CAN/GSA - C88-M90 (Reaffirmed 1994) Power Transformers and Reactors Electrical Power Systems and Equipment A National Standard of Canada Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.(Reaffirmed 2009)The Canadian Standards Association (CSA), under whose auspices thisNational Standard has been pro- duced, wascharteredin1919and accredited by the Standards Council of Canada to the NationalStandards system in1973.It isa not-for-profit, nonstatutory, voluntary membership association engaged in stan- dards development and certification activities. CSA standards reflect a national consensusof produc- ers and users including manufacturers,consumers, retailers, unionsand professionalorganizations, and governmental agencies. The standards are used widely by industry and commerce and often adoptedby mu- nicipal,provincial, and federal governments intheir regulations, particularly inthe fields of health,safety, building and construction, and the environment. Individuals,companies, and associations across Can- ada indicate their support for CSA'sstandards develop- ment by volunteering theirtimeandskillstoCSA Committee work and supporting the Association's ob- jectivesthroughsustaining memberships. The more than 7000 committee volunteers and the 2000 sustain- ing memberships together form CSA's total membership from which its Directors are chosen. Sustaining mem- berships represent a major source of incomefor CSA's standards development activities. TheAssociation offers certification and testing services in support of andasanextensionto itsstandards development activities.To ensure the integrity of its certification process, the Association regularly and con- tinually audits and inspects products that bearthe CSA Mark. In addition to its head office and laboratory complex in Rexdale (Toronto), CSA has regional branch offices in major centres across Canada and inspection and testing agencies in eight countries.Since 1919, the Association has developed the necessary expertise to meet its cor- porate mission:CSA is an independent service organi- zation whose mission is to provide an open and effective forum for activitIes facilitating the exchange of goods and services through the use of standards, certification and related servicesto meet national and international needs. For further informationon CSA services,write to Canadian Standards Association 178 Rexdale Boulevard Rexdale (Toronto),Ontario, Canada M9W 1R3 The Standards Council of Canada is the coordinat- ing body of the NationalStandards system, a federation of independent, autonomous organizations working to- wardsthe further development and improvement of voluntary standardizationin the national interest. The principal objects of the Council are to foster and promote voluntary standardizationas a means of ad- vancing the national economy,benefiting the health, safety, and welfare of the public, assisting and protect- ing the consumer, facilitating domesticand interna- tional trade, and furthering international cooperation in the field of standards. A National Standardof Canada is a standard which has been approved by the Standards Council of Canada and one whichreflects a reasonable agreement among the views of a number of capable individualswhose collective interests provide to the greatest practicable extent a balance of representation of producers, users, consumers, and others with relevantinterests, as may be appropriate to the subject in hand.It normally is a standard which is capable of making a significant and timely contribution to the national interest. Approval of a standard as a National Standardof Canada indicates that a standard conforms to the cri- teriaand procedures established by the Standards Councilof Canada. Approval does not refer tothe technicalcontent of the standard; this remainsthe continuing responsibility of the accreditedstandards- writing organization. Those who have a need to apply standards are encour- aged to use National Standards of Canada whenever practicable. Thesestandardsare subject to periodic review;therefore, usersarecautionedto obtain the latest editionfrom the organizationpreparing the stan- dard. The responsibility for approving National Standards of Canada rests with the Standards Council of Canada 45 O'Connor Street Suite 1200 Ottawa, Ontario K/P 6N7 National Standards of Canada are available in English or in French Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.General Instruction No. 2 CAN/GSA-C88-M90 November1990 CSA Standard CAN/CSA-C88-M90,Power Transformers and Reactors,was published in August 1990;it consisted of 91 pages, each of which was dated August 1990. Errata to Tabte 2 and Figures 4, 5, and 6 have been incorporated (and identified by a vertical line in the margin) in the attached replacement pages. CSA Standard CAN/CSA-C88-M90now consists of the following pages: 332,3576,7982, 8591dated August 1990; 33, 34, 77, 78, 83, and 84 dated November1990. These replacement pages are to be inserted into your copy of the Standard; the pages replaced shouldbe kept for reference. Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.Note:In forced-directed flow, the oilisdirected from the coolers into the inletducts of all or some windings of the transformer, so as to pump the oil through the windings. 6.4 Designations and Order of Symbols The designations and order of symbols shall be as shown in Table 1. Table 1 Designations and Order of Symbols 1st Letter2nd Letter3rd Letter4th Letter Internal coolingType of internalExternal coolingType of external mediumcirculationmediumcirculation 6.5Standard Type Designations The standard types of transformers with their designations shall be asfollows: Standard Type Designation (a) Oilfilled natural cooling ONAN; (b) Oilfilled water cooling ONWF; (c) Oilfilled forcedair cooling ONAF; (d) Oilfilled forcedoil water cooling OFWF; (e) Oilfilled forcedoil forced-air cooling OFAF; (f) Oilfilled forceddirected oil forcedair coolingODAF; (g) Oilfilled forcedoil natural cooling OFAN; (h) Flameretardant liquidfilled natural cooling LNAN; (i) Flameretardant liquidfilled water cooling LNWF; (j) Flameretardant liquidfilled forcedair cooling LNAF; (k) Flameretardant liquidfilled forcedliquid water cooling LFWF; (1) Flameretardant liquidfilled forcedliquid forcedair cooling LFAF; (m) Flameretardant liquidfilled forcedliquid natural cooling LFAN. 6.6 Type Designation for More Than One Method of Cooling Where the apparatus has more than one method of cooling, the type designations for all methods shallbe stated, separated from each other by an oblique (/). In all cases of multiple cooling, the power for each stage of cooling shall be designated. Note: Typical examples are (a)ONAN/ONAF 30/40 MVA--an oil-filled transformer having a naturally cooled (ONAN) rating of 30 MV'A and a forced-air-cooled (ONAF) rating of 40 MVA; (b)ONAN/ONAF/ONAF 30/40/50 MV'A--a transformer having a naturally cooled (ONAN) rating of 30 MV'A, a forced-air-cooled (ONAF)rating of 40MVA achieved by operating only part of the fans, and an increased forcedair-cooled (ONAF) rating of 50 MV'A when allthe fans are operating; (c)ONAN/ONAF/OFAF 30/40/50 MVA--a transformer having a naturally cooled (ONAN) rating of 30 MV'A, a forced-air-cooled(ONAF) rating CAN/CSAC88M90 - November1990 Page 33 (Replaces p.33,August 1990) Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.of 40 MV'A with only the fansoperating, and aforced-oil forced- air-cooled (OFAF) rating of 50 MVA with both fans and oil pumps operating; and (d)ONAN/ONAF/ODAF 30/40/50 MV'A--a transformer having a naturally cooled (ONAN) rating of 30 MVA, a forced-air-cooled (ONAF) rating of 40 MVA with only the fans operating, and aforceddirected oil- forced-air-cooled (ODAF) rating of 50 MVA with bothfans and pumps operating. For ODAF theinstruction bookfor the transformer shallidentify windings with and without forceddirected flow cooling. 7.Ratings 7.1Preferred MVA Ratings The preferred MVA ratings are stated in Table 2 for singlephase and threephase twowinding transformers, multiwinding and auto transformers when only two setsof terminals are brought out of the tank, and shuntreactors (for basis of Mvar rating see Clause 20.1). Table 2 Preferred MV'A Ratings for Transformers Preferred ratings in MVA 0.5550500 0.676.6766.7667 0.838.3383.3833 110100 1.2512.5125 Singlephase 1.6716.7167 220 200 2.525250 3.3333.3333 440400 1.5151501500 2202002000 2.525250 330300 3.7537.5375 Threephase 5 6 7.5 10 12 50 60 75 100 120 500 600 750 1000 1200 Note:For multiple-rated transformers, the preferred MVA rating for the ONAN rating is according to Table 2; for the first stage of forced cooling (ONAF)the preferred increase is 33, and for the second stage of forced cooling (ONAF/ONAF or OFAF)the preferred CAN/CSAC88-M90 - November1990 - Page 34 (Replaces p. 34, August 1990)Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.Type (B) Series Winding in Input (Constant Load Voltage LTC Compensates for Varying Source Voltage) Notes: (1) A booster transformer may be used where the linecurrent exceeds theload tapchanger capability. (2) 10% voltage regulation is shown in this example. (3)Arrangements shown are for singlephase transformers. Figure 4 Voltage LimitsSeriesVoltage Regulators CAN/CSAC88-M90 - November1990 - Page 77 (Replacesp.77, August 1990) SourceLoadSource VoltageVoltageVoltage Load Vollage 120% Maximum Raise Variationwith Positionof Load-Tap Changer MaximumLower Source Source p Fixed turn windingSeries winding Load 4--o Type(A) Series Winding in Output (Constant Source Voltage LTC Varies Load Voltage) Series winding Load Fixed turn winding Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.22.7 Rating Plate Regulators shallbe provided with rating plates in accordance with Clause 17, except that (a) the rated nominal input and outputvoltages shall be shown for at leastthosetapchanger positions that represent the minimum, neutral,and maximum voltages; (b) the rated input and output currents shallbe shownfor all voltage positions as required in Clause 22.7(a); and (c)impedance voltages shallbe shownfor the positions required by Clause 22.7(a)(see Clause 22.4.4). 