Guide to Power Transformer Specification Issues www.epecentre.ac.nz Electric Power Engineering Centre – Guide to Power Transformer Specification Issues Edition 2, January 2009 DISCLAIMER This document was prepared by the Electric Power Engineering Centre (EPECentre) at the University of Canterbury in Christchurch, New Zealand. The content included in this document is based on a power transformer specification workshop held in July 2007. The EPECentre takes no responsibility for damages or other liability whatsoever from the use of this document. This includes any consequential damages resulting from interpretation of material. Electric Power Engineering Centre, University of Canterbury Published by Electric Power Engineering Centre (EPECentre), University of Canterbury 1st Edition 1, August 2007 [revised January 2008] Reviewed & edited by: Wade G. Enright BE(Hons), PhD, MIPENZ, MCIGRE Produced & co-edited by: Joseph D. Lawrence BE, MEM, PMP, MPMINZ, MNZIM Acknowledgements: Sponsors and participants of the EPECentre Power Transformer Conference 2007, Workshop: Guide to Transformer Technical Specification, 3 July 2007, University of Canterbury, Christchurch, New Zealand Electric Power Engineering Centre University of Canterbury Private Bag 4800 Christchurch New Zealand T: +64 3 366 7001 E: info@epecentre.ac.nz www.epecentre.ac.nz © 2008 Electric Power Engineering Centre, University of Canterbury, Christchurch, New Zealand. All rights reserved, no part of this publication may be reproduced or circulated without written permission from the Publisher. 1 Electric Power Engineering Centre – Guide to Power Transformer Specification Issues Edition 2, January 2009 Electric Power Engineering Centre - GUIDE TO POWER TRANSFORMER SPECIFICATION ISSUES CONTENTS FOREWORD ...................................................................................................................................3 INTRODUCTION .............................................................................................................................4 SETTING THE SCENE....................................................................................................................6 PART 1. FIRE & EXPLOSION PROTECTION ................................................................................7 PART 2.THE DETAILED DESIGN REVIEW ...................................................................................9 PART 3. TECHNICAL SPECIFICATION EXPERIENCES ............................................................11 APPENDIX A. REFURBISHMENT & REPAIR OF POWER TRANSFORMERS*…………………13 APPENDIX B. DRIVEN FACTORS FOR TRANSFORMER LONG LIFE** ………………………..30 APPENDIX C. EPECENTRE ELECTRIC POWER R&D CAPABILITY ......………………………..92 * Courtesy of Transfield Services Limited © ** Courtesy of Pauwels Trafo Asia Limited © 2 Electric Power Engineering Centre – Guide to Power Transformer Specification Issues Edition 2, January 2009 FOREWORD Tēnᾱ koutou te whᾱnau, Nga mihi ki koutou mana, koutou korero, koutou whakaaro, koutou awhina. Kua mutu te wᾱnanga. No reira tēnᾱ koutou, tēnᾱ koutou, tēnᾱ koutou katoa. The power transformer technical specification workshop is completed. Thank you to all that attended, for your presence, discussions, thoughts and support. Australasia is currently most active in the processes associated with purchasing power transformers. July 2007 was a good time to peer review some important components within this process, and some of the present practices. It was also fantastic to have representatives from Indonesia, France, Australia and Aotearoa involved in the workshop. The Electric Power Engineering Centre (EPECentre) has prepared a summary of the workshop for each of you, enjoy. Hei kōna, Dr. Wade Enright and Prof. Pat Bodger (EPECentre Director) pictured with the 15kVA, single phase, prototype superconducting transformer, designed and built at the University of Canterbury in Christchurch, New Zealand. Wade Enright Dr. Wade G. Enright Associate, Electric Power Engineering Centre, University of Canterbury August 2007 3 Electric Power Engineering Centre – Guide to Power Transformer Specification Issues Edition 2, January 2009 INTRODUCTION Power Transformer Technical Specification During 2006 and 2007 to date, an unusually high number of requests have arrived for Technical Specification reviews, both in New Zealand and Australia. More than six power transformer Technical Specifications for machines over 200MVA in New Zealand alone. The challenges of a significantly loaded electrical network reliant on service aged equipment: refurbish and/or replace. The challenges of increasing load and “new” generation types e.g. wind turbines. The commodity price issues (copper, electrical steel, structural steel and oil). The changes from well established European factories to new South East Asian manufacturing sites. The need for form relationships with new people (new manufacturer personnel, new employers/clients). It may be that power transformer Technical Specifications has become cumbersome, out of focus and needs a “spring clean”. The peer review process: are our ideas good ones? Published Documents Published documents that contain guidelines specific to power transformer Technical Specification: CIGRE Working Group 12.15., “Guide for Customers Specifications for Transformers 100MVA and 123kV and above”, Technical Brochure 156, April 2000. ABB, “Transformer Handbook”, ABB Power Technologies Management Ltd, 2004. Heathcote, M.J., “The J&P Transformer Book”, Twelfth Edition, Newnes, 1998, ISBN 07506 1158 8. ABB, “Testing of Power Transformers, Routine Tests, Type Tests and Special Tests”, 1st Edition, ABB Business Area Power Transformers, 2003, ISBN 3 00 010400 3. 4 Electric Power Engineering Centre – Guide to Power Transformer Specification Issues Edition 2, January 2009 Refocus: Why Have a Technical Specification? From an Employer (Client) perspective: To formally and fairly communicate exactly what you want the Contractor to deliver. From a Contractor perspective: To be able to accurately offer services and products which provide a satisfactory solution (technical/commercial) to an Employer (Client); while remaining a long-term profitable business. For both Contractors and Employers (Clients): To avoid relationship mishaps associated with costly Variation work misunderstandings. 5 Electric Power Engineering Centre – Guide to Power Transformer Specification Issues SETTING THE SCENE Edition 2, January 2009 The repair bill is significant. What is the Industry going to do about it? 1. The Use of International Standards – Example: Australian Standards AS60076.1-2005: “Power Transformers – General.” AS2374.2-1997: “Power Transformers – Temperature rise.” AS2374.3.0 – 1982 “Power Transformers – Insulation levels and dielectric tests, General Requirements.” Including Amendment 1 – 1992. AS2374.3.1 – 1992 “Power Transformers – Insulation levels and dielectric tests, external clearances in air.” AS60076.4 – 2006 “Power Transformers – Guide to the lightning impulse and switching impulse testing – power transformers and reactors.” 