Guide to Transformer Specification

GGuuiiddee ttoo PPoowweerr TTrraannssffoorrmmeerr SSppeecciiffiiccaattiioonn IIssssuueess

www.epecentre.ac.nz

Electric Power Engineering Centre – Guide to Power Transformer Specification Issues Edition 2, January 2009

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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 © 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.

Electric Power Engineering Centre University of Canterbury Private Bag 4800 Christchurch New Zealand T: +64 3 366 7001 E: [email protected] www.epecentre.ac.nz


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Electric Power Engineering Centre -

GUIDE TO POWER TRANSFORMER SPECIFICATION ISSUES 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 ©

CCOONNTTEENNTTSS


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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,

Wade Enright

Dr. Wade G. Enright

Associate, Electric Power Engineering Centre, University of Canterbury

August 2007

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.


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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.


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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.


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SETTING THE SCENE 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.”

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.”

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.

The repair bill is significant.

What is the Industry going to do about it?

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? 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?

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?


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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 following scenarios?

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.

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

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.

c) A generator step-up transformer connected to a 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.

d) 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.


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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.


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PART 2.THE DETAILED DESIGN REVIEW When the Detailed Design Review process is specified: a) Employers (Clients), what Detailed Design

Review (DDR) outputs do you require and why? Using knowledge of supplier to tailor client

requirements.

Adding value to project.

Specifically reviewing: component mounting, footprints, weights, shape, oil volumes etc.

Reconfirmation of 'no surprises' / confirmation that supplier has the ability to deliver.

Compatibility with existing spares / stock, inter-compatibility with existing network.

Key scope requirements.

Fit for purpose.

Delivery.

Inspection process.

Transport / shipping to site.

Site constraints.

Performance criteria.

Cooling plus interlock systems.

Material listing.

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.

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. b) Contractors (suppliers), what are the key matters

that will influence the power transformer detailed design that you need the Employer (Client) to clarify?

Ensuring spec following best practice.

Possible provision of future on-line monitoring equipment.

What is important to client i.e. on time, cost, etc?

Confirmation of spec / deviations.

QA (Quality Assurance) requirements.

Drawing, documentation, manuals, maintenance procedures.

Required specs.

Seismic requirements.

Weight - gross, transport.

Dimensions - centre of gravity.

Terminations.

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.


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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.

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.


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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?

Refer to standard lists.

MVA, voltage, impulse, tap changer, connection, vector group, and seismic.

Intended application.

Rating, MVA, kV.

Vector group.

Cooling, type of oil.

Impedance.

Tap-changer, plus minus percentage.

Load profile.

Regulation.

Standards (manufacturers).

List of accessories.

Type of bushing.

Short circuit withstand capability.

Seismic.

System earthing.

BIL (Basic Insulation Level).

Loss evaluation formula.

Guaranteed losses.

Corrosion protection.

Tank strength.

Noise level.

Phase clearance, spacing.

Creepage distances.

Surge arrestors.

Cable box, open bushings.

CT (Current Transformer) requirements, protection.

Remote tap changing.

Station voltage.

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.

Documentation for transfer and timetable.

As built, maintenance manuals, specs, wiring specs and code. Standards AS/NZ and IEC.

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.

b) Employers (Clients) and Contracts (Suppliers), what times have you witnessed recently in Technical Specifications that have been unhelpful to the process?

Clearances - often specified when standards are in place (Designer wants a different clearance for some reason?)

Too prescriptive specs i.e. 'old school'

Too many standards.

Insistence on copper winding.

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.


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c) Why are on-load tap changers being fitted to generator step-up transformers and what are the implications of increasing tapping ranges and decreasing step sizes?

Insurance policy.

Guarantees and flexibility?

Transformer design.

Old school, conservative.

Asset owner compliance.

More voltage regulation required.

Near load centres.

Increase tap range: extreme ends of tap settings are not used.

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?