22.8Mechanical Features and Accessories 22.8.1Standard Mechanical Features and Accessories The standard mechanical features and accessories listedin Clause 15.1,with the following additions, shallbe standard and supplied with the regulator: (a) A driving motor shall be supplied for operating the LTC switch.If singlephase, it shallbe without centrifugal switch. (b) A handcrank or handwheel for manual operation ofthe driving mechanism shall be supplied. If a handcrank or spoketype of handwheel is provided, it shallbe interlocked to prevent operation by the motor while the crank or spoketype hand-wheel is engaged. A place for storing the handcrank or handwheel, if detachable, shallbe provided. (c)Mechanically operated electric limitswitches and mechanical stops shallbe provided on the drive mechanism to prevent travel beyond the extreme LTC switch positions. (d) A positionindicating device with drag handsshallbe supplied. Thisindicator shall be labelled, with 0 as the neutral position.Tap positions that give a progressively lowerload voltage (sourcevoltage being considered fixed) shallbe labelled as 1L,2L,3L, etc. Tap positions that give a progressively raised load voltage (source voltage being considered fixed) shall be labelled as1R,2R,3R, etc.If several positions correspond to the same load voltage orturnsratio,they shallbe noted by the numberletter combination but followed by A,B,C, etc (eg, a tap changer with three neutral positions shallbe labelled OA,OB, OC). For automatic or manual operation, the control system shallbe such that the tap changer shall stop on only one of these positions. (e) A local control switch and provision for adding a remote control switch shall be supplied. (f) Means of filling, draining, venting, and liquid level indication shall be supplied foreach separate liquid chamber. Liquiddrain valve for diverter shallbe supplied when applicable. (g) A weatherproof control cabinet shall be mounted on the main tankand provided with means to prevent condensation. (h) A controlpower isolating switch shallbe supplied. 22.8.2Optional Accessories Optional accessories may be supplied if specified.(See Clause 24.9.2.) CAN/CSAC88M90 November1990 Page 78 (Replacesp.78, August 1990)Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.ii p Notes: (1)Type Ais usedwhere the major variation of voltage is required atthelow-voltage terminalandthenormal high-voltage variationisacceptable onafixedturnwinding. (2)Type Bis used where the major variation of voltage is required at the high-voltage terminal and the normal low-voltage variation is acceptable on a fixed turn winding. (3)Arrangements shown are for singlephase transformers. Figure 5 LTC Transformer Windings CAN/CSAC88M90 November1990 Page 83 (Replaces p.83,August 1990) HVLVHV LV J Type B LTCin HIT Winding Type A LTCin LV Winding Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.24.3 Autotransformers Three basicformsof LTC windings are considered.Type C has the LTC in the serieswinding.Type D has the LTC in an auto-point winding, and Type E hasthe LTC in the neutral.(See Figure 6.) Booster transformer circuits may be used. HV HV LV LV 4C Type CType DType E LTC in Series LTC at Autopoint LTC in Neutral Notes: (1)Type C is used where the major variation of voltage is required atthe high-voltage terminaland the normal low-voltage variation is acceptable on afixed turnwinding. (2)Type D is used where the major variation of voltage is required at the low-voltage terminal and the normal high-voltage variation is acceptable on a fixed turn winding. (3)Type Fl varies the effective turns of both the high voltage and the low voltage, but has greater proportional effect on the low voltage. It is therefore similar to Type D,except that the magnetic induction willvary with tap-changer position.(A tertiary or other winding will have avoltage variation as a result of the varying induction, unless other means are used to prevent such voltage variation.) (4)Arrangements shown arefor single-phase transformers. Figure 6 LTC Autotransformer Windings CAN/CSAC88M90 - November1990 Page 84 (Replacesp.84,August 1990) HV Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.General Instruction No.1 CAN/CSA - C88-M90 August 1990 GSA Standard GAN/GSA-G88-M90,Power Transformersand Reactors, consists of 91 pages,each dated August 1990. This Standard, like all GSA Standards, is subject to periodic review, and amendments in the form of rep'acement pages may be issued from time to time; such pages will be mailed automatically to those purchasers who complete and return the attached card.* Some Standards require frequent revision between editions, whereas others require none at all.It is planned to issue new editions of the Standard, regardless of the amount of revision, at intervals not greater than 5 years.Except in unusual circumstances, replacement pages will not be issued during the last year of that edition. * This card will appear with GeneralInstructionNo. 1 only. Atthough any reptacement pages that have beenissued will be sold with the Standard, it is for the purchaser to insert them where they apply. The responsibility for ensuring that his or her copy is comptete rests with the holder of the Standard, who should, for the sake of reference, retain those pages which have been replaced. Note: A GeneralInstructionsheet will accompanyreplacementpages each time they are issued and will list the latest date of each page of the Standard. Cut along dotted line Name Organization Address City Prov./State CSAStandard Postal/Zip Code_________ CAN/CSAC88M9O Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.Canadian Standards Association Consolidated Mailing List 1 78Rexdale Boulevard Etobicoke, Ontario Canada M9W 1 R3 Place Stamp Here Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.National Standard of CanadaCA N/CSA - C88-M90 Power Transformersand Reactors Preparedby Canadian Standards Association Approvedby Standards Council of Canada 1SSN 0317-5669 Published/n August 1990 by Canadian Standards Association 178 Rexdale Boulevard Rexdale (Toronto), Ontario, Canada M9W 1R3 Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.TechnicalEditor:John Davis ManagingEditor:Bernard Kelly Canadian Standards Association 1990 All rights reserved.No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior permission of the publisher. Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.Contents Technical Committee on Power Transformers7 Preface9 1. Scope 11 2.Reference Publications11 3.Service Conditions and Loading 13 3.1Intended Use13 3.2Usual Service Conditions14 3.3Unusual Service Conditions14 3.4 Loading Beyond Rated MVA15 3.5LowAmbient Temperature Load Capability 16 4.Definitions16 5.Terminal Markings, Polarity, and Angular Displacement 26 5.1General26 5.2Identification of Windings 27 5.3 Marking of Terminals27 5.4Order of Numbering Terminals28 5.4.1 SinglePhase Transformers28 5.4.2ThreePhase Transformers28 5.5Location of External Terminals and Polarity of SinglePhase Transformers29 5.5.1Location of External Terminals29 5.5.2 Polarity 29 5.6Location of External Terminals and Angular Displacement of ThreePhase Transformers29 5.6.1Location of External Terminals29 5.6.2 Angular Displacement 30 5.7Terminal Markings forSeriesVoltage Regulators 32 6. Types Based on Cooling Methods32 6.1General32 6.2 Cooling Medium32 6.2.1Internal Cooling Medium32 6.2.2External Cooling Medium32 6.3 Type of Circulation33 6.4 Designations and Order of Symbols 33 6.5Standard Type Designations 33 6.6 Type Designation for More than One Method of Cooling 33 7. Ratings 34 7.1Preferred MV'A Ratings 34 7.2Basis of MVA Rating 35 7.3Basis of Voltage Rating 36 8. voltage Taps for Deenergized Operation 36 CAN/CSAC88-M90 August 1990 - Page 3Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.9.Temperature Rise37 9.1Conditions Under Which TemperatureRise Limits Apply 37 9.2Limitsof Temperature Rise for Continuous Operation 37 9.3Winding Conductor Insulation37 10.ShortCircuit Characteristics38 10.1General38 10.2ShortCircuit Current Magnitude 38 10.2.1All Transformers38 10.2.2TwoWinding Transformers39 10.2.3Autotransformers and Multiwinding Transformers40 10.2.4SeriesVoltage Regulators 40 10.3ShortCircuit Current Duration41 10.4Limits of Temperature Rise41 10.5Transformer Terminal and System Conditions41 11.Insulation Levels and Clearances in Air41 11.1Selection of Insulation Levels for Line Ends of Windings 41 11.2Selection of Insulation Levels for Neutral Ends of Windings 41 11.3Selection of Bushings 43 11.4External Clearances in Air44 12. Stabilizing Windings 45 13.Sound Levels46 14.Tolerances50 15.Mechanical Features and Accessories51 15.1Standard Mechanical Features and Accessories51 15.1.1General51 15.1.2 Liquid Preservation System 51 15.1.3Transformer Tank51 15.1.4 Tap Changer for Deenergized Operation 51 15.1.5Breather52 15.1.6 Moving Facilities52 15.1.7TankAccess52 15.1.8 Emergency PressureRelief Device52 15.1.9 Marking 52 15.1.10 Liquid Level Indicator52 15.1.11 Liquid Temperature Indicator52 15.1.12 winding Temperature Indicator53 15.1.13Automatic Control forFans53 15.1.14Automatic Control for Pumps 53 15.1.15 Liquid Drain Valve53 15.1.16 Liquid Sampling Valve53 15.1.17 Liquid Treatment Connections53 15.1.18Radiator Valves53 15.1.19water Piping 53 15.1.20 Insulating Liquid Piping 54 15.1.21 Grounding 54 15.1.22Control Cabinets54 15.1.23Instruction Manual54 15.1.24Vacuum/Pressure Gauge 54 15.1.25Sudden Pressure Relay 54 15.1.26Gas Detector Relay 55 CAN/CSAC88M90 August 1990 Page 4 Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.15.2 Optional Accessories55 15.3Preferred Voltages for Auxiliaries and Accessories55 16.Tests56 16.1Method of Making Tests56 16.2Test Report 56 16.3 Summary of Teststo be Performed56 16.4Dielectric Tests57 16.4.1General57 16.4.2 Applied Potential Test58 16.4.3Induced Potential Test58 16.4.4 