3. Partial Discharge Testing of Refurbished Power Transformers in New Zealand This is an expensive and time consuming test. It could commonly be the case that the original power transformers were not designed to be subjected to the Partial Discharge test. Why are expected Partial Discharge pass levels being set at 50% of the value specified in the IEC International Standard for new transformers? What is the plan if the Partial Discharge fails? The Partial Discharge test initially failed but has now passed, how does this make you feel? AS2374.5 - 1982 “Power Transformers – Ability to withstand short-circuit.” AS2374.6 - 1994 “Power Transformers – Determination of transformer and reactor sound levels.” Including Amendment 1 – 2000. AS2374.7-1997 “Power Transformers – Loading guide for oil immersed power transformers.” Including Amendment 1 – 1998. AS2374.8 – 2000 “Power Transformers – Application Guide.” AS1265 – 1990: “Bushings for alternating voltages above 1000V.” AS60214.1 – 2005: “Tap-changers, Performance requirements and test methods.” AS60214.2 – 2006 “Tap-changers, Application guide.” 4. On-Load Tap-Changers on Generator Step-Up Transformers More and more tapping ranges. Lower and lower tap sizes. Why – the generator has an Automatic Voltage Regulator? Has system simulation taken over the importance of reliable machine design? What is the impact upon short-circuit with-stand e.g. multi-start, layer wound tapping windings? 5. Transformer Cooling ONAN/ONAF/ODAF versus ODW versus ONAN? 2. The Single-Point Earthing of Power Transformer Cores, Frames and Tanks The insulation is failing. Dissolved Gas Analysis tests are being over-run with alarming gas signatures. When should we buy straight ONAN machines? Reliable, not dependent on l.v. systems, and simple. ONAN/ODAF may be significantly more cost effective above 65MVA? Will specifying ODW significantly reduce the number of Contractors who will tender for the work? 6 Electric Power Engineering Centre – Guide to Power Transformer Specification Issues Edition 2, January 2009 steam and gas plant than hydro. All money and susceptible to damage. Nitrogen. Enclosure. Fire Wall. Blast walls in all critical areas. Design of location. Fast acting protection. PART 1. FIRE & EXPLOSION PROTECTION What is considered an acceptable level of fire and explosion protection that should be specified for power transformers in the c) A generator step-up transformer connected to a following scenarios? hydro-turbine unit Environmental risks - oil contamination of lakes / rivers, etc. Containment of full volume of oil. Buchholz relay. Pressure relief. Vented cable box. Generator circuit breaker. Bushing monitoring. Conservator tank isolation. Choice of oil. Temperature indicators. Fire protection (foam). GSU transformer - generator CB – required. Water sprinklers and oil interceptor. Hydro in environment sensitive areas, must consider heat and oil. Environmental issues are important, especially oil containment. Deluge. a) A remote outdoor substation Physical separation (firewalls if duplicate units). Buchholz relay. Pressure relief. Separate cable terminations > 100MVA. Vented cable box. Generator circuit breaker. Bushing plus monitoring. Conservator tank isolation >100MVA. Temperature indicators. Single unit (rural) - let it burn! Double unit - physical separation / + blast wall. Sump flame trap - Important substations. Control consequential damage. Consider the layout of the surroundings. Consider building materials. Consider neighbouring natural environment. Dependent on size use pressure relief valve and shut off valve on conservator. Blast walls for smaller critical areas. d) b) A generator step-up transformer connected to a steam or gas turbine unit Possible use of Sergi protection, etc. Positioning transformers away from station. However, look at the economics. Buchholz relay. Pressure relief. Vented cable box. Generator circuit breaker. Bushing monitoring. Conservator tank isolation. Choice of oil. Temperature indicators. Fire protection (foam). GSU (Generator Step Up) transformer Generator CB (Circuit Breaker) – preferred. Blast walls and deflectors. Water sprinklers on the walls. More likely to provide fire fighting equipment for Any power transformer greater than 100MVA Physical separation (firewalls if duplicate units). Possible use of ‘Sergi’ protection, etc. Positioning transformers away from station. However, look at the economics. Environmental risks - oil contamination of lakes / rivers, etc. Containment of full volume of oil. Buchholz relay. Pressure relief. Vented cable box. Generator circuit breaker. Bushing plus monitoring. Conservator tank isolation. Choice of oil. Temperature indicators. Fire protection (foam). Blast walls and sprinklers on wall. Conservator shut off valves. Options: foam, water curtain, CO2, FR3™. Sergi system economical for larger units. 7 Electric Power Engineering Centre – Guide to Power Transformer Specification Issues Edition 2, January 2009 High velocity water spray system. C02 for sealed enclosures. Fast acting digital protection. Sergi transformer protection or gas insulated transformer. e) Indoor substation Buchholz relay. Pressure relief. Vented cable box. Generator Circuit Breaker. Bushing monitoring. Conservator tank isolation. Choice of oil. Temperature indicators. Fire protection (foam). General Notes: All scenarios require risk assessment. Consider use of polymer bushing i.e. GSA, etc. All scenarios depend on transformer size and blast wall requirements. Oil containment bunding with fire-traps/ drainage. Situational considerations – not one answer for all remote transformers or all hydro, etc. All situations consider: NFPA850 Guidelines – but these are only guidelines, but you must go through and specify. Blast walls for specified separation. Bunding w/ drainage to suffocate fire. Shutter valves on conservators. Differential Protection. 8 Electric Power Engineering Centre – Guide to Power Transformer Specification Issues PART 2.THE DETAILED DESIGN REVIEW When the Detailed Design Review process is specified: a) Employers (Clients), what Detailed Edition 2, January 2009 Provide alternatives. Assurance that the design will work and meet specifications. Provides assurance that the employer is getting what we want. Facilitates forum for improvements in design that may impact on overall cost and performance. Gain understanding of the design so we can gain understanding of test results. Find any steps in design/manufacture that you want to witness to help with maintenance. Design Review (DDR) outputs do you require and why? Using knowledge of supplier to tailor client requirements. b) Contractors (suppliers), what are the key matters that will influence the power transformer detailed Adding value to project. design that you need the Employer (Client) to Specifically reviewing: component mounting, footprints, weights, shape, oil volumes etc. clarify? Ensuring spec following best practice. Reconfirmation of 'no surprises' / confirmation that supplier has the ability to deliver. Possible provision of future on-line monitoring equipment. Compatibility with existing spares / stock, intercompatibility with existing network. What is important to client i.e. on time, cost, etc? Key scope requirements. Fit for purpose. Confirmation of spec / deviations. QA (Quality Assurance) requirements. Delivery. Drawing, documentation, manuals, maintenance procedures. Inspection process. Required specs. Transport / shipping to site. Seismic requirements. Site constraints. Weight - gross, transport. Performance criteria. Dimensions - centre of gravity. Cooling plus interlock systems. Terminations. Material listing. Specification does not cover all details. Need DDR these details, Allows agreement on these details. No DDR for standard transformers only one off/New Designs. Also discussed customer acceptance Clarification of: Out of date standards included in spec. Standard Designs i.e. 6MVA spec but a 7.5MVA standard – cheaper, faster, and easier. Component specification – e.g. bushings, colour, tap changer type – This may effect delivery and cost. Transport issues. Paint colour. Factors relating to delivery and cost. Acceptance tests. Type tests / compliance. Special tests. Material quality. Review of mechanical design. Review of loss calculations. Scope of DDR and timing of review at supplier. Compare DDR outputs to specification clauses. Special transformers need proper DDR. Report on basis of IEC and CIGRE DDR guide documents. Result is confidence in the transformer design. 9 Electric Power Engineering Centre – Guide to Power Transformer Specification Issues Need to know in spec if employer wants influence on design e.g. stress levels or specific short circuit. Need employer to have expertise or a contractor to be brought in. Edition 2, January 2009 General Notes: Should a detailed spec be required? How about the customer saying we need a transformer to fill this space, these are the connections, go to it. However, still a lot of things need to be known. Different tolerances are not always required, overbuilding, etc. It’s about relationship/confidence in supplier. QA systems, review, etc. should be done before specifications i.e. due diligence. Standardisation of one set of designs does not always work, as component costs may change meaning the set design is no longer the most economical. Where is the innovation coming from? Suppliers or Clients? Probably a combination of both. Clients drive adoption of certain items e.g. condition monitoring. Suppliers drive changes in winding types, materials, etc. In general, this is a very important process that is important for both parties. It aids clarification and understanding of how to proceed with design (contractor) and provides a certain level of optimisation for the employer (client) i.e. relationship building. 10 Electric Power Engineering Centre – Guide to Power Transformer Specification Issues PART 3. TECHNICAL SPECIFICATION EXPERIENCES a) From an Employer (Client) and / or Contractor (Supplier) perspective, what information must be given in a 2007 Technical Specification? Edition 2, January 2009 Refer to AS60076.1 appendix A as a minimum requirement. Site requirements – Footprint, Transport etc., MVA, Voltage, Losses, Vector group. Bushing types, taps, terminations, SCADA interfaces, protection devices, auxiliaries, voltage, and cooling and seismic requirements. Finishing – Painting, galvanising, wielded or bolted. Refer to standard lists. Documentation for transfer and timetable. MVA, voltage, impulse, tap changer, connection, vector group, and seismic. As built, maintenance manuals, specs, wiring specs and code. Standards AS/NZ and IEC. Intended application. Relevant standards. General characteristics / performance criteria Auxiliary components / systems. Arrangement of transformer; dimensions; bushing/terminal layouts; site requirements; system requirements. Voltage, vector group, frequency, noise requirements (sound pressure, sound power, distance), loss’s, rating, list of standards that it must comply to, Overload rating, ambient temperature, earthing, fault level, environment, seismic requirement, altitude, typical rang of impedance, tap rang, type of entry. Rating, MVA, kV. Vector group. Cooling, type of oil. Impedance. Tap-changer, plus minus percentage. Load profile. Regulation. Standards (manufacturers). List of accessories. b) Employers (Clients) and Contracts (Suppliers), Type of bushing. what times have you witnessed recently in Short circuit withstand capability. Technical Seismic. Specifications that have been unhelpful to the process? System earthing. Loss evaluation formula. Clearances - often specified when standards are in place (Designer wants a different clearance for some reason?) Guaranteed losses. Too prescriptive specs i.e. 'old school' Corrosion protection. Too many standards. Tank strength. Insistence on copper winding. Noise level. Totally useless offload sufficient. Specification of duplicate/overlapping test requirements ( contributes to additional cost/time) e.g. stating two test methods to gain same result, such as meggar vs. sweep frequency tests. Irrelevant/out of date standards. PD (Partial Discharge) test requirements NZ/AUS very low – almost impractical. Radiator specified to be both galvanised and painted. Colour of bushing in cable box. Items that are contradictory. Items that are out of date. BIL (Basic Insulation Level). Phase clearance, spacing. Creepage distances. Surge arrestors. Cable box, open bushings. CT (Current protection. Transformer) Remote tap changing. Station voltage. requirements, 11 Electric Power Engineering Centre – Guide to Power Transformer Specification Issues Edition 2, January 2009 c) Why are on-load tap changers being fitted to e) When transformers over 150MVA are specified, generator step-up transformers and what are the how should they be livened if the high voltage implications of increasing tapping ranges and network decreasing step sizes? experiences with such livening? must be used? What are some Insurance policy. Point on wave switching. Guarantees and flexibility? 480MVA back livening, audible complaint from other transformer for 10– 15 minutes. Pre-Insertion resistors. Transformer design. Old school, conservative. Asset owner compliance. More voltage regulation required. f) What are the key acceptance criteria that will Near load centres. allow Increase tap range: extreme ends of tap settings are not used. (Supplier) to close-out a project? Totally useless offload sufficient. More leads and more introduced points of potential failure. EGR (Electricity Governance Rules) requirements impact on generators ability to support/import reactive power is severe. Tap changers are not needed on generator transformers with an AVR (Automatic Voltage Regulator). d) Is single-point earthing of core, frames, and tanks a good approach? What happens when the single point earthing fails? an Employer (Client) and Contractor Setting of maintenance procedures. Drawings. Documentation. Defects. Warranty, commercial bonds, etc. Successful livening. Handover of drawings, manuals, test certificates, etc. Clear communication and well defined procedure needed. Define in contract. Pass site acceptance test. Good idea! Cost