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.

e) When transformers over 150MVA are specified, how should they be livened if the high voltage network must be used? What are some experiences with such livening?

Point on wave switching.

480MVA back livening, audible complaint from other transformer for 10– 15 minutes.

Pre-Insertion resistors. f) What are the key acceptance criteria that will

allow an Employer (Client) and Contractor (Supplier) to close-out a project?

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.

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!).

Electric Power Engineering Centre – Guide to Transformer Technical Specification Edition 1, August 2007

Page 13 of 94

APPENDIX A

REFURBISHMENT & REPAIR OF POWER TRANSFORMERS* * Courtesy of Transfield Services Limited ©

Transfield Services Partners for Change

Refurbishment & Repair of Power Transformers-A review of current practices in New Zealand

Conference- Christchurch,2-3 July 2007

Presented by – Ramesh Gopalan

Transfield Services Partners for Change2

Overview

General Principles of RefurbishmentWhat is being done at present

Specific aspectsWhat could be done during refurbishment

Review of specifications

Repair of Power Transformers - What could be done – An overview from the contractor


Refurbishment of transformers


General Principles of Refurbishment

Power Transformers worldwide are ageingThe 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 insulationDe-tank & Inspection of core & windingsMinor modifications to blocking arrangementChanges to insulation structure- paper wound cylinders to solid cylindersSingle point Earthing modifications- not always practical


Refurbishment of Transformers

Dry-out of core & windings using heat and vacuumRe-tightening and clamping windings.Replacement of accessories- OTI, WTI, Buchholz Relay etc

Replace Explosion Vent to PRV .Install Flexible Separators in ConservatorsOLTC replacements

Corrosion control of tank and enclosuresOil reclamation to improve physical and dielectric properties.Routine Low Voltage testing following refurbishment


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


Residual Life Estimates-NZ network transformers

Mid Year of Decade of

Manufacture

No. of Samples

tested

Average tested DP

value

% Life Left # of years of service

life left

Total Service

Life

1955 35 520 60% 30

30

30

40

80

1965 110 543 60% 70

1975 39 505 60% 65

1990* 9 719 80% 55

1. DP Values tested during refurbishment, Residual Life Assessment based on EPRI Guidelines.

2. The above figures affirm the assessment of post 1970 transformers will have a lower life than those manufactured during 50-60’s

»Remaining life estimates are favourable for up-rating


What could be done during refurbishmentRefurbishment Specifications should include

A review of cooling arrangementOlder transformers have different style of radiators

Not necessarily efficientCould be changed to more efficient Plate-fin type radiators with symmetrical arrangementONWF arrangement could be changed to ONAN instead of OFWF


What could be done during refurbishment

Up-rate transformers during refurbishment

Generally not called forReview original Heat-run test reportsMost of the transformers are ONAN cooledCould be changed to ONAN/ONAF and increase capacity


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 prohibitiveThe 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 manufacturersEliminates the need for collecting water and monitoring water collection

Cumbersome


Testing of transformers


Testing of Transformers

Post refurbishment, testing is done only at low voltageEmphasis 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 RatingWe recommend

50Hz separate source voltage test at 75% rated value for refurbished transformersNo-load excitation at 100% voltage for 30 minutes for refurbished transformers


Partial Discharge test

Post repair, a partial discharge test is specifiedIEC 60076 recommends PD test for transformers with Um>300kV

Some clients insist on this test for lower voltagesValues specified are 50% of IEC recommended values

The transformer is manufactured 25-30 years agoOnly part of the winding is replaced The transformer was originally not subjected to a PD testIs it practical to achieve such low levels?