LightningImpulse Tests60 16.4.5 Switching Impulse Tests63 16.5Lossand Impedance Tests63 16.6Mechanical Tests64 16.7Core Insulation Tests64 16.8ShortCircuit Test64 16.9SoundLevel Test64 17. Rating Plate65 18.Instruction Manual70 19.Finish71 20.ShuntReactors71 20.1Basis of Mvar Rating 71 20.2 Operation Above Rated Voltage 71 20.3 Linearity 71 20.4Tests71 20.4.1General71 20.4.2Routine Tests71 20.4.3 Applied Potential Tests72 20.4.4TurntoTurn Potential Test72 20.4.5 Type Tests73 20.4.6Other Tests73 21. Grounding Transformers73 21.1Basis of Rating 73 21.2Limits of Winding Temperature 73 21.3Limits of Tank Temperature 74 21.4Tolerance for Impedance 74 21.5Mechanical Strength 74 21.6Accessories74 21.7Tests74 22. SeriesVoltageRegulators 74 22.1General74 22.2Basis of Rating 74 22.3 Operating Voltage Limits75 22.4Losses and Impedance 75 22.4.1Tolerances for Losses and Impedance 75 22.4.2Excitation Loss75 22.4.3LoadLoss75 22.4.4 Impedance 76 CAN/CSAC88-M90 August 1990 Page 5 Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.22.4.5Normal Conditions forthe Determination of Lossesand Exciting Current76 22.5Short Circuits76 22.6Diagram of Connections76 22.7Rating Plate78 22.8Mechanical Features and Accessories78 22.8.1Standard Mechanical Features and Accessories78 22.8.2Optional Accessories78 22.9 Accuracy Classes79 22.10Errors for Accuracy Determination80 22.11Compensator Marking Deviation80 22.12TestTerminals80 22.13Tests81 22.14Sound Levels81 23.Phaseshifting Transformers81 24.Transformers and Autotransformers with LoadTapchanging (LTC) 81 24.1General81 24.2Multiwinding Transformers82 24.3Autotransformers84 24.4Alternative TapChanger Locations85 24.5 Voltage_Regulating Range 85 24.6ShortCircuit Characteristics85 24.7Low Ambient Temperature Capability 85 24.8 Paralleling 85 24.9Controls and Indicators85 24.10Mechanical Features and Accessories86 24.11 Rating Plate86 Appendices AInformation Required with Enquiry and Order88 BMechanical Strength ofTransformerstoWithstandExternalShort CircuitCurrents90 CAN/CSAC88M90 August 1990 Page 6Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.Technical Committee on Power Transformers G.E. Woolley Ontario Hydro, Chairman Toronto Representing Canadian Electrical Association J. AubinHydro-Qubec, Var ennes Representing Canadian Electrical Association T.A. Bickley Transelectrix Technology Inc., Guelph, Ontario M.N. Campbell New Brunswick Electric Power Commiss ion, Fredericton Representing Canadian Electrical Association F. DavidFederal Pioneer Limited, Winnipeg, Manitoba T. Freyhult ABB Inc., Varennes, Quebec L.M.Nicholas Moloney Electric Corporation, Toronto, Ontario D.D. PercoTranselectrix Technology Inc., Guelph, Ontario Representing Electrical and Electronic Manufacturers Association of Canada G.PolovickBritish Columbia Hydro, Vancouver Representing Canadian Electrical Association R.SeoniAcres International Limited, Niagara Falls, Ontario D.N.SharmaNova Scotia Power Corporation, Halifax Representing Canadian Electrical Association R.G.ShurtleffCity of Kingston Public Utilities Corniniss ion, Kingston, Ontario R.A.VeitchNEI Canada Limited, St. Catharines, Ontario CAN/CSAC88M90 August 1990 Page 7Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.G.WeeksAlcan Smelters and Chemicals, Jonquire, Qubec J.DavisCanadian Standards Association,Standards Rexdale, Ontario Administrator, Nonvoting CAN/CSAC88M90 August 1990 Page 8Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.Preface Thisis the fourthedition of CSA Standard C88,Power Transformers and Reactors.It supersedes the previous editions published in 1947,1968, and 1979. Thisrevision of theStandard includes several significant changes including general reorganization and rearrangement.Major changes include the addition of external airclearances,the elimination of baseMVA limitsfor induced,applied, and impulse tests, and the elimination of chopped wave tests.A requirement for measurements of apparent charge in addition to RIV measurements has been added fortransformers over245 kV.ThisStandard recognizes atransformerwith forced directed oil flowand permits an average winding temperature riseof 70C forthesetransformers. A requirement for thermally upgraded paper has been added.Clauses referring to prefault operating voltage and external shortcircuit withstand requirements havebeen clarified. ThisStandard was prepared by the Technical Committee on Power Transformers underthe jurisdiction ofthe Standards Steering Committee on Electrical Engineering, and was formally approved by these Committees.Ithas been approved as aNational Standard by the Standards Council of Canada. August 1990 Notes: (1) Use of the masculine gender in thisStandard is not meant to exclude the feminine gender when applied to persons.Similarly, use of the singular does not exclude the plural(and viceversa) whenthe sense allows. (2)Although the intended primary application of this Standard is stated in its Scope, it is important to note thatit remains the responsibility of the user of the Standard to judge its suitability for his particular purpose. (3) CSA Standards are subject to periodic review, and suggestions for their improvement willbe referred tothe appropriate comrnit tee. (4) All enquiries regarding this Standard, including requests for interpretation, should be addressed to Canadian Standards Association,Standards Division, 178 Rexdale Boulevard, Rexdale, Ontario M9W lR3. Requests for interpretation should (a)definethe problem, making reference tothe specific clause, and,whereappropriate, include an illustrative sketch; (b)provide an explanation of circumstances surrounding the actual field condition; and (c)be phrased where possible to permit a specific "yes" or "no" answer. Interpretations are published in CSA Information Update. For subscription details and a free sample copy, write to CSA Sales Promotions or telephone (416)747-4116. CAN/CSAC88M90 August 1990 Page 9 Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.CAN/CSAC88M90 August 1990 Page 10Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.CAN/CSAC8 8M90 Power Transformers and Reactors 1. Scope 1.1 ThisStandard,except asnoted inClause1.2,applies to all liquidfilled transformers, autotransformers, booster transformers, loadtapchanging transformers, grounding transformers, phase shifting transformers,seriesvoltage regulators, and shunt reactors. Notes: (1) The term"transformer(s)" in this Standard refers tothe overall unit and not just to the electrical components implied by the definition. (2) In general this Standard is written in reference totwo winding transformers,although many requirements willbe recognized to be common to multiwinding transformers,autotransformers, load tapchanging transformers, shunt reactors,and seriesvoltage regulators. Wherethereare special requirements for these(other) transformers, there are sections contained herein specifically addressed to them. 1.2 This Standard doesnot apply to the following: (a) distribution transformers (CSA Standard C2, Single-Phase and Three-Phase Distribution Transformers,Types ONAN and LNAN); (b) instrument transformers (CSA Standard C13,Instrument Transformers); (c)drytype transformers (CSA Standard C9, Dry-Type Transformers); (d)padmounted transformers (CSA Standard C227Seriesof Standards); (e) submersible transformers (CSA Standard C301Seriesof Standards); (f)threephase network transformers (CSA Standard C199, Three- PhaseNetwork Transformers); (g) rectifiertransformers, welding transformers, furnace transformers,starting transformers, testing transformers, or currentlimiting reactors. Note:In the above list the pertinent CSA Standard number has been noted wheresuch exists.Where no CSA Standard exists, this Standard may be used insofar as it applies. 2.Reference Publications 2.1 Where reference ismade to other publications, such references shallbe considered to referto the latestedition and any amendments published thereto. CAN/CSAC88-M90 August 1990 Page 11 Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.CSA Standards C501976, Insulating Oil, Electrical for Transformers and Switches; CAN3C3081985, The Principles and Practice of Insulation Coordination. ANSI*Standard Si. 41983, Specification for Sound Level Meters. ANSI/IEEEt Standards 321972,CR1984) Requirements, Terminology and Test Procedures for Neutral Grounding Devices; C57.12.OO1987, General Requirements for Liquid-Irrirnersed Distribution, Power, and Regulating Transformers; C57.12.801978, CR1986) Terminology for Power and Distribution Transformers; C57.12.901987, Test Code for Liquid Immersed Distribution, Power, and Regulating Transformers and Guide for Short-Circuit Testing of Distribution and Power Transformers; C57.151986, Requirements, Terminology, and TestCodefor Step-Voltage and Induction-Voltage Regulators; C57 .211981, Requirements,Terminology, and TestCodefor Shunt Reactors; C57.921981, Guidefor Loading MineralOil-Immersed Power Transformersuptoand Including 100MVA with 55Cor 65CWinding Rise; C57 .981986, Guide for Transformer Impulse Tests; C57 .1131988, Guide for Partial Discharge Measurement in Liquid-Filled Power Transformers and Shunt Reactors; C57 .1161989 Guide for Transformers Directly Connected to Generators. CEA# Publications Guide for Dissolved Gases in Oil Analysis for Transformers and Reactors During Factory Tests(Revision 11989); Power Transformer Test Report Format (1989). CAN/CSAC88M90 August 1990 Page 12Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.EEMACStandards 3611987, Insulating Mineral Oilfor New Electrical Apparatus; GL131989, PowerTransformer and Reactor Bushings; L1011969, Load-Tap--Changing Paralleling Schemes; L1311976, Dielectric Tests and TestProcedures for Power Transformers; L1411976, Liquid LevelIndicators for Power Transformers; L1511976, Temperature Indicators for Power Transformers; Y121979, Performance Specification for Finishing Systems for Outdoor Electrical Equipment. IEEE** Publication 7561984 (expected tobecome ANSIC57.115), Loading Mineral-OilImmersed