trade-off on insulation maybe. Agreed acceptance testing completed. In service for specified period and handed over. On site install / commissioning completed and documentation complete. Fence sitting: cost of coping with circulating current vs. single point. Want device that is reliable regardless of design Choice of single point earthing or not is a trade off between equipment costs and losses. The “best” will vary with circumstances. General Notes: Single point earthing lives! Need better construction to withstand transport failures, lamination failures etc, not necessarily insulation failure. Need better access for repair, replacement. On-Load Tap Changer (OLTC) - AVR might be all good, but if it has a problem, the OLTC provides good backup. But it may still not be needed as it won't be in operation if AVR is out. May need OLTC to allow for future system expansion/change. Lowers system reliability but increases system flexibility. System planners should consider this more. OLTC alters voltage seen by generator, but AVR can withstand plus minus 5% typically anyway (sometimes!). 12 Electric Power Engineering Centre – Guide to Transformer Technical Specification Edition 1, August 2007 APPENDIX A REFURBISHMENT & REPAIR OF POWER TRANSFORMERS* * Courtesy of Transfield Services Limited © Page 13 of 94 Refurbishment & Repair of Power TransformersA review of current practices in New Zealand Conference- Christchurch,2-3 July 2007 Presented by – Ramesh Gopalan Transfield Services Partners for Change Overview General Principles of Refurbishment What is being done at present Specific aspects What could be done during refurbishment Review of specifications Repair of Power Transformers - What could be done – An overview from the contractor Transfield Services Partners for Change 2 Refurbishment of transformers Transfield Services Partners for Change 3 General Principles of Refurbishment Power Transformers worldwide are ageing The average age in New Zealand is about 36 years Grid & Network operators have an ongoing programme of refurbishment for life extension. Refurbishment includes Testing the average DP of transformer insulation De-tank & Inspection of core & windings Minor modifications to blocking arrangement Changes to insulation structure- paper wound cylinders to solid cylinders Single point Earthing modifications- not always practical Transfield Services Partners for Change 4 Refurbishment of Transformers Dry-out of core & windings using heat and vacuum Re-tightening and clamping windings. Replacement of accessories- OTI, WTI, Buchholz Relay etc Replace Explosion Vent to PRV . Install Flexible Separators in Conservators OLTC replacements Corrosion control of tank and enclosures Oil reclamation to improve physical and dielectric properties. Routine Low Voltage testing following refurbishment Transfield Services Partners for Change 5 EPRI Guidelines for residual life estimates DP Value % Life Left 1000 to 1400 100% 500 60 to 66% 300 30% 200 0% Source: Guidelines for the Life Extension of Substations, 2002 Update, Electric Power Research Institute( EPRI), California, USA Transfield Services Partners for Change 6 Residual Life Estimates-NZ network transformers »Remaining life estimates are favourable for up-rating Mid Year of No. of Decade of Samples Manufacture tested 1. 2. Average tested DP value % Life Left # of years of service life left Total Service Life 1955 35 520 60% 30 80 1965 110 543 60% 30 70 1975 39 505 60% 30 65 1990* 9 719 80% 40 55 DP Values tested during refurbishment, Residual Life Assessment based on EPRI Guidelines. The above figures affirm the assessment of post 1970 transformers will have a lower life than those manufactured during 50-60’s Transfield Services Partners for Change 7 What could be done during refurbishment Refurbishment Specifications should include A review of cooling arrangement Older transformers have different style of radiators Not necessarily efficient Could be changed to more efficient Plate-fin type radiators with symmetrical arrangement ONWF arrangement could be changed to ONAN instead of OFWF Transfield Services Partners for Change 8 What could be done during refurbishment Up-rate transformers during refurbishment Generally not called for Review original Heat-run test reports Most of the transformers are ONAN cooled Could be changed to ONAN/ONAF and increase capacity Transfield Services Partners for Change 9 Dry-out of windings Dry-out is under-taken using Hot-air heating and vacuum drying thereafter Vapour phase drying is not under-taken as set up cost is prohibitive The termination of dry-out is generally based on volume of water collected per hour and a certain minimum value of vacuum usually less than 1 mbar Recommend this be changed to standard Moisture-Equilibrium curves published by IEEE Dr.Oommen curves are used by most manufacturers Eliminates the need for collecting water and monitoring water collection Cumbersome Transfield Services Partners for Change 10 Testing of transformers Transfield Services Partners for Change 11 Testing of Transformers Post refurbishment, testing is done only at low voltage Emphasis on Insulation resistance test post refurbishment Minimum acceptable value is specified based on TMI-US guidelines IR & PI values are often not achievable due to the transformer capacitance IEC standards do not specify a minimum value Minimum value for Insulation Resistance should be specified independent of kVA Rating We recommend 50Hz separate source voltage test at 75% rated value for refurbished transformers No-load excitation at 100% voltage for 30 minutes for refurbished transformers Transfield Services Partners for Change 12 Partial Discharge test Post repair, a partial discharge test is specified IEC 60076 recommends PD test for transformers with Um>300kV Some clients insist on this test for lower voltages Values specified are 50% of IEC recommended values The transformer is manufactured 25-30 years ago Only part of the winding is replaced The transformer was originally not subjected to a PD test Is it practical to achieve such low levels? The PD test is conducted in an unshielded environment Transfield Services Partners for Change 13 Repair of transformers Transfield Services Partners for Change 14 Repair of Transformers While choosing to repair, some clients Based on internal economic models, prefer the least cost option. The purchase price of transformers has doubled in the last three years Transformer Price Variation Cost of repair likely to be 20-25% of the cost of new transformer. Lead times for new transformers exceeds 12 months Repair should consider existing risk Generally recommended to replace whole windings At least the complete winding of the faulted phase Minimises risk Transfield Services Partners for Change 2.400 2.200 2.000 1.800 1.600 P r ic e In d e x 1.400 1.200 Pq/Po 1.000 0.800 0.600 0.400 0.200 0.000 Jan-04 Aug-04 Feb-05 Sep-05 Mar-06 Oct-06 Apr-07 Nov-07 Jun-08 Month-Year 15 Repair of Transformers While formulating repair specifications, we recommend Testing of the replacement winding for turns ratio, resistance and inter-strand tests