The PD test is conducted in an unshielded environment


Repair of transformers


Repair of TransformersWhile 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

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 riskGenerally recommended to replace whole windings

At least the complete winding of the faulted phaseMinimises risk

Transformer Price Variation

0.000

0.200

0.400

0.600

0.800

1.000

1.200

1.400

1.600

1.800

2.000

2.200

2.400

Jan-04 Aug-04 Feb-05 Sep-05 Mar-06 Oct-06 Apr-07 Nov-07 Jun-08

Month-Year

Pric

e In

dex

Pq/Po


Repair of Transformers

While formulating repair specifications, we recommendTesting of the replacement winding for turns ratio, resistance and inter-strand tests

prior to shipping the windings to New ZealandThis will involve the windings be put on a transformer core

But it is recommendedWe have had failures of replacement windings having

Centre entry and two halves in parallelUnequal turns between parallel halves

Recommend the involvement of replacement contractor in inspecting the winding prior to shipping

to avoid surprises / delays upon arrival in New ZealandSpecify PD levels to which transformer will be tested to the replacement winding manufacturer


Page 30 of 94

APPENDIX B

DRIVEN FACTORS FOR TRANSFORMER LONG LIFE**

* Courtesy of Pauwels Trafo Asia ©

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ELECTRICAL DEPARTMENT – PAUWELS TRAFO ASIAContact person ; Didik Susilo Widianto (+62.21.8230430.ext 230)

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Tuesday, August 21, 2007 Introduction Power Transformer 2

Transformer life timeTransformer life time

The Transformer life expectation is measured by the Rate of Degradation of the Insulation

normally this Insulation is cellulose paper.cellulose paper.

The expectation of transformer end life can be indicated by the degree polymerization of paper

approximate 200 (and other indications).

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Two important design driven factorsTransformer temperature behavior ;Transformer temperature behavior ;

IEC 60076 IEC 60076 –– part 2 and IEC 600354 indicate the limits based on part 2 and IEC 600354 indicate the limits based on temperature of this life time expectation. The normal life temperature of this life time expectation. The normal life time/temperature rise & emergency capabilities at particular ambtime/temperature rise & emergency capabilities at particular ambient ient temperatures have to be considered.temperatures have to be considered.

Partial discharge levels ;Partial discharge levels ;IEC 60076 IEC 60076 –– part 3 indicates the standard limits of partial part 3 indicates the standard limits of partial discharges for 130% Um (300 discharges for 130% Um (300 pCpC) and 150% Um (500 ) and 150% Um (500 pCpC). These ). These levels seem to be are very high and we would not manufacture to levels seem to be are very high and we would not manufacture to them.them. One must have low PD as with increasing moisture content, One must have low PD as with increasing moisture content, the PD rises quite dramatically at 20 the PD rises quite dramatically at 20 ppmppm, 20, 20ooC moisture content C moisture content mineral oil (see diagram for moisture content) while the transfomineral oil (see diagram for moisture content) while the transformer rmer is normally tested at very good oil condition.is normally tested at very good oil condition.

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Why is temperature important for Why is temperature important for transformer life time ???transformer life time ???

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Cellulose Conductor Insulation AgeingCellulose Conductor Insulation Ageing

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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.

TRANSFORMER LIFE TIME TRANSFORMER LIFE TIME –– CELLULOSE DESIGNCELLULOSE DESIGN

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TRANSFORMER LIFE TIME TRANSFORMER LIFE TIME –– CELLULOSE CELLULOSE DESIGNDESIGN

yearly average hot spot 98oC

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TRANSFORMER LIFE TIME TRANSFORMER LIFE TIME –– CELLULOSE CELLULOSE DESIGNDESIGN

V = 2(θh-98)/6 ΘhRelative ageing rate

92oC 0.598oC 1.0104oC 2.0110oC 4.0134oC 64yearly average hot spot 98oC

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Temperature Rise and Driven FactorsTemperature Rise and Driven FactorsTemperature 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) transformer life time.transformer life time.Hot monthly average ambient temperature (IEC std = 30oC)Maximum ambient temperature (IEC std = 40oC) transformer loading capabilitytransformer loading capability

Temperature class;

Insulation class A E B F H

Operating temperature 105oC 120oC 125oC 145oC 220oC

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Temperature IdentificationTemperature Identification

windingwinding

corecore

coolercooler

Bot

tom

oil

Bot

tom

oil

Top

oil

Top

oil

Ave

rage

win

ding

Ave

rage

win

ding

Hot

spot

Hot

spot

Mea

n oi

lM

ean

oil

HHff x gradientx gradient

gradientgradient

Hot spot factor is normally presented between 1.1 to 1.5 depending on winding design.