Power Transformers Rated in Excess of 100 MVA. IECtt Publications 761976, Power Transformers, Part 4,Tappings and Connections; 2141989, OnLoadTap-Changers; 6161989, Terminaland Tapping Markings for Power Transformers. *erjcan NationalStandards Institute tAmerican NationalStandards Institute/Institute of Electrical and Electronics Engineers +Canadian ElectricalAssociation Electrical and Electronic Manufacturers Association of Canada **Institute of Electrical and Electronics Engineers ttlnternational Electro technical Commission 3.Service Conditions and Loading 3.1Intended Use All liquidfilled power transformers and reactors shall be suitable for outdoor service unless specified for indoor service. CAN/CSAC88--M90 August 1990 Page 13 Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.3.2Usual Service Conditions 3.2.1 All transformers and reactorsshall be suitable for operation under the following conditions: (a) Altitudea height above sealevel not exceeding 1000m. Note:For higher altitudes, see Clauses 3.3.1and 3.3.3. (b)Temperature of Cooling Mediumfor watercooled apparatus, cooling waterat a temperature not exceeding 25Catthe inlet;for aircooled apparatus, air at a temperature never exceeding 40C, and (i) never below 50C in the caseof outdoor transformers; or (ii) never below 5C in the caseofindoortransformers. Inaddition,for aircooled apparatus, an air temperature never exceeding the following values: (iii) 30C average in any one day; (iv) 20C average in any one year. Note:For higher temperatures, see Clause 3.32. (c) Wave Shape of Supply Voltage-a supply voltage of which the wave shape is approximately sinusoidal. (d)Synimetry of Polyphase Supply Voltages--for polyphase transformers, supply voltages thatare approximately symmetrical. 3.2.2 All loadtapchanging (LTC)equipment must be suitable for operation down to 25C.For lowertemperature requirements, agreement between the manufacturer and the purchaser isessential asto the requirement for heating devices or lockout devices (or both,when required). The lockout device shallbe actuated by a sensor in the diverter switchoil. 3.3Unusual Service Conditions The conditions described in Clauses 3.3.1to 3.3.5 may affect performance and should receive special consideration. 3.3.1Reduced Temperature Rises for Transformers Designed for High Altitudes Unless otherwise agreed upon between the manufacturer and the purchaser, for aircooled transformers designed for operation atan altitude higher than 1000 m,buttested at normal altitudes, the limits of temperature rise arereduced by the following amounts for each 500 m by which theintended working altitude exceeds 1000m: (a)liquidfilled, naturalaircooled transformers, 2.0%; (b)liquidfilled, forcedair--cooled transformers, 3.0%. 3.3.2Reduced Temperature Rises for Transformers Designed for HighCooling Medium Temperatures or Special AirCooling Conditions If the transformer is designed for service where the temperature of the cooling air exceeds one of the maximum values shown in Clause 3.2.1(b)by no more than 10C,the allowable temperature risesfor the windings, core(s), and liquid shallbereduced. Ifthe base rating is 10 MV'A or greater, thereduction willbe by the same amount as the cooling air exceeds the limit.For smaller ratings, the allowable temperature risesshall bereduced (a)by 5C if theexcess temperature islessthan or equal to 5C; (b)by 10Cif theexcess temperature is greater than5C and less CAN/CSAC88M90 August 1990 Page 14Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.thanor equal to 10C. Where, for aircooled transformers the excesstemperature of the cooling air exceeds 10Cor, for watercooled transformers the temperature ofthe cooling water exceeds 25C,the allowable temperature rises require an agreement between the manufacturer and the purchaser. Any sitecondition that may eitherimpose restrictionson the air cooling or produce highambient air temperatures should be specified by the purchaser. 3.3.3Increased Air Clearance for Transformers Designed for High Altitudes The puncture strength and the flashover voltage in the immersion medium are not affected by altitude.In orderto ensure that the external withstand voltages are notreduced at altitudes exceeding 1000m,the air clearance normally required must be increased by a suitable amount.The amount by which theinsulation level,on whichthe airclearance isbased,should be increased is,for general guidance, 1.0% for each 100 m in excessof 1000 m above sea level. Example: Altitude ofinstallation: 2800 m. Increase in insulation level required(2810) x1.0%18%. Note:The air density at high altitudes is lower thanat sea level.The dielectric strength of theair is thus reduced and air clearances that are adequate at altitudes not exceeding 1000 m may be insufficient at higher altitudes. (See EEMAC Standard GL1-3, PowerTransformer and Reactor Bushings.) 3.3.4Other Unusual Service Conditions The following conditions may affect thetransformer performance and should receive special consideration: (a)exposure to damaging fumesor vapours, explosive mixtures of dustsor gases, steam,salt spray, excessive moisture or dripping water, abnormal vibration, shocksor tilting, unusual storage or transportation conditions, or unusual space limitations; (b)frequency of LTC operation, difficulty of maintenance, harmonic content, unbalanced voltage,special insulation requirements; (c) excitation exceeding 110%ofratedvolts per hertz; (d)planned shortcircuits as part of regular operating or relaying practice; (e)earthquake. 3.3.5Heat Radiation Properties of Paint Finish Metallic flake paints suchas aluminum,zinc,etc, have radiation properties thatincrease the temperature riseof transformers except in direct sunlight. Particular note shouldbe made of a paint's radiation properties when a transformer is painted inthe field. 3.4 Loading Beyond Rated MVA The purchaser is strongly advised to address any needsfor transformer loading capability beyond nameplate rating atthe time of specification for purchase, otherwise it can be laterfound that ancillary equipment,winding leads,internal metallic parts heated CAN/CSAC88-M90 August 1990 Page 15Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.by leakage flux,etc,may restrict loading levelsto below those inherentinthe windings. Reference should be made tothe ANSI/IEEE guide C57.92 for transformers with a maximum nameplate rating up to and including 100 MVA, andIEEE 756forthosewith a rating over100 MVA, for afull description of risksand limitationsof loading beyond nameplate rating. 3.4.1Generator StepUp Transformer Loading Capability Asthe requirement for loading capability of a generator stepup transformerisrelated directly to the output capacity of the generator to which itis connected, the transformer loading capability,including low temperaturecapability, shall be specified by the purchaser. The purchaser is advised toreferto ANSI/IEEE GuideC57.116 for transformers directly connected to generators. 3.5LowAmbient Temperature Load Capability Transformers,except for generatorstepup units (see Clause 3.4.1), shall be capable of an increase in loading for each degree Celsius thatthe daily average ambient temperature islower than25C, down to a minimum average ambient temperature of 0C. Selfcooled and watercooled unitsshallhavean increase of1.0% for each degree Celsius below 25Cand forcedaircooled and forcedair/forcedliquidcooled unitsshall have an increase of 0.75%for each degree Celsius below 25C. 4.Definitions 4.1 The following definitions apply in thisStandard: Displacement Angular displacement (of a polyphase transformer)the time angle,expressed in degrees, between the linetoneutral voltage of the referenceidentified highvoltage terminal (H1) and the line toneutral voltage of the corresponding identified lowvoltage terminal (X1). Note:The preferred connections for pa1 yphase iransformers are those which result in the smallest possible phaseangle displacements measured in aclockwise direction from the line-to neutral voltage of the reference identified high-voltage terminal (H1).Thus, standard threephase transformers have angular displacements of either zero or 30. Clock system (of phase displacement)a method of expressing the phasedisplacement between two windings by analogy to the hands of a clock. The phasors (taken torotatein acounter clockwise direction) representing the voltages between the neutral point (real or imaginary) and the corresponding terminals of two windings are viewed asthe handsof aclock.The angular difference between the phasors isexpressed asthe hour number, with the large (minute) CAN/CSAC88M90 - August 1990 Page 16Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.hand pointing at 12 representing the highvoltage winding, and the small (hour) hand representing the phasor of the lowor intermediatevoltage winding. Exciting current (of a transformer)the current flowing through a lineterminal of a winding when rated voltage is applied atrated frequency, the other winding(s) being opencircuited. Grounding Effectively groundedgrounded through a grounding connection of sufficiently low impedance (inherent or intentionally added,or both) that ground faultswhich may occurcannotbuild up voltages in excessoflimitsestablished for apparatus,circuits,or systems so grounded. Note:An alternating-current system, or portion thereof,may be said to be effectively grounded when, for all points on the system, or specified portion thereof,the ratio of zerosequence reactance to positivesequence reactance is not greater than3and the ratio of zerosequence resistance to positivesequence reactance is not greater than 1, for any condition of operation and for any amount of connected generator capacity. Groundedthe system,circuit, or apparatus referred tois connected to ground. Neutral groundedan intentional ground applied to the neutral conductor orneutral point of acircuit,transformer, machine, apparatus, or system. Reactance groundedgrounded through a reactor, a grounding transformer,or similar