ANSI IEEE C57.105-1977 Guide for Application of Transformer Connections in Three-Phase Distribution Systems.pdf

1、IEEE C57.105-1978 (R2008)IEEE Guide for Application of Transformer Connections in Three-Phase Distribution SystemsSponsorTransformers Committeeof theIEEE Power Engineering SocietyApproved 2 June 1977Reaffirmed 11 June 1987Reaffirmed 18 June 1992Reaffirmed 27 March 2008Institute of Electrical and Ele

2、ctronics EngineersSecretariatEdison Electric InstituteInstitute of Electrical and Electronics EngineersNational Electric Manufacturers AssociationApproved May 19, 1978Approved March 2, 1989American National Standards InstitutePublished byThe Institute of Electrical and Electronics Engineers, Inc 345

3、 East 47th Street, New York, NY 10017No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without theprior written permission of the publisher.American National StandardAn American National Standard implies a consensus of those substantially conc

4、erned with its scope and provisions.An American National Standard is intended as a guide to aid the manufacturer, the consumer, and the general public.The existence of an American National Standard does not in any respect preclude anyone, whether he has approved thestandard or not, from manufacturin

5、g, marketing, purchasing, or using products, processes, or procedures notconforming to the standard. American National Standards are subject to periodic review and users are cautioned toobtain the latest editions.CAUTION NOTICE: This American National Standard may be revised or withdrawn at any time

6、. The procedures ofthe American National Standards Institute require that action be taken to reaffirm, revise, or withdraw this standard nolater than five years from the date of publication. Purchasers of American National Standards may receive currentinformation on all standards by calling or writi

7、ng the American National Standards Institute. Copyright byThe Institute of Electrical and Electronics Engineers, IncNo part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without theprior written permission of the publisher.iiiForeword(This Forewor

8、d is not a part of ANSI/IEEE C57.105-1978, American National Standard Guide for Application of TransformerConnections in Three-Phase Distribution Systems.)In the fall of 1968, a Working Group was formed by the Performance Characteristics Subcommittee of the IEEETransformers Committee to prepare a us

9、ers guide for application of Y-Y transformers considering user systems,manufacturing capabilities, tank heating, ferroresonance and telephone interference. The scope of the proposed usersguide was subsequently expanded to cover the full range of transformer connections commonly used in 3-phasedistri

10、bution systems with emphasis on those characteristics of connections which distinguish one from another, appearmost prominently with asymmetrical system conditions, and affect the selection of connections.The guide assumes the reader has an educational or practical background equivalent to that of a

11、 graduate electricalengineer with some knowledge of transformers and distribution practices. Recognizing from the start, however, thatthe guide would be most needed by and most useful to the engineer with relatively little experience, the WorkingGroup has incorporated explanatory material where cons

12、idered to be helpful.The Institute wishes to acknowledge its indebtedness to those who have given so freely of their time and knowledge tothe development of this guide.At the time it approved this standard, C57 had the following membership:H. D. Lewis, Chair C. R. Wilmore, Secretary Bonneville Power

13、 Administration George W. IliffElectric Light and Power Group R. R. BestI. O. BerkhanI. H. KoponenJ. P. Markey (Alt)P. H. PhilippidisW. A. RichterB. F. SmithE. A. VillasusoInstitute of Electrical and Electronics Engineers .S. BennonW. P. BurtJ. C. DuttonD. C. Johnson (Alt)L. W. LongD. E. MasseyNaval

14、 Facilities Engineering Command Leonard W. JohnsonNational Electrical Manufacturers Association L. C. AicherW. R. CourtadeJ. D. DouglassW. C. KendallG. W. Mayall (Alt)W. J. McNuttNorman M. Neagle (Alt)R. L. SchwabR. E. Uptegraff, JrG. C. Wilburn (Alt)Rural Electrification Administration J. C. Arnold

15、, JrTennessee Valley Authority L. R. SmithUnderwriters Laboratories W. A. Farquhar (Alt)ivE. J. HuberU. S. Bureau of Reclamation R. H. RichardsonThis guide was developed by a Working Group of the Performance Characteristics Committee of the IEEETransformers Committee of the IEEE Power Engineering So

16、ciety which had the following membership:L. W. Long, Chair J. D. BorstD. E. MasseyK. M. McWilliamsD. A. RoachD. R. SmithOther members who have served in the past are:E. R. Freitag*R. H. HollisterA. M. LockieR. L. MacdonaldR. L. Schmid*First chairmanSpecial acknowledgement is due C. R. French, Chairm

17、an of the Performance Characteristics Subcommittee at the timeof Working Group formation, who saw the need for this work and contributed substantially to the initial efforts.The Transformers Committee of the IEEE Power Engineering Society of 1976 and 1977 reviewed and approved thisstandard.When this

18、 standard was approved June 2, 1977, the IEEE Standards Board had the following membership:William R. Kruesi, Chair Irvin N. Howell, Jr, Vice Chair Ivan G. Easton, Secretary William E. AndrusJean Jacques ArchambaultMark BarberEdward J. CohenWarren H. CookLouis CostrellR. L. CurtisDavid B. DobsonR. O

19、. DuncanCharles W. FlintJay ForsterRalph I. HauserJoseph L. KoepfingerIrving KolodnyBenjamin J. LeonThomas J. MartinDonald T. MichaelVoss A. MooreWilliam S. MorganWilliam J. NeiswenderRalph M. ShowersRobert A. SodermanLeonard W. Thomas, SrB. W. WhittingtonvCLAUSE PAGE1. Scope.12. Electrical Connecti