This will involve the windings be put on a transformer core prior to shipping the windings to New Zealand But it is recommended We have had failures of replacement windings having Centre entry and two halves in parallel Recommend the involvement of replacement contractor in inspecting the winding prior to shipping Unequal turns between parallel halves to avoid surprises / delays upon arrival in New Zealand Specify PD levels to which transformer will be tested to the replacement winding manufacturer Transfield Services Partners for Change 16 Electric Power Engineering Centre – Guide to Transformer Technical Specification Edition 1, August 2007 APPENDIX B DRIVEN FACTORS FOR TRANSFORMER LONG LIFE** * Courtesy of Pauwels Trafo Asia © Page 30 of 94 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION ELECTRICAL DEPARTMENT – PAUWELS TRAFO ASIA Contact person ; Didik Susilo Widianto (+62.21.8230430.ext 230) ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Transformer life time The Transformer life expectation is measured by the Rate of Degradation of the Insulation normally this Insulation is cellulose paper. The expectation of transformer end life can be indicated by the degree polymerization of paper approximate 200 (and other indications). Tuesday, August 21, 2007 Introduction Power Transformer 2 Two important design driven factors ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Transformer temperature behavior ; IEC 60076 – part 2 and IEC 600354 indicate the limits based on temperature of this life time expectation. The normal life time/temperature rise & emergency capabilities at particular ambient temperatures have to be considered. Partial discharge levels ; IEC 60076 – part 3 indicates the standard limits of partial discharges for 130% Um (300 pC) and 150% Um (500 pC). These levels seem to be are very high and we would not manufacture to them. One must have low PD as with increasing moisture content, the PD rises quite dramatically at 20 ppm, 20oC moisture content mineral oil (see diagram for moisture content) while the transformer is normally tested at very good oil condition. Tuesday, August 21, 2007 Introduction Power Transformer 3 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Why is temperature important for transformer life time ??? Tuesday, August 21, 2007 Introduction Power Transformer 4 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Cellulose Conductor Insulation Ageing Tuesday, August 21, 2007 Introduction Power Transformer 5 TRANSFORMER LIFE TIME – CELLULOSE DESIGN ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION IEC 354 – Loading Guide • Section 1.2; The hottest part of the winding is used for evaluation of a relative value for rate of thermal ageing. Conductor insulation ageing • Section 2.6.2; Relative thermal ageing based on 20oC ambient + 78oC hot spot rise = 98oC. Tuesday, August 21, 2007 Introduction Power Transformer 6 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION TRANSFORMER LIFE TIME – CELLULOSE DESIGN yearly average hot spot 98oC Tuesday, August 21, 2007 Introduction Power Transformer 7 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION TRANSFORMER LIFE TIME – CELLULOSE DESIGN V=2 (θh-98)/6 yearly average hot spot 98oC Tuesday, August 21, 2007 Θh Relative ageing rate 92oC 98oC 104oC 110oC 134oC 0.5 1.0 2.0 4.0 64 Introduction Power Transformer 8 Temperature Rise and Driven Factors ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Temperature Rise for Class A (IEC 60076-2/ ANSI C57); Top oil rise ; = 60K / 55 K or 65 K. Average oil rise ; = 65 K / 55 K or 65 K (By resistance method) Hot spot rise ; = 78 K / 65K or 80K. Site elevation height; The standard elevation height is 1000 m above sea level. Climatic temperature behaviors; Yearly average ambient temperature (IEC std = 20oC) Î transformer life time. Hot monthly average ambient temperature (IEC std = 30oC) Maximum ambient temperature (IEC std = 40oC) Î transformer loading capability Temperature class; Insulation class Operating temperature Tuesday, August 21, 2007 A E B F H 105oC 120oC 125oC 145oC 220oC Introduction Power Transformer 9 Temperature Identification Hf x gradient cooler gradient Hot spot factor is normally presented between 1.1 to 1.5 depending on winding design. Tuesday, August 21, 2007 Introduction Power Transformer Hot spot Average winding Top oil Mean oil winding Bottom oil ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION core 10 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Cooling Medium INTERNAL COOLING MEDIUM Besides the thermal absorption, the internal cooling medium also functions as the insulation medium. Class A; 9Mineral oil (Inhibited or Un-inhibited oil). Class K; 9Silicon oil 9Synthetic ester 9Hi-Temp natural liquid (seeds). EXTERNAL COOLING MEDIUM 9Air 9Water Tuesday, August 21, 2007 Introduction Power Transformer 11 Terminology Of Cooling System ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Directed Cooling ; Indicates that the oil is flowing in the winding by zig-zag paths. This Directed Cooling is using Oil Barriers in several sections of winding to guide the oil flow. Non Directed Cooling ; Indicates that the oil is flowing in the winding axially. Normally, clack bands are used to improve the cooling performance. Pumped unit – Fully Directed Cooling ; Indicates that the principal part of the pumped oil from heat exchangers or radiators is forced to flow through the windings arrangement. Tuesday, August 21, 2007 Introduction Power Transformer 12 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Winding Cooling System Directed Cooling Tuesday, August 21, 2007 Non-directed Cooling Introduction Power Transformer 13 Pumped - Fully Directed Flow ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION In order to avoid > 60% of cold oil leakage, the Fully Directed Cooling is the only recommended cooling for Pumped unit. Windings ; 80% oil flow core cooler Core & leakage ; 20% oil flow winding Oil Chamber for oil flow distribution Pump Tuesday, August 21, 2007 Introduction Power Transformer 14 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Class A Standard Temperature Limits *) suitable for thermally up graded paper insulation Maximum temperature design limit [oC] Oil Winding Metal part Consequences Annual average 80 98 / 110 * 110 Life time Long Emergency 105 140 140 Gas generation Short emergency 115 160 160 Gas generation 1.Copper 115 250 160 Conductor softening 2.Aluminum 115 200 160 Thermal short circuit Tuesday, August 21, 2007 Introduction Power Transformer 15 Conservative Temperature Limits ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Temperature limits for mineral oil filled transformer with conservative safety margin to avoid any insulation degradation; 1. 125oC for maximum winding hotspot temperature during short emergency at max. 30 minutes. 2. 