reactive device. Resistance groundedgrounded through a resistor. Solidly grounded (directly grounded)solidly grounded through a ground connection in which no impedance has been inserted intentionally. Impedance Impedance (of any tap)the impedance voltage expressed perunit, or as a percentage ofthe rated voltage of the tap, when current corresponding to the stated MVA base and the rated voltage ofthe tap iscirculated through the windings. Note:The impedance on any tap shallbe given on astated MVA base (not necessarily rated MVA). Impedance voltage (at rated current (principaltap)) (a) for two winding transformers, the voltage required to be applied at rated frequency to the lineterminals of a winding of a polyphase transformer,ortothe terminals ofa winding of a singlephase transformer, to cause theratedcurrent to flow through theseterminalswhen the terminals of the other winding are shortcircuited; (b) for multiwinding transformers, related to acertain. CAN/CSAC88M90 August 1990 Page 17 Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.combination oftwo windings, the voltage required to be applied at rated frequency to the line terminals for one of the windings of the combination for a polyphase transformer, orto the terminals of such a winding for a singlephase transformer,to cause a current to flow through theseterminals corresponding to the smaller ofthe rated power valuesof both windings of thatcombination, the terminalsofthe other windings of the combination being short circuited and the remaining winding(s)being opencircuited. Notes: (1)(Applicable to both Items (a) and (b).) The impedance voltage at rated current is usually expressed as a percentage of the rated voltage of the winding to which the voltage is applied. (2)(Applicable to Item (b)only.) In order to simplify certain calculations, it may be convenient torecalculate the impedance voltages of the various combinations intermsof the same reference power, whichshould always beindicated. Reactance voltagethe component of an impedance voltage in quadrature with the current. Resistance voltagethe component of an impedance voltage in phase with the current. Zerosequence impedancethe impedance expressed in ohms per phase atrated frequency between the terminals of a threephase transformerwhen allthree phases are excited from a singlephase source. Notes: (1)The zerosequence impedance is dependent not only on the connection of the winding to which it is applied, but also onthe connection of the other winding(s) and of its (their) neutral point(s). (2) The zerosequence impedance may, in certain circumstances, be dependent on the value of the current. Transition impedancea resistor orreactor consisting of one or more units bridging the tap in use and the tap nextto be used for the purpose of transferring loadfrom one tap position to theother without interrupting the current; at the sametimeitlimitsthe circulating current for the period thatboth tapsare bridged. Impulse Levels Lightningimpulse levelthe prescribed peak value ofthe lightningimpulse withstand voltage (full wave). Note:The lightning-impulse level(LIL) has been corrirnonly referred to asthe"BIL". Switching impulse levelthe prescribed peak value of the switching impulse withstand voltage (full wave). Insulation Uniform insulation (of a transformer winding)the insulation of a transformer winding when all its endsconnected to terminals have the same power frequency withstand voltage. CAN/CSAC88M90 August 1990 Page 18Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.Nonuniform insulation (of a transformer winding)the insulation of a transformer winding when it has an end intended for direct or indirectconnection to ground and is designed with a lower insulation level assigned tothis ground orneutral winding end. Linedrop compensator (in a voltage regulator)a device that causesthe voltageregulating relay to increase the outputvoltage by an amountthat compensates forthe impedance drop in the circuit between the regulator and a predetermined location onthe circuit (sometimes referred to asthe"load centre"). Liquid insulating mediamineral oil orflameretardant insulating liquids. Liquid Preservation Systems Conservator or expansion tankan auxiliary liquidtank, to provide for the expansion and contraction ofthe liquid in the main tankdue to temperature changes. Conservator or expansion tank systema method ofliquid preservation in which the main tankremains entirely filled with liquid overthe temperature rangespecified,by means of a conservatororexpansion tank. Sealed tank systema method of liquid preservation in which the interior of the tankis sealed from the atmosphere and in which the gas plus the liquid volume remains constant overthe temperature range. Load TapChanger Load tapchanger (LTC)a device for changing the tap of a winding suitable for operation whilethe transformer isenergized or onload. Selector switcha switching device capable of making, carrying, and breaking currents, combining the duties of a tap selector and a diverter switch. Changeover selectora device designed to carry current, but not to make or breakcurrent, used in conjunction with a tap selector or selectorswitchto enableits contacts and the connected tap to be used more thanonce when moving from one extreme position to the other. Cycle of operationthe movement of the tap changer from oneend ofits range tothe otherand the returnmovement to its original position. Diverter switch-a switching device used in conjunction with a tap selector to carry,make,and break current on taps thathave already beenselected by the tap selector. CAN/CSAC88M90 August 1990 Page 19 Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.Driving mechanismthe means by which the tap changer is actuated. Note:The mechanism may include independent means of storing energy (eg, a load spring mechanism) to control the speed and to ensure the completion of an operation. Tap selectora devicedesigned to carry current, butnotto make or break current,used in conjunction with a diverter or arcing switch, to select tap connections. Losses Load loss (of a transformer)those losses which areincident to the carrying ofload. Note:Load lossincludes 12R lossin the windings dueto load current;stray loss due to stray fluxesin the windings, core clamps,etc; and also the loss due to circulating currents, if any, in parallel windings or conductors. Excitation loss(of a transformer)the active power absorbed when rated voltage at rated frequency is applied to the terminals of one of the windings, the other winding beingopencircuited. Note:Excitation lossincludes coreloss, dielectric loss, and 12R lossin the windings due to exciting current. Total loss(of a transformer)the loss represented by the sum of the excitation and the load losses; the totallossdoes notinclude thelosses of auxiliaries such asfan and pump motors. Phase Connections Delta connectionthe windings so arranged thatthe phase windings of a threephase transformer, or the windings for the same rated voltage of singlephase transformers associated in athree phase bank, are connected inseriesto form a closed circuit. Starconnectionthe windings so arranged thatone end of eachof the phasewindings of a polyphase transformer, or ofeachof the windings forthe same rated voltage of singlephase transformers associated in a polyphase bank, isconnected to acommon point (the neutral point) and the otherend to its appropriate line terminal. Zigzag connectionthe windings so arranged that one end of each phase winding of a polyphase transformer isconnected to acommon point (neutral point), and each phase winding consists of two parts in which phasedisplaced voltages are induced.These two parts normally have the same number of turns. Polarity Relative lead polarity (of atransformer)a designation of the relative instantaneous directions of current inits leads. Notes: (1)Primary and secondary leadsare said to have the same polarity when, at a given instant during most of each half-cycle, the current entersan identified, or marked, primary lead and leaves CAN/CSAC88M90 August 1990 - Page 20 Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.the similarly identified, or marked,secondary lead inthe same direction as if the two leadsformedacontinuous circuit. (2) The relative lead polarity of a singlephase transformer may be either additiveorsubtractive.If one pair of adjacent leads from the two winding's isconnectedtogether and voltage applied to one of the windings, then the relative lead polarity is (a) additive if the voltage acrossthe other two leads of the windings is greater thanthat of the higher voltage winding alone; and (b) subtractive if the voltage acrossthe other two leadsof the windings islessthanthat of the highervoltagewinding alone. (3) The relativelead polarity is indicated by identification markson primary and secondary leadsof like polarity, or by other appropriate identification. (4) The polarity of a polyphase transformer is fixed by the internalconnections between phases as wellas by the relative location of leads; it is usually designated by means of a phasor diagram showing the angular displacement of windings and a sketch showing the marking of leads.The phasor lines of the diagram represent induced voltages and the recognized counterclockwise direction of rotation is used.The phasor representing any phase voltage of agiven winding is drawn parallel to thatrepresenting the corresponding phase voltage of any other winding under consideration. Ratings Rating (of a power transformer)--the rated load in MVA together with any other assigned characteristics, such as voltage, current, and frequency assigned by the manufacturer.Itshallbe regarded as atest rating thatdefines an output that can be taken from the apparatus underprescribed conditions oftest, and within the limitationsof thisStandard. Continuous ratingthe maximum output in MVA thatcan be carried continuously without exceeding established temperaturerise limitations,under prescribed conditions of