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Cooling MediumCooling Medium

INTERNAL COOLING MEDIUMBesides the thermal absorption, the internal cooling medium also functions as the insulation medium.Class A;Class A;

Mineral oil (Inhibited or UnMineral oil (Inhibited or Un--inhibited oil).inhibited oil).Class K;Class K;

Silicon oilSilicon oilSynthetic esterSynthetic esterHiHi--Temp natural liquid (seeds).Temp natural liquid (seeds).

EXTERNAL COOLING MEDIUMAirWater

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Terminology Of Cooling System Terminology Of Cooling System Directed Cooling ;

Indicates that the oil is flowing in the winding by zig-zagpaths. 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.

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Winding Cooling SystemWinding Cooling System

Directed Cooling Non-directed Cooling

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Pumped Pumped -- Fully Directed FlowFully Directed Flow

corecore

In order to avoid > 60% of cold oil leakage, theIn order to avoid > 60% of cold oil leakage, the Fully Directed Fully Directed Cooling Cooling is the only recommended cooling for Pumped unit.is the only recommended cooling for Pumped unit.

Windings ; 80% oil flow

Core & leakage ; 20% oil flow

Oil Chamber for oil flow distribution

Pump

windingwinding

coolercooler

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Class A Standard Temperature LimitsClass A Standard Temperature Limits

Maximum temperature design limit [oC]*) suitable for *) suitable for thermally up graded thermally up graded paperpaper insulationinsulation Oil Winding Metal part Consequences

110

Long Emergency 105 140 140 Gas generation

Short emergency 115 160 160 Gas generation

Thermal short circuitConductor softening1.Copper 115 250 160

160

Life timeAnnual average 80 98 / 110 *

2.Aluminum 115 200

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Conservative Temperature LimitsConservative Temperature Limits

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).

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).

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Recommended Cooling MethodRecommended Cooling Method

Directed cooling;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 theValue for money in any system, Fully Directed Oil flow gives themost effective commercial result and provides significant designmost effective commercial result and provides significant design

benefits in fully fitting the severe overloading requirements.benefits in fully fitting the severe overloading requirements.

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Directed cooling;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.

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Recommended Cooling MethodRecommended Cooling MethodDirected cooling;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.

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Directed cooling;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.

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Directed cooling;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

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Winding GradientWinding Gradient

Grad. = Function (q, 1/Grad. = Function (q, 1/ψψ , 1/, 1/ρρ , 1/c ,, 1/c ,ηη))

“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]

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Surface Heat Transfer CoefficientSurface Heat Transfer Coefficient

η η (surface heat transferred coefficient) is a (surface heat transferred coefficient) is a function of duct size, oil flow length & velocity.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.

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Mass Flow RateMass Flow Rate

ON Cooling

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).

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Typical OD Mass Flow Rate DistributionTypical OD Mass Flow Rate Distribution

270 mm/s

180 mm/s

110 mm/s

OD design

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Flow Barrier in Directed Cooled WindingFlow Barrier in Directed Cooled Winding

Inside Flapped type barrier

Outside Flapped type barrier

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Partition Ring to Control Thermal Partition Ring to Control Thermal Balance Between Balance Between Windings

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Fully Oil Directed Cooled All WindingsFully Oil Directed Cooled All Windings

Oil Directed Oil Directed Twin BoostersTwin Boosters

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Gradient Comparison Of Directed Gradient Comparison Of Directed vsvsNonNon--directed Cooling In Natural Flowdirected Cooling In Natural Flow