115oC for maximum winding hotspot temperature during continuous emergency (above time constant). Pumped - Fully Directed oil flow cooling is the most effective solution to fulfill those conservative temperature limit requirements for medium & large power transformer. The 50/100% for ONAN/ODAF cooling is the optimum combination in the case of pumped, finned radiator & fan combination (external cooling). Tuesday, August 21, 2007 Introduction Power Transformer 16 Recommended Cooling Method ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Directed cooling; For pumped unit (OD), the Fully Directed windings with oil Directed to the windings and through the windings is the most optimum for medium & large transformer with conservative temperature limits & severe overloading requirements. For in case natural oil flow unit, we also produce Directed in the windings only. Some time ago (up to 2000), we had built Non Directed/Axial cooling with Clack band cooling systems. Value for money in any system, Fully Directed Oil flow gives the most effective commercial result and provides significant design benefits in fully fitting the severe overloading requirements. Tuesday, August 21, 2007 Introduction Power Transformer 17 Recommended Cooling Method ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Directed cooling; 1. As there is an oil gap in the middle of the winding due to clack band which is required for additional cooling, the buckling withstand is more difficult to control. There are difficulties controlling alignment of the clack band due to the fixed distance between the clacks. 2. The usage of clack band for the axial cooling duct of Non Directed cooling reduces the series capacitance of the winding. Due to this reduction in series capacitance, more insulation is required to strengthen the insulation coordination against impulse switching surges and high frequency voltage spikes inherent in the system. Tuesday, August 21, 2007 Introduction Power Transformer 18 Recommended Cooling Method ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Directed cooling; 3. Under OD, we are more able to accurately predict and control our low gradients. A low gradient allows one to more easily control the temperature behavior and cater for severe overloading conditions. The value of the gradient is that as the current increases, the gradient rises by the power of 1.6 for Non-Directed cooling, 1.2 for natural flow Directed cooling and 2.0 for Fully Directed pumped oil flow. The gradient of a competitive unit of Non Directed cooling is typically almost double the Fully Directed (OD) unit and ,if one overloads, the gradient temperature increase can be quite dramatic and limits overload capacity. Tuesday, August 21, 2007 Introduction Power Transformer 19 Recommended Cooling Method ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Directed cooling; 4. Fully Directed flow units can be made electrically stronger than Non Directed flow units as the duct size on either side of the winding can be significantly reduced (increased strength per mm). In naturally cooled units ie ONAN and ONAF, the duct normally need to be increased for cooling considerations due to very low thermosyphonic oil flow. 5. It is the fact that the pumped – fully Directed flow unit will eliminate the local overheated oil around the hot spot area. This system is suitable for Hybrid design technology in mobile transformer application or other compact transformer. Tuesday, August 21, 2007 Introduction Power Transformer 20 Recommended Cooling Method ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Directed cooling; 6. Due to it’s high cooling effectiveness, the Fully Directed flow pumped units in combination with low RPM big fans is mostly able to minimize the cooling noise fitting with extremely low noise requirements. This solution is the most preferred solution rather than reducing the induction and increasing the active material (core & copper) as consequences. ODAN cooling gives practically lower noise increase at approx. 20% rating above ONAN in comparison with ONAF solution. Note : - we build all types of units, ONAN, ONAF and ODAF Tuesday, August 21, 2007 Introduction Power Transformer 21 Winding Gradient ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Grad. = Function (q, 1/ψ , 1/ρ , 1/c ,η) “Grad.” Liquid to conductor gradient temperature [K] “q” Distributed losses density [W/mm2] “ψ” Distributed liquid mass flow rate [mm/s] ”ρ” Liquid mass density [kg/mm3] “c” Specific heat capacity [J/kg.K] “η” Coefficient of convective heat transfer [W/mm2] Tuesday, August 21, 2007 Introduction Power Transformer 22 Surface Heat Transfer Coefficient ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION η (surface heat transferred coefficient) is a function of duct size, oil flow length & velocity. For directed (zig-zag) cooling ; The axial and radial surface of the winding conductor are considered as the surfaces for heat transfer. This can be quite accurately calculated to determine the winding gradient of the winding. For non-directed (axial) cooling ; The axial surface of the winding conductor section is predominantly considered as the main heat transfer surface. Tuesday, August 21, 2007 Introduction Power Transformer 23 Mass Flow Rate ON Cooling ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION 1. Determined by thermosyphonic principle of Buoyancy effect. 2. Driven by winding heat due to losses (I2R + eddy losses) and cooling medium properties (mass density, viscosity). OD Cooling 1. Determined by thermo-hydrodynamic calculation at equilibrium hydraulic pressure. 2. Driven by winding heat due to losses (I2R + eddy losses), designed oil speed, pump capacity and cooling medium properties (mass density, viscosity, specific heat capacity). Tuesday, August 21, 2007 Introduction Power Transformer 24 Typical OD Mass Flow Rate Distribution ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION 270 mm/s 180 mm/s 110 mm/s OD design Tuesday, August 21, 2007 Introduction Power Transformer 25 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Flow Barrier in Directed Cooled Winding Outside Flapped type barrier Inside Flapped type barrier Tuesday, August 21, 2007 Introduction Power Transformer 26 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Partition Ring to Control Thermal Balance Between Windings Tuesday, August 21, 2007 Introduction Power Transformer 27 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Fully Oil Directed Cooled All Windings Oil Directed Twin Boosters Tuesday, August 21, 2007 Introduction Power Transformer 28 Gradient Comparison Of Directed vs Non-directed Cooling In Natural Flow ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION 60/90 MVA, 132/33 kV ONAN/ONAF + 150% CMR two hours emergency LV HV Directed Calc. Meas. Non-directed Calc. A Calc. B AN 0.67 pu 12.6 oC 11.0 oC 19.5 oC 7.9 oC AF 1.00 pu 15.6 oC 14.2 oC 29.4 oC 15.0 oC AF 1.50 pu 24.3 oC 23.4 oC 43.8 oC 28.7 oC CU net weight 2092 kgs 2092 kgs 2550 kgs # Clack band NA NA 3 pcs AN 0.67 pu 10.7 oC 10.3 oC 22.3 oC 7.9 oC AF 1.00 pu 16.7 oC 15.0 oC 33.7 oC 15.1 oC AF 1.50 pu 26.6 oC 25.0 oC 55.5 oC 28.9 oC CU net weight 2816 kgs 2816 kgs 3450 kgs # Clack band NA NA 2 pcs Tuesday, August 21, 2007 Introduction Power Transformer 29 Comparison Of Experienced Cooling System Factory Test Results ONAN/ONAF ONAN/ODAF 150 MVA 230/115 kV 250 MVA 220/114 kV Double Wound Auto Transformer Top Oil Rise 42.65 oC 46.8 oC Winding Gradient 19.2 oC 12.6 oC Hot Spot Rise 67.6 oC 63.2 oC Non-Directed Fully Directed # Clack band 5 x 5.4 mm thick. NA Top Oil Rise 42.65 oC 46.8 oC Winding Gradient 22.5 oC 18.9 oC Hot Spot Rise 71.9 oC 71.4 oC Non-Directed Fully Directed 4 x 5.9 mm thick. NA Transformer Rating Type Of Transformer ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION LV Winding Cooling HV Winding Cooling # Clack band External Cooling Tuesday, August 21, 2007 12 rad. + 30 small fans 1(+1) pumps + 8 rad.