
Pieter LE
EY, Patrick M
Jean--Pierre FALC
H (1),
1 - Elia, Brussels, Be
[email protected], [email protected], [email protected];
[email protected]; je
ean-pierre.fa [email protected]
In the latte 90’s, the Belgian
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
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
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
wind ene
ergy producttion. The loa
ad situation in the grid is changing rapidly from a unidirectional to a
onal networkk. At this mo
oment there is a need frrom operatio
ons side to uuse a perma
anent real
time thermal rating (RTTR)
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
e monitoring
g system
All new HV cable circuits startin
ng from 110kkV are equip
pped with
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
systems, due to th
he higher accuracy
nd the lowe
er spatial
on. The SM fibres
are us
sed for longe
er ranges, where
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.
Figure 1: HV caable 110kV with integrated
Dynamiic Line Ratin
The first fixed RTTR monitoring system
will b
be installed in
n the 33 km link 150kV K
Koksijde-Slijkens (type
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
farms a
and increasin
ng loads with future connnection of Belwind
and Nortthwind. The data of the DTS
is transfferred over the
t SCADA network
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
ent condition
ns, maximum
m overload capacity forr a given time, maximuum time forr a given
d,.. With the technique of
o RTTR Elia
a has the op
pportunity to
o follow up tthe load of the
system in real time and
a have an idea of the m
maximum ins
stant load and
d the overloaad capabilitie
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
pability of the
e 150kV link of Koksijde--Slijkens by using an
RTTR syystem.
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, [email protected] ,
[email protected] , [email protected] , [email protected]
2 - Zhongtian Technology Group Co., Ltd, Nantong, China, [email protected]
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.
Transients on DC cables connected to VSC converters
Sébastien DENNETIERE (1), Hani SAAD (1), Pierre HONDAA (1), Antoine NAUD (1)
1 - RTE, Paris, France, [email protected] - 001 514 912 0420,
[email protected], [email protected], [email protected]
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.
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), [email protected]
2 - Grupo General Cable Sistemas, S.A. GCC Manlleu, Spain, [email protected]
3 - Chevron Energy Technology Company, Houston, TX, 77002 (USA),
[email protected], [email protected]
4 - Aker Solutions, Mobile, AL 36605, (USA), [email protected]
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
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,
[email protected], [email protected], [email protected], [email protected]
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.
The charactteristics
s of rec
e therm
mo-plastiic base
ed on
e blends
s for exttruded cables
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,
[email protected]
n, [email protected], flowerlm
[email protected],
[email protected]
2 - Electtric Power Re
esearch Instiitute of China
a Southern Grid,
[email protected]
n, [email protected]
Due to tthe poor recyyclability and
d high energ
gy consumpttion of XLPE
E, it is very aacute to develop new
dly insulation
n materials. T
The binary polyethylene
e blend HDP
h been
considerred as one of the poten
ntial non-cro
osslinked environmental--friendly insuulation materials with
able electrica
al and mecha
anical perform
In this in
nvestigation, the propertties of binarry polyethyle
ene blend sy
ystems whichh contain HDPE and
have been measured
d discussed.. The blends are blending
g by torque rrheometer in
n different
ons. Tensile and electric
cal tests havve been take
en on these blends with different pro
From the
e results, a blend
m which has tthe most exc
cellent comp
prehensive peerformance has been
chosen: 70%wt LLDPE-30%wt HDPE
(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
1015 Ω·m
probabiliity). It is also
o pretended that crystalllinity of the blends
increase and am orphous is dispersed
evenly in crystalline phase by taking diifferential sc
canning calorimetry(DSC
C) and mic
observattion after co
orroding in boiling
ptanes, there
efor the blends have suuperior perfo
more, water-ttreeing test of the chossen blend sh
hows that the chosen m
material can suppress
eeing. In summary, the recyclable thermo-plastic blends have
great ppotential in using for
on of green insulation
d cables and can develop
p new directio
aterials for poower cables.