test, and within the limitationsof established standards. Shorttime ratingthe maximum output in MVA thatcan be carried for a specified short time without exceeding established temperaturerise limitations, underprescribed conditions of test, and within the limitations of established standards,and when the transformeris at approximately ambient temperature at the timethe loadis applied. Base MVA rating (of a transformer)the sum of the equivalent ONAN ratings of all windings using the principal tap, divided by two.The base MV'A rating may be an equivalent rating and is not intended to be athermal rating. For types of cooling other than ONAN,the equivalent ONAN rating shallbe obtained by multiplying (a) ONWF rating x0.75; (b) ONAF (ONAN plus 1/3)rating x0.75; (c)ONAF/ONAF CONANrating plus 2/3)rating x0.6;or (d)OFWF,OFAF,or ODAF rating x0.6. CAN/CSAC88M90 August 1990 Page 21 Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.Rated MVA (of a transformer)the output thatcan be delivered continuously, or for thetime specified, at rated secondary voltage and rated frequency without exceeding the specified temperature riselimitations under prescribed conditions of test, and within the limitations of established standards. Shorttime rating(of a grounding transformer)--the product of the ratedlineto--neutral voltage at rated frequency and the maximum constant current thatcan flowin the neutral forthe specified time without causing specified temperaturerise limitations to be exceeded, and within the limitations of established standards for such equipment. Rating of a singlephase seriesvoltage regulator-the product of the ratedloadin amperes and the rated range of regulation in volts. Rating of a threephase seriesvoltage regulatorthe product of the ratedloadin amperes and the rated range of regulation in volts multiplied by 1.732. Ratio Turns ratio (of a transforiner)the ratioof the numberofturns in the highvoltage winding to thatin the lowvoltage winding. Note:Inthe case of a transformer having taps for changing its voltage ratio, theturnsratio is basedon the number ofturns corresponding tothe principal tap of the respective windings to which operating and performance characteristics are referred. Reactor Reactoradevice used forintroducingimpedance into an electric circuit,the principal element of which is inductive reactance. Shuntreactor-areactor intended forconnection in shuntto an electric system for the purpose of drawing inductive current. Regulation Voltageregulation (of a transformer)the change in output (secondary)voltage thatoccurs when the load is reduced from rated valuetozero, with the applied (primary)voltage maintained constant. Note:In the case of multiwinding transformers, the loads on all windings, at specified power factors, are to be reduced from rated power to zero simultaneously. The regulation at a given power factor may be expressed per unitor as a percentage on the base of the rated secondary voltage. Rated range of regulation (of a seriesvoltage regulator)the amount thatthe regulator willraise orlowerits rated voltage with rated voltage applied. Note:The rated range may he expressed per unit, or as a percentage, of rated voltage; or it may beexpressed inkilovolts. CAN/CSAC88M90 August 1990 - Page 22 Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.Seriesvoltage regulatora transformer having one or more windings excited from the system circuit or a separate source,and one or more windings connected in series with the system circuit for adjusting the voltage in steps, without interrupting the load. Tap changer for deenergized operationa device for changing the voltage ratioof the windings; it issuitable for operation only when the transformer is not energized. Taps Tap (in a transformer)---a connection brought out of a winding at some point between its extremities, to permit changing the turns ratio. Full MV'A tap (in a transformer)a tap through which the transformer can deliver an output equal to rated MVA without exceeding the specified temperature rise. Principal tapthe tap corresponding tothe rated voltage ofthe winding at noload and to which the performance characteristics are referred. Plus tapatap so located asto introduce intothe active part of the winding concerned a greater number of turnsthan those corresponding to the principal tap. Minus tapatap so located asto introduce into the active part of the winding concerned fewerturnsthan those corresponding to the principal tap. Reduced MV'A tap (in a transformer)a tap through which the transformer can only deliver an output less thanrated MVA without exceeding the specified temperature rise. Tap rangethe variation range of the taps expressed as a percentage of the principal tap, the principal tap being considered as Note:If thisvariation ranges from 100 -I-ato 100 b,the tap range is said to be +a per cent, b per cent, ora per cent if ab. Tap stepthe difference in voltage between two adjacent taps expressed as a percentage of the principal tap voltage. Temperature Ambient temperaturethe temperature of the external cooling medium into which the heatis finally dissipated. In the case of watercooled transformers, thisisthe temperature ofthe water as it entersthe waterheat exchanger. Resistance method (of temperature determination)the determination of the average temperature of a winding by comparison of the resistance of the winding at the temperature to be determined with the resistance at a known temperature. CAN/CSAC88M90 August 1990 Page 23 Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.Thermometer method (of temperature determination)the determination of the temperature by alcohol thermometers, by resistancethermometers, or by thermocouples; any of these instruments beingapplied to the hottest accessible part ofthe apparatus. Temperature risethe difference between the temperature of the part under consideration and the temperature of theair, or of the water at the intakeofthe cooling equipment for aircooled or watercooled transformers, respectively. Terminals and Neutral Point Terminala conducting element intended for connecting awinding to external conductors. Line terminalaterminal for connection to a phase conductor of a system. Neutral terminal (a) for polyphase transformers and polyphase banksof singlephase transformers,terminal(s) connected to the neutral point of astar connected orzigzagconnected winding; and (b) for singlephase transformers, theterminal intended for connection to a neutral point of asystem. Neutral pointthe point of asymmetrical system of voltages that is normally at zero potential. Note:For astar-connected or zigzagconnected polyphase system, it is the common point. Tests Acceptance testa testto demonstrate compliance of a device with the purchaser's requirements. Dielectric teststests that consist of the application of a voltage higher thantherated voltage for a specified timefor the purpose of determining the adequacy against breakdown of insulation materials and spacing undernormalconditions. Type testa test made on atransformer thatis representative of othertransformers to demonstrate thatthesetransformers comply with specified requirements not covered by routinetests. Note:A transformer is considered to be representative of others if it is fully identical in rating and construction, but thetype test may also be considered valid if it is made on a transformer that has minor deviations of rating or other characteristics.The acceptability of the type test in thesecircumstances should be the subject of agreement between the manufacturer and the purchaser. Routine testatest to which each individual transformer is subjected. CAN/CSAC88M90 - August 1990 Page 24 Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.Thermally upgraded papercellulose paperbased insulation which has been upgraded from Class 105(Class A) insulation to inhibit the thermal degradation process. Suchinsulation has alife characteristic at 120C,marked in terms of tensile strength and dielectric strength,equal to or better than Class 105cellulose paper, and should give alifeexpectancy as defined in ANSI/IEEE Standard C57.92(Figure1) for 65Crisetransformers.(See also ANSI/IEEE Standard C57.12.80.) Transformers Transformeran electric device without continuously moving parts that by electromagnetic induction transfers electric energy from one or more circuits to one or more othercircuitsatthe same frequency,usually with changed valuesof voltage and current. Autotransformera transformer in which part of one winding is commonto both the primary and the secondary circuits associated withthat winding. Booster transformera transformerof which one winding is intended to be connected in series with acircuit in orderto alter its voltage. The other winding is an energizing winding. Grounding transformera transformer intended primarily forthe purpose of providing aneutral point for grounding purposes. Indoortransformer-a transformer that,because of its construction, must be protected from the weather. Multiwinding transformera transformer having more than two windings. Loadtapchanging (LTC) transformera twowinding or multiwinding transformer having one or more windings provided with taps and loadtapchanging switchgear for adjusting the voltage in steps without interrupting the load. Outdoor transformera transformer of weatherproof construction. Phaseshifting transformera transformer that advances or retardsthe phaseangle relationship of one circuit with respect to another. Voltage Nominal voltage (of a system or circuit)a nominal value assigned to a system orcircuit of agiven voltage class for the purpose of convenient designation. Note:The term"nominal voltage" designates the line-to-line voltage, as distinguished from the line-to-neutral voltage. It applies to all parts of the system of circuit. Rated voltage(ofequipment or of a winding)-the voltage to which operating and performance characteristics are referred. CAN/CSAC88M90 August 1990 Page 25 Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.Rated