+ 4 fans Introduction Power Transformer 30 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION 150 MVA DOUBLE WOUND TRANSFORMER NON DIRECTED COOLING End user : CHEVRON Indonesia. (Energized 2000) 90/150 MVA ONAN/ONAF DOUBLE WOUND TRANSFORMER HV : 230 + 16 x 0.625% kV OLTC. IV : 115 kV / LV : 13.8 + 2 x 2.5% kV DETC Tuesday, August 21, 2007 Introduction Power Transformer 31 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION 250 MVA AUTOTRAFO – FULLY DIRECTED End user : TransPower New Zealand. (Energized 2005) 250 MVA ONAN/ODAF AUTOTRANSFORMER HV : 220 + 8 x 1.25% kV OLTC. IV : 114 kV / LV : 11 + 2 x 2.5% kV (capacitive load) Tuesday, August 21, 2007 Introduction Power Transformer 32 Fiber Optic Installation Purpose : ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION To directly measure the Hot Spot temperature, fibre optics can be used to measure temperatures in cores and tank walls - not only the windings of the transformer. Tuesday, August 21, 2007 Introduction Power Transformer 33 Infra Red Thermal Investigation ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Typical Infra Red Thermal Check To avoid local overheating Tuesday, August 21, 2007 Introduction Power Transformer 34 Extendable Plate type Water Cooler ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Possibility to extend the cooler capacity at site to reduce the transformer temperature Tuesday, August 21, 2007 Introduction Power Transformer 35 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Why is Partial Discharge important for transformer life time ??? Tuesday, August 21, 2007 Introduction Power Transformer 36 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Partial Discharge Partial Discharge level will measure the activity of electron discharging from the conductive materials thru the dielectric medium. Inside the transformer, the cellulose insulation and mineral oil are the dielectric medium and this partial discharge will ionize their hydrocarbon molecules. High Partial Discharge Level will destroy the hydrocarbon chains of the transformer insulation and cause the electric breakdown ignition. When there is moisture involved, the insulation degradation rate will be much faster. Tuesday, August 21, 2007 Introduction Power Transformer 37 Six Categories Of Partial Discharges Partial Discharge indicates the defects existence prior to dielectric breakdown. breakdown ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION 1. Corona discharges occurs due to the sharp edge electrode. 2. Surface discharges (creepage) occurs due to overstress component parallel to the dielectric medium surface. 3. Internal discharges occurs due to the non-homogenous dielectric medium. 4. Electric trees due to the particle or cavity in the solid insulation. 5. Floating discharging occurs due to badly grounded component. 6. Contact noise occur in case bad contact terminal. Tuesday, August 21, 2007 Introduction Power Transformer 38 Optimized Oil Duct Thickness ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION The oil duct thickness has to not only provide reliable cooling but has to provide electrical insulation. The diagram shows how a smaller duct provides higher voltage strength per mm. Tuesday, August 21, 2007 Introduction Power Transformer 39 Moisture Content In Paper [%weight] ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Equilibrium Of Moisture Content In Oil vs. Paper The transformer is tested normally at less than 5 ppm moisture content in oil Moisture Content In Mineral Oil [ppm weight] Tuesday, August 21, 2007 Introduction Power Transformer 40 Power Freq. Withstand Voltage [%] ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Oil Moisture Content vs Dielectric Strength Moisture Content In Oil [ppm] Tuesday, August 21, 2007 Introduction Power Transformer 41 Power Freq. Withstand Voltage [%] ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Paper Moisture Content vs Dielectric Strength Moisture Content In Oil Impregnated Paper [%] Tuesday, August 21, 2007 Introduction Power Transformer 42 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Typical Of Low Partial Discharge Tuesday, August 21, 2007 Introduction Power Transformer 43 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Discharging Circle Prior To Flashover High Partial Discharge Insulation Ionization Insulation weakening Tuesday, August 21, 2007 Gassing Introduction Power Transformer 44 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION CONCLUSION FOR MINERAL OIL XMER Temperature limits; The temperature limits and the type of overloading at particular ambient temperature have to be indicated. New class A cellulose paper covered conductor immersed in new mineral oil will start gassing at hot spot temperature of 145oC. Cooling system; Fully directed cooling with pump is the most suitable for medium & large transformer. The directed cooling with no pump can be used for cost effectivenes consideration on small/medium transformer. Conductor paper ; The cellulose paper should have Degree Polymerization min. 950. Low partial discharge product shall be performanced at factory test; => 40 pC up to 120% Voltage for 30 minutes. => 75 pC up to 150% Voltage for 30 minutes. => to monitor the partial discharge at induced level, 1min. Tuesday, August 21, 2007 Introduction Power Transformer 45 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Doubled Capacity On Existing Foundation End User : COMALCO ALUMINIUM SMELTER AUSTRALIA 168 MVA ODAF, 220 kV / 2.7 to 40.4 kV in 3 x 52 steps via 2 x OLTCs + DETC. This was installed on existing foundation of a 110 MVA regulator . Tuesday, August 21, 2007 Introduction Power Transformer 46 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION FUTURE FUTURE SOLUTIONS SOLUTIONS ?? Tuesday, August 21, 2007 Introduction Power Transformer 47 Hybrid Design ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION CALENDERED KRAFT BOARD CALENDERED KRAFT BOARD Angle Rings and Caps Support Washers NOMEX® T-993 Creped NOMEX® Static Rings CALENDERED KRAFT BOARD Cylinders NOMEX® T-410 Conductor Insulation NOMEX® T-994 Axial & Radial Spacers PRECOMPRESSED KRAFT BOARD Tuesday, August 21, 2007 Clamping Rings, Blocks Introduction Power Transformer 48 Hybrid Design – Engineering Transformer 97oC hot spot rise ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Cellulose pressboard Capacity = 12.5 MVA (ONAN) Voltage = 115 + 1.4 / 21.5 kV BIL HV/LV = 550 / 125 kV Vector group = YNd11 HV winding = Disc / PI 0.8 / ksp. 2.0 LV winding = Disc / PI 0.5 / ksp. 1.5 Cooling = ONAN in 10 radiators Top oil rise = 57 