nostics of conttrol and instrum
on cable
es in nu
er plantt via tim
me-freq uency domain reflecttometry
y with
mal referrence siignal
won LEE (1),, Seung-Jin CHANG
(1), Moon-Kang JUNG (1), Yee-Jin
N (1), Geon-S
HIN (1)
LEE (1), Jin Bae PARK (1), Yong-June
1 - Yonssei Universityy, Seoul, Rep
public of Kore
[email protected] , [email protected] , moonrive
[email protected] , hanyj
[email protected] ,
[email protected] , jb
[email protected] , yon
[email protected]
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
ation which aare considere
ed one of
the mostt crucial com
mponents in nuclear
er plant’s saffety. Moreove
er, the C&I ccables are ex
xposed to
severe e
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
n, estimating
g its remaining life, and locating deffects before the failure ooccurs is req
quired for
safe ope
eration of nucclear power plant
operati on.
Among vvarieties of cable
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
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
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
omain simulta
aneously. Th
he last graph
h shows timee-frequency the cross
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;
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,
method to sett parameters
s requires ne
etwork analyz
zer to determ
mine the freqquency chara
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.
ore, it is neceessary to develop the
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
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,
[email protected] , [email protected] , [email protected] , [email protected] ,
[email protected] , [email protected], [email protected]
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.
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.
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,
[email protected] , [email protected]
2 - School of Electrical Engineering and Informatics - Bandung Institute of Technology, Bandung,
Indonesia, [email protected]
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.
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,
[email protected] , [email protected]
2 - School of Electrical Engineering and Informatics - Bandung Institute of Technology, Bandung,
Indonesia, [email protected]
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.
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, [email protected]
2 - Rheinische Netzgesellschaft, Cologne, Germany, [email protected]
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
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.
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
[email protected], [email protected], [email protected]
2 - Electric Power Research Institute of China Southern Grid
[email protected], [email protected]
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.
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.
[email protected], [email protected], [email protected],
[email protected]
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
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.
Withdrawn by the author, in order to participate to the YRC Contest
Space charge density (C/m3)
Space charge density (C/m3)
Thickness (um)
Thickness (um)
(a) 0 phr ZnO,
Space charge density (C/m3)
Thickness (um)
Thickness (um)
(c) 1 phr ZnO
(d) 3 phr ZnO
Space charge density (C/m3)
Space charge density (C/m3)
(b) 0.5 phr ZnO
Thickness (um)
(e) 5phr ZnO
Fig. 1:Space charge distributions under a DC field of 30kV/mm.
Improvements on dry type design for GIS and transformer
termination up to 300kV, by means of adjustable compression
Oldrich SEKULA (1), Dr. Guoyan SUN (1),
1 - Brugg Kabel AG, Klosterzelgstrasse 28, 5200 Brugg, Switzerland,
[email protected], [email protected] ,
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
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.
Gravitational cooling of cable installations
Heinrich BRAKELMANN (1), Volker WASCHK (2)
1 - BCC Cable Consulting, Rheinberg, Germany, [email protected]
2 - nkt cables, Cologne, Germany, [email protected]
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.
Fig. 1:
Thermal bottleneck over 50 m with
steam pipe in a depth of 2.0 m and a
cable double-system
heat dissipating
2500 mm2 RMS;
I = 3467 A; m = 0,80
cable double-system
in a duct
with great laying
heat absorbing
below: cooling facilities (schematic)
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,
[email protected], [email protected], [email protected]
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.
Assessment of environmental impact of submarine cables
and offshore connections
Damien SAFFROY, Frédéric LESUR, Aurore RAOUX
1 - RTE, Paris, France,
[email protected], [email protected]
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
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.
Electro-Thermal Analysis of Low and Medium Voltage Cable
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, 3150 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)
Analytical Method
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
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
Temperture (Degrees Celsius)
& X= 0.0625 m
& X= 0.125 m
& X= 0.25 m
& X= 0.45 m
Distance from the center of the joint (m)
Fig. 2 Conductor temperature profiles at fixed connector thickness (2t=4 mm) and various lengths of
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.
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,
[email protected]
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.
French feedback on civil and installation
transmission underground cable systems
Hervé GUYOT (1), Serge HASCOET, Frédéric LESUR (2)
1 - SERCE, Paris, France,
[email protected]
2 - RTE, Paris, France,
[email protected], [email protected]
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.