Directed Non-directed Calc. Meas. Calc. A Calc. B

AN 0.67 pu 12.6 oC 11.0 oC 19.5 oC 7.9 oCAF 1.00 pu 15.6 oC 14.2 oC 29.4 oC 15.0 oCAF 1.50 pu 24.3 oC 23.4 oC 43.8 oC 28.7 oCCU net weight 2092 kgs 2092 kgs 2550 kgs# Clack band NA NA 3 pcsAN 0.67 pu 10.7 oC 10.3 oC 22.3 oC 7.9 oCAF 1.00 pu 16.7 oC 15.0 oC 33.7 oC 15.1 oC

HV

AF 1.50 pu 26.6 oC 25.0 oC 55.5 oC 28.9 oCCU net weight 2816 kgs 2816 kgs 3450 kgs# Clack band NA NA 2 pcs

LV

60/90 MVA, 132/33 kVONAN/ONAF + 150% CMRtwo hours emergency

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Comparison Of Experienced Cooling SystemComparison Of Experienced Cooling SystemFactory Test Results ONAN/ONAF ONAN/ODAFTransformer Rating 150 MVA 230/115 kV 250 MVA 220/114 kV

HVHV

# Clack band 4 x 5.9 mm thick. NA

Type Of Transformer Double Wound Auto TransformerTop Oil Rise 42.65 oC 46.8 oCWinding Gradient 19.2 oC 12.6 oCHot Spot Rise 67.6 oC 63.2 oCWinding Cooling Non-Directed Fully Directed# Clack band 5 x 5.4 mm thick. NATop Oil Rise 42.65 oC 46.8 oCWinding Gradient 22.5 oC 18.9 oC

External CoolingExternal Cooling

Hot Spot Rise 71.9 oC 71.4 oCWinding Cooling Non-Directed Fully Directed

12 rad. + 30 small fans 1(+1) pumps + 8 rad.+ 4 fans

LVLV

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150 MVA DOUBLE WOUND TRANSFORMER 150 MVA DOUBLE WOUND TRANSFORMER NON DIRECTED COOLINGNON DIRECTED COOLING

End user : CHEVRON Indonesia. (Energized 2000)End user : CHEVRON Indonesia. (Energized 2000)

90/150 MVA ONAN/ONAF DOUBLE WOUND TRANSFORMER90/150 MVA ONAN/ONAF DOUBLE WOUND TRANSFORMER

HV : 230 HV : 230 ++ 16 x 0.625% kV OLTC.16 x 0.625% kV OLTC.

IV : 115 kV / LV : 13.8 IV : 115 kV / LV : 13.8 ++ 2 x 2.5% kV DETC2 x 2.5% kV DETC

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End user : End user : TransPowerTransPower New Zealand. (Energized 2005)New Zealand. (Energized 2005)

250 MVA ONAN/ODAF AUTOTRANSFORMER250 MVA ONAN/ODAF AUTOTRANSFORMER

HV : 220 HV : 220 ++ 8 x 1.25% kV OLTC.8 x 1.25% kV OLTC.

IV : 114 kV / LV : 11 IV : 114 kV / LV : 11 ++ 2 x 2.5% kV (capacitive load)2 x 2.5% kV (capacitive load)

250 MVA AUTOTRAFO 250 MVA AUTOTRAFO –– FULLY DIRECTEDFULLY DIRECTED

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Purpose :Purpose :

To directly measure the Hot Spot temperature, To directly measure the Hot Spot temperature, fibrefibre optics can be used to measure temperatures in optics can be used to measure temperatures in cores and tank walls cores and tank walls -- not only the windings of the transformer.not only the windings of the transformer.

Fiber Optic InstallationFiber Optic Installation

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Infra Red Thermal InvestigationInfra Red Thermal InvestigationTypical Infra Red Thermal Check

To avoid local overheatingTo avoid local overheating

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Extendable Plate type Water CoolerExtendable Plate type Water CoolerPossibility to extend the cooler capacity at site to reduce the transformer temperature

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Why is Partial Discharge important for Why is Partial Discharge important for transformer life time ???transformer life time ???