K Average HV rise = 62.1 K Cellulose insulated lead outs Average LV rise = 70.1 K Measured HV grad. = 25 K Measured LV grad. = 33 K Hot spot factor = 1.2 Tuesday, August 21, 2007 Introduction Power Transformer 49 CASE STUDY – 30 MVA for PG&E Built by Pauwels for Pacific Gas & Electric ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Power (MVA) Weight (T) Cellulose design with same weight with same MVA Cellulose design with same MVA 45 45 31,5 44,1 57,5 44,1 Hybrid design IZ (%) 19,1 10,0 10,0 No load losses (kW) 11,9 10 8 Load losses (kW) 752 225 110 95 65 65 Temperature rises (K) Tuesday, August 21, 2007 Introduction Power Transformer 50 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Hybrid Design In Mobile Transformer Under Substation Installation Tuesday, August 21, 2007 Introduction Power Transformer 51 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Hybrid Design In Mobile Transformer Test Drive Tuesday, August 21, 2007 Introduction Power Transformer 52 DGA Report – Typical Hybrid design The gas generation produced by Hybrid transformers after temperature rise test at PAUWELS factory. ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION 50 MVA, 161-115/13.8-34.5 kV, Inert air system, Nitro 10XT oil Gas Symbol Temperature rise test (8 hours) Increment Cellulose Before After unit in ppm/hour Typical <2 Hydrogen H2 < 0.8 10.13 ppm 1.27 Oxygen O2 0.96 0.77 % - Nitrogen N2 2.15 1.61 % - Carbon monoxide CO 7.17 9.40 ppm 0.27 <2 Carbon dioxide CO2 122.32 205.78 ppm 10.43 < 11 Methane CH4 1.75 2.01 ppm 0.03 < 0.25 Acetylene C2H2 0.08 0.11 ppm - < 0.25 Ethylene C2H4 0.11 0.10 ppm - < 0.25 Ethane C2H6 0.12 0.11 ppm - < 0.25 Tuesday, August 21, 2007 Introduction Power Transformer 53 Future – Environmental Friendly Liquid ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION • Environmental liquid = Enviro-Temp FR3 by COOPER • Inhibited oil = Nitro 10XT by NYNAS Property – typical values Inhibited oil FR3 Antioxidant, phenols 0.08% per Wt n.a. 500 hours continuous Biodegradable in 21 days 25% 100% Saturated moisture at 25oC 80 ppm 1200 ppm 60/65/78 K 80/110/130 K Flash point 145oC 330oC Pour point -57oC -18oC Oxidation stability by 120oC Temp. rise for unity life time *) *) Top oil/Average winding/hot spot rise (+ Hybrid design for FR3) Tuesday, August 21, 2007 Introduction Power Transformer 54 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Water Saturation of Mineral oil vs FR3 Tuesday, August 21, 2007 Introduction Power Transformer 55 Liquid Water Absorption versus Time Exposure Water Absorption of Dielectric Fluids Exposed to Ambient Air (2 of 2) Envirotemp FR3 fluid conventional transformer oil 80 60 Water Absorption of Dielectric Fluids Exposed to Ambient Air (1 of 2) 600 40 20 0 0 500 1000 1500 2000 Exposure Time (hrs) 2500 3000 3500 Absolute Water Content (ppm) R e la tiv e W a te r C o n te n t ( % s a tu ra tio n ) ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION 100 500 400 300 Envirotemp FR3 fluid conventional transformer oil 200 100 0 0 100% Saturation = FR3, 1200 ppm Mineral Oil, 80 ppm Tuesday, August 21, 2007 500 Introduction Power Transformer 1000 1500 2000 2500 3000 3500 Exposure Time (hrs) 56 Liquid Dielectric Strength vs. Water Content Dielectric Strength versus Water Content D 1816 Dielectric Breakdown (kV) ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION 80 70 60 50 40 30 Envirotemp FR3 fluid conventional transformer oil 20 10 0 0 100 200 300 400 500 600 Water Content (ppm) Tuesday, August 21, 2007 Introduction Power Transformer 57 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Partial Discharge Of FR3 Filled Transformer Tuesday, August 21, 2007 Introduction Power Transformer 58 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Prototype transformer filled with FR3 12/17 MVA, 33kV,ONAN/ONAF + provision for future ODAF Measured PD = 25 pC max. at induced voltage level. Liquid Main tank = Enviro Temp - FR3 (Hi-Temp natural – ester based 100% biodegradable) Tuesday, August 21, 2007 Introduction Power Transformer 59 ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION Tuesday, August 21, 2007 Introduction Power Transformer 60 Low partial discharge product ; ÎAssists to increase a units life from overvoltage spikes and prolongs oil quality • Typical guaranteed partial discharge ; ENERGY IS OUR BUSINESS, QUALITY IS OUR MISSION 9 75 pC at 150% Un, IEC 60076 500 pC at 150% Um 9 40 pC at 120% Un, IEC 60076 100 pC at 110% Um • Typical achievement , by rating voltage = 220 kV (950 kVp BIL); 914 pC at 150% voltage. 927 pC at 200% voltage. Dirrected cooling path ; Î Assists life time expectation under overloading conditions and suitable for Low noise requirement. Compact design, safety and enviromental friendly; Î Usage Hybrid design and Vegetable liquid to minimize the land space required, less flammable risk and enviromental friendly unit. Tuesday, August 21, 2007 Introduction Power Transformer 61 Electric Power Engineering Centre – Guide to Transformer Technical Specification Edition 1, August 2007 APPENDIX C EPECENTRE ELECTRIC POWER R&D CAPABILITY Page 92 of 94 New Zealand’s Centre of Excellence for Power Engineering Electric Power R&D Programme Energy Efficient Generation & Distribution Power Systems Reliability System Studies Demand Side Management Alternative Power Generation Power Transformers HV Testing Power Quality Renewable Energy Energy Modelling www.epecentre.ac.nz Supporting Industry R&D needs for NZ’s Energy Future… Launched New Zealand’s first collaborative industry-academia R&D Programme for power in 2005… Our Services Short-term projects in specialist areas (see overleaf); customised technical workshops & training; design & testing; technical advise and support. About Us Formed in 2002, the EPECentre is an industry funded Centre of Excellence for power engineering in New Zealand, hosted at the University of Canterbury in Christchurch. It is focused on power engineering education, research & development, innovation, and industry interaction. Our People The EPECentre has a dedicated team of R&D power engineers, technical power systems specialists, research scholars, and in-house project management and technical support – a combined team of over 25 power engineers within campus, combined with a reputation for one of the leading power engineering programmes in the southern hemisphere. Our Facilities World class facilities and equipment, including a state-of-the-art electric machines laboratory and a HV laboratory with an impressive 1.4MV Impulse Generator - Plus: industry standard test equipment, including power harmonics analysers, signal generators, oscilloscopes, and software for harmonic analysis, power flow, and fault analysis, such as PSCAD, IPSA, Power Factory, and PSPICE. Past Clients Orion, Transpower NZ, Meridian Energy, Vector, Enermet, ElectraNet SA, Metrix, ACCG, Antarctica NZ, Canterbury TX, Pearson Innovations, CAE NZ... www.epecentre.ac.nz our industry partners: Electric Power Engineering Centre (EPECentre) University of Canterbury, Private Bag 4800, Christchurch, New Zealand Tel: +64 21 1144 330 Email: joseph.lawrence@epecentre.ac.nz