Measurements of losses on three core submarine power
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, [email protected], [email protected]
2 - nkt cables group gmbh & KG, Germany, [email protected]
3 - EDF-CIST, Saint-Denis, France, [email protected]
4 - RTE, Paris La Défense, France, [email protected]
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.
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
[email protected], [email protected], [email protected],
[email protected], [email protected]
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.
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.
[email protected]
2 - Institut Teknologi Bandung, Jalan Ganesha 10, Bandung, Indonesia.
[email protected]
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
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, [email protected], [email protected]
2 - Lodz University of Technology, Poland, [email protected]
3 - EDF CIST, Dubai, [email protected]
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
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
oved de
esign for
antii-scatterring in fault c
on of
oor term
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.
[email protected], you
[email protected], [email protected],
[email protected]
V cable system became
e close to o
our environm
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or termination is particullarly expose
ed to the ou
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surges, sshort-circuit current is ca
aused. It makkes internal arcs
and hea
avy inner preessure inevita
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e, broken pieces fly awayy near the terrmination and
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Many ou
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This issue is
s already a problem
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damage led by
b Europe ele
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We designed a new type of outd
door terminattion for prote
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secondaary damage. Although
wn of outdo
oor terminattion occurs,, the new design
ure anti-scatttering. In 2012,
ed anti-scatttering test(internal arc te
est) in CESI Italy according to HD6322 S2(2008) standard.
We teste
ed on outdo
oor terminations for volttage grades
s of 170kV and
245kV. The tests simulated
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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.
Online PD monitoring of short cable systems installed in
Fernando GARNACHO (1), Javier ORTEGO (2), Miguel Ángel SÁNCHEZ-URÁN (2), Alberto
1 - LCOE-FFII, Madrid, Spain, [email protected]
2 - ETSIDI-UPM, Madrid, Spain, [email protected] , [email protected]
3 - UFD-Gas Natural Fenosa, Madrid, Spain, [email protected]
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.
bstation HV
V / MV
MV Cable system
HV Cable system
ntrol & Analysis
Meaasuring System
PD Sensor
g. 1: Online PD monitorin
ng system installed in pow
wer substatioon.
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,
[email protected], [email protected],
[email protected]
2 - EDF R&D, Les Renardières, Ecuelles, France,
[email protected], [email protected]
3 - RTE, Paris La Défense, France,
[email protected], [email protected]
4 - BOREALIS, Stenungsund, Sweden, [email protected],
[email protected], [email protected]
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.
Compact paperless joint for transition from LPFF to XLPE
Pietro CORSARO (1)
1 - Brugg Kabel AG, Brugg, Switzerland, [email protected]
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
Performance evaluation of integrity monitoring based on
optical fibre distributed temperature and distributed acoustic
Chris CONWAY (1), Michael MONDANOS (2)
1 : Bandweaver, 30 Magnolia Court, West Hall Road, Richmond, UK, TW9 4EQ.
[email protected]
2 : Silixa Ltd., Silixa House, 230 Centennial Park, Centennial Avenue, Elstree, UK, WD6 3SN.
[email protected]
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
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.
Feedback on the management of transmission lines magnetic
fields in France
Matthieu CABAU, Frédéric LESUR, Francois DESCHAMPS
1 - RTE, Paris, France
[email protected], [email protected],
[email protected]
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 ( 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.
Calculation of the current
arrangement in a deep tunnel
George ANDERS (1), Boguslaw BOCHENSKI (2), Gunnar HENNING (3)
1.- Lodz University of Technology, Lodz, Poland, [email protected]
2.- Kinectrics Inc., Toronto, Canada, [email protected]
3. - ABB HV Cables, Karlskrona, Sweden, [email protected]
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.
Fig. 2
Model of a fragment of the cable tunnel
The equation for heat balance in the tunnel is:
Wo  dz 
 ( z )     o
 dz 
 c pa  v   
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.