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Partial DischargePartial Discharge

Partial Discharge levelPartial 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.

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Six Categories Of Partial DischargesSix Categories Of Partial Discharges

Partial Discharge Partial Discharge indicates the defects existence prior to indicates the defects existence prior to dielectric breakdowndielectric breakdown.

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.

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Optimized Oil Duct ThicknessOptimized Oil Duct ThicknessThe oil duct thickness has to not only provide reliable cooling The oil duct thickness has to not only provide reliable cooling but has to provide electrical insulation. The diagram shows but has to provide electrical insulation. The diagram shows how a smaller duct provides higher voltage strength per mm.how a smaller duct provides higher voltage strength per mm.

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Equilibrium Of Moisture Content In Oil vs. PaperEquilibrium Of Moisture Content In Oil vs. Paper

Moisture Content In Mineral Oil [ppm weight]

Moi

stur

e C

onte

nt In

Pap

er [%

wei

ght]

The transformer is tested normally at less than 5 ppm moisture content in oil

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Oil Moisture Content Oil Moisture Content vsvs Dielectric StrengthDielectric Strength

Moisture Content In Oil [ppm]

Pow

er F

req.

With

stan

d V

olta

ge [%

]

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Paper Moisture Content Paper Moisture Content vsvs Dielectric StrengthDielectric Strength

Moisture Content In Oil Impregnated Paper [%]

Pow

er F

req.

With

stan

d V

olta

ge [%

]

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Typical Of Low Partial DischargeTypical Of Low Partial Discharge

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Discharging Circle Prior To FlashoverDischarging Circle Prior To Flashover

High Partial Discharge

Insulation Ionization

GassingInsulation weakening

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CONCLUSION FOR MINERAL OIL XMERCONCLUSION FOR MINERAL OIL XMERTemperature limits;Temperature limits;

The temperature limits and the type of overloading at particularThe temperature limits and the type of overloading at particular ambient ambient temperature have to be indicated. temperature have to be indicated. New class A cellulose paper covered conductor immersed in new miNew class A cellulose paper covered conductor immersed in new mineral neral oil will start gassing at hot spot temperature ofoil will start gassing at hot spot temperature of 145145ooC.C.

Cooling system;Cooling system;Fully directed cooling with pump is the most suitable for mediumFully directed cooling with pump is the most suitable for medium & large & large transformer. The directed cooling with no pump can be used for ctransformer. The directed cooling with no pump can be used for cost ost effectivenes consideration on small/medium transformer.effectivenes consideration on small/medium transformer.

Conductor paper ;Conductor paper ;The cellulose paper should have Degree PolymerizationThe cellulose paper should have Degree Polymerization min. 950.min. 950.

Low partial discharge product shall be performanced at factory tLow partial discharge product shall be performanced at factory test;est;=>=> 40 pC up to 120%40 pC up to 120% Voltage for 30 minutes.Voltage for 30 minutes.=> => 75 pC up to 150%75 pC up to 150% Voltage for 30 minutes.Voltage for 30 minutes.=> to monitor the partial discharge at induced level, 1min.=> to monitor the partial discharge at induced level, 1min.

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End User : COMALCO ALUMINIUM SMELTER AUSTRALIA168 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 .

Doubled Capacity On Existing FoundationDoubled Capacity On Existing Foundation

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FUTURE SOLUTIONS ?FUTURE SOLUTIONS ?FUTURE SOLUTIONS ?