primary voltage (of a transformer)---the voltage obtained fromthe rated secondary voltage by applying the turnsratio. Rated secondary voltage (of a transformer)the voltage at which the transformeris designed to deliverrated power andto which operating and performance characteristics are referred. Voltage classificationthe level of power frequency voltage selected by the purchaser as a basison which to identify the system of insulation levels and associated tests applicable to the transformer. Voltageregulating relaya voltagesensitive device thatis used on an automatically operated seriesvoltage regulator or LTC transformertocontrol the voltage of theregulated circuit. Windings Common winding (of an autotransforiuer)thatpart of the autotransformer winding which is common to both the primary and the secondary circuits. Series winding (of an autotransforiuer)thatportion ofthe autotransformer winding which is not common to both the primary and the secondary circuits but is connected in seriesbetween the input and output circuits. Primary windingthe winding on the energy input side. Secondary windingthe winding on the energy output side. Stabilizing windinga deltaconnected winding used on star connected transformers or autotransformers, for any or all ofthe following purposes: (a) to facilitate the flowof zero phasesequence currents; (b) toreduce thethirdharmonic voltages inthe transformer windings andin the system; (c) toreduceinterference with communication circuits due to thirdharmonic currents in the lines and ground; (d) to stabilize the neutral point ofthefundamental frequency voltages. Note:The stabilizing winding may be used to supply a separate load when adequately rated. 5.Terminal Markings, Polarity, and Angular Displacement 5.1General Clause 5 specifies the polarity, preferred methods of connection, and associated angle of phaseshift, and the method of marking terminals brought out of the transformer tank.The marking of terminalsinsidethe tankisnot specifically covered, except that theseterminals shall be marked with numbers or letters thatwill permit convenient reference and cannotbeconfused with the marking CAN/CSA-C88M90August 1990 Page 26 Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.ofthe terminals brought out of the tank. Note:It is recognized that from time to time therewillarise special conditions not covered by Clause 5and very difficult to cover by any set of general rules. 5.2Identification of Windings 5.2.1 In general, the windings of atransformer shallbe distinguished from one another as follows: (a)Twowinding transformers shallhave their windings designated as High Voltage (HV or H) and Low Voltage (LV or X). (b) Transformers with more than two windings shallhave their windings designated as H,X,Y,and Z. (C) Whentransformer windings are physically arranged with one above the otheronthe core,as, for example, in the caseof two LV windings designated X and Y,the ratingplate shall indicate which winding ison top. 5.2.2 The sequence of designations shall be determined asfollows: (a) The highest voltage winding shallbe designated as HV or H. (b) The other windings shallbe designated in order of decreasing voltage as X,Y,and Z. (c) Iftwo(ormore)windings have thesame voltage and different powerratings, the higher powerwinding shallreceive the prior letter designation ofthetwo (or more) letters available, according to the sequence by voltage as explained above. (d) Iftwo or more windings have the same power and voltage ratings, the designations of these windings shallbe arbitrarily assigned. 5.3 Marking of Terminals 5.3.1 In general, external terminals shallbe distinguished from one another by marking each terminal with a capital letterfollowed by a subscript number,eg, for a threephase twowinding transformer the terminalsofthe H winding would be marked H1, H2, H3; the terminalsofthe X winding would be marked X1,X2, X3, etc. 5.3.2 The markings shallbe so applied thatif,for example, the phase sequence of voltage on the highest voltage winding isinthe time order H1, H2, H3, itwill be in thetimeorder of X1, X2,X3 and Y2, Y3, etc,on the otherwindings. 5.3.3 A neutral terminalof athreephase transformer shall be marked with the proper letter followed by a subscript 0;eg, H0,X0, etc. A neutral terminalcommon to two or more windings of a single or threephase transformer shallbe marked with thecombination ofthe proper winding letters,each followed by the subscript 0;eg, H0X0, asin the caseof autotransformers. Note:A terminalbrought out from the winding for some other use thanthatof a neutral terminal (eg, a 50% starting tap) shall be CAN/CSAC88M90 August 1990 Page 27Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.marked as a tap terminal. 5.3.4 If a transformer has a twoterminal winding with oneterminal grounded and the other ungrounded, the subscript 2terminal shall be the grounded terminal. 5.4Orderof Numbering Terminals 5.4.1 SinglePhase Transformers 5.4.1.1 Except as specified in Clause 5.4.1.2,theterminals of any winding brought out of thetankshall be numbered 1,2,3,4,5,etc,the lowest and highest numbers marking thefull winding and the intermediatenumbers marking fractions of windings or taps. All numbers shallbe so applied thatthe potential difference from any terminal having a lower number toward any terminal having a higher numbershallhavethe same sign at any instant. 5.4.1.2 Inthe case of singlephase autotransformers, the highvoltage and lowvoltage terminals shall be considered as belonging to two entirely separate windings and numbered accordingly. The common neutral terminal shall,however, be marked with the combination of the appropriate winding letters and numbers, eg, H2X2. 5.4.1.3 Ifa winding isdivided intotwo or more parts for seriesmultiple connections and theterminals of these parts are brought out ofthe tank, Clause 5.4.1.1 shall apply for the seriesconnection, with the addition thattheterminals of each portion of the winding shall be given consecutive numbers. 5.4.2ThreePhaseTransformers 5.4.2.1 Marking of Full Winding Terminals The threeterminals for each winding that connect to thefull phase windings shall be marked H1, H2,H3, X1,X2, X3,Y3, etc, respectively. 5.4.2.2 Tap Terminals Where tap terminals are brought out ofthetank (neutral terminal excepted)they shallbe marked withthe proper letterfollowed by the numbers 4,7,etc,for one phase,5,8,etc, for another phase, and 6,9,etc,forthe third phase. For delta connection, the order of numbering tap terminals shall be as follows:4,7,etc, from terminal 1toward terminal 2;5,8, etc,from terminal 2toward terminal 3;.and 6,9,etc, from terminal 3toward terminal 1. For starconnection, the orderof numbering tap terminals shall be as follows:4,7,etc, from terminal 1toward neutral;5,8, etc,from terminal 2toward neutral; and 6,9,etc,from terminal 3 towardneutral. CAN/CSAC88M90 August 1990 - Page 28Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.5.4.2.3 Interphase Connections Made Outside the Transformer Tank Where the interphase connections are made outside the tank,the terminals shallbe marked with the proper letterfollowed by the numbers 1,4,7,10,etc,for one phase;2,5,8,11,etc,for the second phase; and 3,6,9,12, etc,for the third phase. The markings shallbe so applied that,when a starconnection is made by joiningtogether the highest numbered terminals of each phase, all rules here given apply,except those outlined in Clause 5.3.3 5.5Location of External Terminals and Polarity of SinglePhase Transformers 5.5.1Location of External Terminals 5.5.1.1 The H1 terminalshall be brought out as the righthand terminal of the highvoltage group asseen when facing the highest voltage side of the tank, and other H terminals shall be brought out in numerical orderfrom right to left. 5.5.1.2 When the highvoltage winding has only one terminal brought out through a ratedvoltage bushing (the other terminal to be grounded), the grounded terminal shallbe designated as H2. For polarity marking and testing, the H1 terminal shallbe considered as located on the right,regardless of its actual location. 5.5.1.3 When the highvoltage terminals are brought out through two bushings of different insulation levels, the bushing having the higher voltage level shallbe designated as H1 and shall be located on the righthand side facing the highvoltage side ofthetank. 5.5.1.4 Singlephase autotransformer terminals shall,asfar as practicable, be marked in accordance with the requirements for subtractive polarity specified in Clause 5.5.2.1. 5.5.2 Polarity 5.5.2.1 Subtractive polarity shallbe standard for all singlephase power transformers.Forsubtractive polarity the lowvoltage terminal adjacent to H1 shall be marked X1. 5.5.2.2 The same will apply between the H and Y winding, and between the H and Z winding, where such windings exist. 5.6Location of External Terminals and Angular Displacement of ThreePhase Transformers 5.6.1Location of External Terminals CAN/CSAC88M90 August 1990 Page 29 Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.5.6.1.1 The H1 terminal shall be brought out as the righthand terminal of the highvoltage group as seen when facing the highest voltage side of the tank.The H2 and H3 terminals shall be brought outso that the threeterminalsare arranged innumerical order reading from right to left when facing the highest voltage side of the tank. The preferred location ofthe H0 terminal,if present, shallbe to the right of the H1 terminal as seenwhen facing the highest voltage sideof the tank. 5.6.1.2 The X1 terminal shallbe brought out as the lefthand terminal of the X group as seen when facing the X winding sideof thetank. The X2 and X3 terminalsshallbe brought out sothatthe three terminals are arranged in numerical order reading from leftto right when facing the X winding side of the tank. The preferred location ofthe X0 terminal, if present, shall be to the leftofthe Xj terminal as seenwhen facing the X winding sideofthe tank. 5.6.1.3 The Y winding and Z winding terminals, if present, shall be brought out and numbered in the samemanner asthe X winding terminals. 