Derating factors for multiple circuits of low and medium
voltage cable installations
Boguslaw BOCHENSKI (1), George J. ANDERS (2)
1 - Kinectrics Inc., Toronto, Canada; [email protected]
2 - Lodz University of Technology, Lodz, Poland; [email protected]
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.
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), [email protected],
2 - Poznan University of Technology, Poznan, (Poland), [email protected]
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
Screen on the
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.
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.
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, [email protected]
2 - Endesa Distribución Eléctrica, Palma de Mallorca, Spain,
[email protected], [email protected], [email protected]
3 - MARTIN BAUR S.A., Barcelona, Spain, [email protected]
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.
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,
[email protected], [email protected], [email protected]
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
Key words
Insulation, Dielectric, Water tree, VLF tan delta, TDS, Breakdown voltage, Weibull.
Use o
of confo
ormal trransform
m for cu
urrent ra
ating ca
ons of
d cable systems
Frédéric LESUR,
1 - RTE, Paris, Francce, frederic.le
[email protected]
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
being assumed con
nstant). Formulae are applicable for
cables buried
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
(e.g. F
Finite Element Method), with
w an increeased complexity.
Thirty ye
ears ago, Cigré
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
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
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
The upp
per and lowe
er sides repre
esent the gro
ound and ca
able surfaces
s respectivel y. In the tran
plane, issotherms beccome lines parallel
to the
e line repres
senting the ground
surfacce, and flux lines are
nted by lines perpendicular to the isottherms.
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).
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
[email protected]
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.
Condition monitoring of electrical
Resonance Analysis (LIRA).
Paolo F. FANTONI (1)
1 - Wirescan AS,kVeldroveien 7, NO-1407 Vinterbro, Norway, [email protected]
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.
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,
[email protected], [email protected], [email protected]
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.
Measures to reduce skin-effect losses in power cables with
optimized conductor design and their evaluation by
Gero SCHRÖDER (1), Volker WASCHK (2), Ronald PLATH (3), Rolf SCHUHMANN (3),
1 - Südkabel GmbH, Mannheim, Germany, [email protected]
2 - NKT Cables GmbH & Co. KG, Köln, Germany, [email protected]
3 - Technical University of Berlin, Berlin, Germany,
[email protected], [email protected], [email protected]
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
[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,
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,
[email protected], [email protected],
2 - North China Electric Power Research Institute Co, Ltd, Beijing 100045, China
[email protected] .
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
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,
[email protected] , [email protected], [email protected]
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.
Final Countd
down fo
or CPR Cable Classific
cation - View frrom a
Notifiied Bod
1 - VDE Testing and Certification
n Institute, Offfenbach, Ge
ermany, chris
[email protected]
In July 2
2013, the ne
ew European
n Constructio
on Products Regulation 305/2011
(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
the proce
ess of conformity assess
sment and th
he demands on internal production
asssessment, but
b also a
lot of otther aspectss like the assignment
of each fire class with the approppriate test sttandards.
more, in 201
14, CEN iss
sued the EN
N 13501-6 standard,
escribing thrreshold values to be
reached in the differe
ent tests for obtaining
a ccertain fire class.
eless, at the end of 2014,, the publicattion (and therrefore harmo
onization) of tthese standards in the
Official Journal of the European Union
has nott taken place,, but is expec
cted to happeen in 2015. Before
on, the CPR
R cannot be applied forr cables, me
eaning that the
different obligations on cable
manufaccturers like providing
a Declaration
of Performance (DoP) an
nd therefor aapplying a System
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
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.
Fig. 1: Systems off Assessmen
n of Constan
ncy of Perform
The oblig
gations on th
he Notified Bodies
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
to be co
considered fo
or testing,
on and certification. On the other h
hand, Notifie
ed Bodies have to be im
mpartial, neutral and
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
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.
The main part w
will relate to the above
ed detail aspects during
g testing, insspection and
d certification
n, including some input from the
WG10, the relevant workin
ng group for cables within
n the Group of Notified B
Bodies. It will cover for
e information concerning
f power an
nd communiccation cables
EXAP rules for
Use of manu
ufacturer’s te
est facilities
Process of conformity
Rules for con
ntinuous surv
veillance / fa
actory inspec