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Hybrid Design Hybrid Design

CALENDEREDKRAFT BOARD

NOMEX® T-993Creped NOMEX®

NOMEX® T-410

NOMEX® T-994

Angle Ringsand Caps

Support Washers

Static Rings

Cylinders

ConductorInsulation

Axial & RadialSpacers


PRECOMPRESSEDKRAFT BOARD

Clamping Rings, Blocks


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Hybrid Design Hybrid Design –– Engineering Transformer Engineering Transformer 9797ooC hot spot riseC hot spot rise

Cellulose pressboardCellulose pressboard

Cooling = ONAN in 10 radiatorsCooling = ONAN in 10 radiatorsTop oil rise = 57 KTop oil rise = 57 KAverage HV rise = 62.1 KAverage HV rise = 62.1 KAverage LV rise = 70.1 KAverage LV rise = 70.1 KMeasured HV grad. = 25 KMeasured HV grad. = 25 KMeasured LV grad. = 33 KMeasured LV grad. = 33 KHot spot factor = 1.2Hot spot factor = 1.2

Cellulose insulated lead outsCellulose insulated lead outs

Capacity = 12.5 MVA (ONAN)Voltage = 115 + 1.4 / 21.5 kVBIL HV/LV = 550 / 125 kVVector group = YNd11HV winding = Disc / PI 0.8 / ksp. 2.0LV winding = Disc / PI 0.5 / ksp. 1.5

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CASE STUDY CASE STUDY –– 30 MVA for PG&E30 MVA for PG&E

Built by Pauwels for Pacific Gas & Electric Built by Pauwels for Pacific Gas & Electric

Hybrid designwith same MVA

Cellulose designwith same MVA with same weight

Power (MVA)

Weight (T)

IZ (%)

No load losses(kW)

Load losses(kW)

Temperaturerises (K)

45

44,1

19,1

11,9

752

95

45

57,5

10,0

10

225

65

31,5

44,1

10,0

8

110

65

Cellulose design

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Hybrid Design In Mobile Transformer Hybrid Design In Mobile Transformer Under Substation InstallationUnder Substation Installation

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Hybrid Design In Mobile Transformer Hybrid Design In Mobile Transformer Test DriveTest Drive

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DGA Report DGA Report –– Typical Hybrid designTypical Hybrid designThe gas generation produced by Hybrid transformers The gas generation produced by Hybrid transformers after temperature rise test at PAUWELS factory.after temperature rise test at PAUWELS factory.

Temperature rise test (8 hours) Increment CelluloseGas Symbol

Before After unit in ppm/hour Typical

Hydrogen H2 < 0.8 10.13 ppm 1.27 < 2

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

50 MVA, 16150 MVA, 161--115/13.8115/13.8--34.5 kV, Inert air system, Nitro 10XT oil34.5 kV, Inert air system, Nitro 10XT oil

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Future Future –– Environmental Friendly LiquidEnvironmental Friendly Liquid• Environmental liquid = Enviro-Temp FR3 by COOPER• Inhibited oil = Nitro 10XT by NYNAS

Property Property –– typical valuestypical values Inhibited oilInhibited oil FR3FR3

Antioxidant, phenols 0.08% per Wt

500 hours

25%

Saturated moisture at 25oC 80 ppm 1200 ppm

Temp. rise for unity life time *) 60/65/78 K 80/110/130 K

145oC

-57oC

n.a.

Oxidation stability by 120oC continuous

Biodegradable in 21 days 100%

Flash point 330oC

Pour point -18oC

*) Top oil/Average winding/hot spot rise (+ Hybrid design for FR3)

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Water Saturation of Mineral oil Water Saturation of Mineral oil vsvs FR3FR3

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Liquid Water Absorption versus Time ExposureLiquid Water Absorption versus Time Exposure

Water Absorption of Dielectric FluidsExposed to Ambient Air (1 of 2)

Exposure Time (hrs)

0 500 1000 1500 2000 2500 3000 3500

Abs

olut

e W

ater

Con

tent

(ppm

)

0

100

200

300

400

500

600

conventional transformer oilEnvirotemp FR3 fluid

100% Saturation = 100% Saturation = FR3, 1200 FR3, 1200 ppmppmMineral Oil, 80 Mineral Oil, 80 ppmppm