5.6.1.4 Autotransformer terminals shall, as faras practicable, be marked in accordance withthe requirements for corresponding multiwinding transformers. 5.6.2Angular Displacement 5.6.2.1 The convention for the direction of rotation ofthe voltage phasors shall be taken as counterclockwise. 5.6.2.2 In orderthatthe markings of terminal connections between phases of a threephase transformer indicate definite phase relations, they shallbe madein accordance withone ofthe threephase groups shownin Figure 1. 5.6.2.3 The preferred angular displacement between windings of threephase power transformers with deltadelta, starstar, deltazigzag, or zigzagdelta connections shall be00(see Figure 1). 5.6.2.4 The preferred angular displacement between windings of threephase power transformers with stardelta, deltastar, starzigzag, or zigzagstar connections shall be 300 with thelow voltage neutral phasorlagging (see Figure 1). 5.6.2.5 For multiwinding transformers, the phasor forthe highest voltage winding shallremain thereference phasor, and the symbol for this winding shallbe given first.Other symbols shallfollow in the CAN/CSAC88M90 August 1990 Page 30Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.orderof the rated voltages of the windings. P GROUP 2 ANGULAR DISPLACEMENT GROUP1 T__ANGULAR DISPLACEMENT 300 00 X2 H2X2 H1A DELTA-STAR (Dd 0)(Dy 1) Xl H3Xi la X3 Hi lb H3 2b X2 H2X2 STAR-STAR (YyO) HiH3X3 lc H2 STAR-DELTA (Ydl) xi Hi H3 2c X3 2dld xl X3 Note:Letters in brackets are IEC designations for winding connections.Figures in brackets are IEC designations for angular displacement basedon the clock-hour system. See definition for clock system (of phase displacement) in Clause 4of this Standard and IEC Publication No. 76, Part 4. Figure 1 Angular Displacement of ThreePhase Transformer 5.7Terniinal Markings for SeriesVoltage Regulators 5.7.1 Terminals that are connected to the load shall be designated by an L,and those connected tothesourceshallbe designated by an S. Example: Inthecaseof asingle-phaseregulator, theterminalswouldbe marked5,L, andSL. Inthecaseof athree-phaseregulator, theterminalswouldbe marked Si,S3,L1,L2,L3,and, if a neutralterminalis provided,50L0. 5.7.2 For threephase regulators, when facing the sourceside of the regulator, the S terminal shall be brought out on the right, and CAN/CSAC88M90 August 1990 Page 31 Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.the S2 and S3 terminals shallbelocated in numerical order, reading from right to left.The L1 terminal shall be brought out as the lefthand terminal of the L group as seen when facing the load sideof the tank,andthe L2 and L3 terminals shall belocated in numerical order,reading from leftto right. 5.7.3 The 50L0 terminal, if present, shall be located to the leftof the S3 terminal as seenwhen facing the sourceside ofthe tank. 6. Types Based on Cooling Methods 6.1General Liquidfilled transformers shallbe classified as outlined in Clauses 6.2 to 6.6,based on the cooling methods used. Note: Energy losswithin the windings,core, and other parts of the apparatus is released as heat to the cooling medium within the tank.Circulation of the cooling medium allows thisheat to be dissipated by means of radiators or heat exchangers. 6.2 Cooling Medium 6.2.1Internal Cooling Medium The internal cooling medium shall be designated as follows: SymbolCooling medium 0A mineral insulating oil conforming to CSA Standard C50 and EEMACStandard B6l LA flameretardant insulating liquid 6.2.2External Cooling Medium The external cooling medium shall be designated as follows: SymbolCooling medium AAir WWater 6.3 Type of Circulation The type of circulation for both internaland external cooling mediums shallbe designated as follows: SymbolType of circulation NNatural FForced DForceddirected (internalcooling medium only) CAN/CSAC88M90 August 1990 Page 32Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.Note:In forced-directed flow, the oilis directed from the coolers intothe inletductsof all or some windings of the transformer, so as to pump the oil through the windings. 6.4 Designations and Orderof Symbols The designations and orderof symbols shallbe as shownin Table 1. Table 1 Designations and Order of Symbols 1st Letter2nd Letter3rd Letter4th Letter Internal coolingType ofinternalExternal coolingType ofexternal mediumcirculationmediumcirc ulation 6.5Standard Type Designations The standard types of transformers with their designations shall be as follows: Standard Type Designation (a) Oilfilled natural cooling ONAN; (b) Oilfilled water cooling ONWF; (c) Oilfilled forcedair cooling ONAF; (d) Oilfilled forcedoil water cooling OFWF; (e) Oilfilled forcedoil forcedair cooling OFAF; (f) Oilfilled forceddirected oil forcedair coolingODAF; (g) Oilfilled forcedoil natural coolingOFAN; (h) Flameretardant liquidfilled natural coolingLNAN; (i) Flameretardant liquidfilled water cooling LNWF; (j) Flameretardant liquidfilled forcedair cooling LNAF; (k) Flameretardant liquidfilled forcedliquid water cooling LFcF; (1) Flameretardant liquidfilled forcedliquid forcedair cooling LFAF; (m) Flameretardant liquidfilled forcedliquid natural cooling LFAN. 6.6 Type Designation for More Than One Method of Cooling Where the apparatus has more thanone method of cooling, the type designations for all methods shall be stated, separated from each other by an oblique (/). In all casesof multiple cooling, the power for each stage of cooling shallbe designated. Note: Typical exa.inples are (a)ONAN/ONAF 30/40 MVA--an oil-filled transformer having a naturally cooled (ONAN) rating of 30 MVA and aforced-air-cooled (ONAF)rating of 40MVA; (b)ONAN/ONAF/ONAF 30/40/50 MVA--a transformer having a naturally cooled CONAN) rating of 30 MVA, a forced-air-cooled (ONAF) rating of 40MVA achieved by operating only part of the fans, and an increased forced-air-cooled (ONAF) rating of 50MVA when allthe fansare operating; (c)ONAN/ONAF/OFAF 30/40/50 MV'A--a transformer having a naturally cooled (ONAN) rating of 30 MVA, aforced-air-cooled (ONAF) rating CAN/CSAC88M90 August 1990 Page 33Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.ot 40 MVA with only the tans operating, and a torced-oil torced- air-cooled (OFAF) rating ot 50MV'A with both tansand oil pumps operating; and (ci)ONAN/ONAF/ODAF 30/40/50 MV'A--a transtormer having a naturally cooled (ONAN) rating ot 30 MVA, a torced-air-cooled (ONAF) rating of 40 MVA with only the fans operating, and a forced-directed oil- torced-air-cooled (ODAF) rating ot 50 MVA with both tans and pumps operating. For ODAF theinstruction bookfor the transformer shall identify windings with and without forceddirected flow cooling. 7. Ratings 7.1Preferred MVA Ratings The preferred MVA ratings are statedin Table 2for singlephase and threephase twowinding transformers, multiwinding and auto transformers when only two sets of terminals are brought out of the tank, and shuntreactors (for basis of Mvar rating see Clause 20.1). Table 2 Preferred MVA Ratings for Transformers Preferred ratings in MVA 0.5550500 0.676.6766.7667 0.838.3383.3833 110100 1.2512.5125 Singlephase 1.6716.7167 220200 2.525250 3.3333.3333 440400 1.5151501500 2202002000 2.525250 330300 3.7537.5375 Threephase 550500 660600 7.575750 101001000 121201200 Note:For multiple-rated transformers, the preferred MVA rating tor theONAN rating is according toTable 2; tor the tirst stage ot torced cooling(ONAF)thepreterredincrease is 33%, and torthe second stage ottorced cooling (ONAF/ONAFor OFAF)the preterred CAN/CSAC88M90 August 1990 Page 34 Licensed for/Autoris Lawrence Duong, Sold by/vendu par CSA on/le 3/25/2010. Single user license only. Storage, distribution or use on network prohibited./Permis d'utilisateur simple seulement. Le stockage, la distribution ou l'utilisation sur le rseau est interdit.increase is 66? of the ONAN rating. 7.2Basis of MVA Rating 7.2.1 The rating ascribed shallbe that output the transformer can deliver atits ratedsecondary voltage underservice conditions outlined in Clause 3, without exceeding the temperaturerise limitations specified in Clause 9. Notes: (1) The rated MV'A isthe product of the secondary kA, the secondary kV, and the appropriate phase factor (/3 for three- phase). (2) Unlessotherwise specified, it is assumed thatthe energy flowsfrom the high-voltage tothe lowvoltage winding. 7.2.2 The MV'A rating shall be based on ratedsecondary voltage maintained by impressing on the primary winding the voltage necessary to compensate forthe effectof regulation of the transformerat ratedsecondary current and at a power factor of90% lagging. 7.2.3 An autotransformer with a stabilizing winding for connection to an external load,or amultiwinding transformer with more than two setsof leads brought out ofthe tank, has no standard basis of power rating. All simultaneous loading conditions shall be clearly specified by the purchaser. Foreach loading condition, the MV'A rating and power factor shall be specified for all windings. 7.2.4 Transformers or autotransformers withan LTC in the secondary winding shall have reduced MV'A capacity on all tapchanger positions that givevoltages below the principal rated tap voltage. The current rating forsuch lowervoltage positions shall be that of the principal rated tap voltage position. 7.3Basis of Voltage Rating 7.3.1 The voltage ratings shallbe based on theturnsratio,ie, noload values. Note:The ratioof voltages willbe subject to the effect of regulation atthe various loadsand power factors. 7.3.2 Transformers shallbe capable of delivering rated output MV'A, at a power factorof 90%lagging with 5%above ratedsecondary voltage, without exceeding thetemperature ises as defined in Clause 9. 7.3.3 Transformers shallbe capable of operating at noload with the primary voltage required forthe conditions of Clause 7.3.2, or10% above ratedvoltage, whichever is the higher, without exceeding the temperature rises as defined in Clause9. CAN/CSAC88M90 - August 1990