Exposure Time (hrs)

0 500 1000 1500 2000 2500 3000 3500

Rel

ativ

e W

ater

Con

tent

(% s

atur

atio

n)

0

20

40

60

80

100

Water Absorption of Dielectric FluidsExposed to Ambient Air (2 of 2)

conventional transformer oilEnvirotemp FR3 fluid

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Dielectric Strength versus Water Content

Water Content (ppm)

0 100 200 300 400 500 600

D 1

816

Die

lect

ric B

reak

dow

n (k

V)

0

10

20

30

40

50

60

70

80

Envirotemp FR3 fluidconventional transformer oil

Liquid Dielectric Strength vs. Water ContentLiquid Dielectric Strength vs. Water Content

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Partial Discharge Of FR3 Filled Partial Discharge Of FR3 Filled TransformerTransformer

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Prototype transformer filled with FR3Prototype transformer filled with FR3

12/17 MVA, 33kV,ONAN/ONAF + provision for future ODAF 12/17 MVA, 33kV,ONAN/ONAF + provision for future ODAF Measured PD = Measured PD = 25 25 pCpC max. at induced voltage level.max. at induced voltage level.

Liquid Main tank = Liquid Main tank = EnviroEnviro Temp Temp -- FR3 FR3 (Hi-Temp natural – ester based 100% biodegradable)

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Low partial discharge product ;Low partial discharge product ;Assists to increase a units life from overvoltage spikes Assists to increase a units life from overvoltage spikes and prolongs oil qualityand prolongs oil quality

• Typical guaranteed partial discharge ;75 pC75 pC at 150% Un, IEC 60076 500 pC at 150% Um40 pC40 pC at 120% Un, IEC 60076 100 pC at 110% Um

• Typical achievement , by rating voltage = 220 kV (950 kVp BIL);14 pC at 150% voltage.27 pC at 200% voltage.

Dirrected cooling path ;Dirrected cooling path ;Assists life time expectation under overloading Assists life time expectation under overloading

conditions and suitable for Low noise requirement.conditions and suitable for Low noise requirement.Compact design, safety and enviromental friendly;Compact design, safety and enviromental friendly;

Usage Hybrid design and Vegetable liquid to minimize Usage Hybrid design and Vegetable liquid to minimize the land spacethe land space required, less flammable risk and required, less flammable risk and enviromental friendly unit.enviromental friendly unit.


Page 92 of 94

APPENDIX C

EPECENTRE ELECTRIC POWER R&D CAPABILITY

Power Systems

Reliability

Alternative Power

Generation

Energy Efficient Generation & Distribution Demand Side

Management

HV Testing

Power Transformers

Energy Modelling

www.epecentre.ac.nz

New ZealandNew Zealand’’s s Centre of Centre of Excellence for Excellence for Power Power EngineeringEngineering

SystemStudies

Electric Power R&D Programme

Supporting Industry RSupporting Industry R&D needs for NZD needs for NZ’’s Energy Futures Energy Future……

Power Quality

Renewable Energy

Short-term projects in specialist areas (see overleaf); customised technical workshops &

training; design & testing; technical advise and support.

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.

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.

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.

Orion, Transpower NZ, Meridian Energy, Vector, Enermet, ElectraNet SA, Metrix, ACCG, Antarctica NZ, Canterbury TX, Pearson Innovations, CAE NZ...

Launched New ZealandLaunched New Zealand’’s first s first collaborative industrycollaborative industry--academia Racademia R&&D D

Programme for power in 2005Programme for power in 2005……

www.epecentre.ac.nzwww.epecentre.ac.nz

Electric Power Engineering Centre (EPECentre)University of Canterbury,

Private Bag 4800, Christchurch, New ZealandTel: +64 21 1144 330

Email: [email protected]

About Us

Our People

Our Facilities

Our Services

our industry partners:our industry partners:

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