20、ons 12.1 Primary and Secondary Systems 12.2 and Y Connections 22.3 Zigzag-Connected Winding . 32.4 TT Connections 52.5 Terminal Markings, Phase Relations, and Paralleling . 52.6 Connection of the Neutral 93. Magnetic Circuits 93.1 General Transformer Design 93.2 3-Phase Transformer Core Configuratio

21、n 103.3 Magnetic Circuit Effects on 3-Phase Transformer Behavior. 124. Harmonic Currents and Voltages 134.1 Exciting Current Harmonics 134.2 Harmonic Generation . 134.3 Flow on 3-Phase System 144.4 Telephone Noise 155. Primary Faults .155.1 Types and Clearing of Faults . 155.2 Ground Faults. 155.3 O

22、pen Conductor Faults 166. Unbalanced Loads and Secondary Ground Faults 176.1 Phase-to-Neutral Loads 176.2 Phase-to-Phase Loads 186.3 Secondary Faults 197. Ferroresonance 207.1 Qualitative Description 207.2 Transformer Connections Highly Susceptible to Ferroresonance . 227.3 Measures to Minimize the

23、Probability of Ferroresonance with Ungrounded Primary Connection. 247.4 Transformer Connections Least Susceptible to Ferroresonance 257.5 Measures to Minimize the Probability of Ferroresonance with Grounded Primary Connections . 267.6 Bibliography. 278. Unsymmetrical Banks and Special Connections 27

24、8.1 T-Connected. 278.2 Circulating Delta Currents . 278.3 Grounded Delta Secondary 288.4 Open- Secondary . 308.5 Open-Y primary to 4-Wire 208 V Service. 318.6 Effect on Voltage Balance . 31viCLAUSE PAGE9. References and Bibliography 319.1 General . 319.2 Ferroresonance . 319.3 Special Connections .

25、33Copyright 1978 IEEE All Rights Reserved 1IEEE Guide for Application of Transformer Connections in Three-Phase Distribution Systems1. ScopeThis guide concerns transformer connections in 3-phase distribution systems. Distribution systems are characterizedby primary voltages up to and including 34.5

26、kV, usually have a preponderance of connected transformers with low-voltage windings below 1000 V and furnish electric service to consumers. The characteristics of the varioustransformer connections and possible operating problems under normal or abnormal conditions are treated.All combinations of a

27、nd Y, grounded and ungrounded, T connected, zigzag, and certain special connections areconsidered. Only two-winding transformers are included.Phasing procedures and loading practices are not covered. Guides for loading of oil-immersed and dry-typetransformers are available in publications of the Ame

28、rican National Standards Institute: American National StandardC57.91-1974, Appendix to C57.12.00-1973, Guide for Loading Mineral Oil-Immersed Overhead-Type DistributionTransformers with 55C or 65C Average Winding Rise; American National Standard C57.92-1962, Appendix toC57.12 Standards, Guide for Lo

29、ading Oil-Immersed Distribution and Power Transformers; and American NationalStandard C57.96-1959, Appendix to C57.12 Standards, Guide for Loading Dry-Type Distribution and PowerTransformers, respectively.2. Electrical Connections2.1 Primary and Secondary SystemsIn general, permissible transformer c

30、onnections are related to the type of service to be delivered and the type ofprimary supply.2.1.1 Types of ServiceThree-phase services may be 3-wire or 4-wire. The 3-wire service is quite commonly called “delta” service and consistsonly of three-phase conductors, having no neutral conductor. The 4-w

31、ire service is commonly called a “wye” service2 Copyright 1978 IEEE All Rights ReservedANSI/IEEE C57.105-1978 IEEE GUIDE FOR APPLICATION OF TRANSFORMERand includes a neutral conductor which is customarily grounded at the service for 208 Y/120 and 480 Y/277 V servicesand, if the supply originates out

32、side the building served, at one other point on the secondary side of the transformersupplying the system, either at the transformer or elsewhere. Some 4-wire services are derived from a -or open-connected secondary with the center tap of one leg grounded. This connection is commonly rated 240/120 V

33、, 3-phase,4-wire, and is also grounded in the manner described.2.1.2 Types of SourcesThe primary supply may be either an ungrounded, effectively grounded, or impedance-grounded source. Anungrounded supply may have a grounded shield wire or cable sheath, but such conductor should not be mistaken for

34、aneutral conductor if it is not intended for such service. The ungrounded supply is frequently called a delta () sourcebecause such systems generally consist of the three phase conductors only.The effectively grounded distribution system normally includes a solidly grounded neutral conductor derived

35、 from thesource. Usually the neutral is multigrounded along the feeder. Such systems are referred to as “grounded Y” systems.The impedance-grounded systems are usually found in industrial plant circuits operating at distribution voltage levelsof 4160 V and higher. Such systems may be Y or . If Y, th

36、e neutral is derived from the source, but is insulated andgrounded through a resistor or reactor. If , the grounding is through a grounding transformer to which an externalimpedance may or may not be connected. Such systems allow the flow of sufficient ground fault current to affordpositive high-spe

37、ed protective relaying, but limit the ground fault current in order to minimize damage to faultedequipment. Although the impedance-grounded Y systems are sometimes said to have a “floating neutral,” thisterminology is misleading. The neutral is actually stabilized at the source, and with fairly well

38、-balanced loads, theneutral voltage remains near ground voltage except during fault conditions.Figure 1 Quasi-Phasor and Y Connection DiagramsA, BY, CGrounded YIn the Y systems, the integrity of the neutral conductor is very important to proper z operation and safety.2.2 and Y ConnectionsIn both 3-p

39、hase transformers and banks of three single-phase transformers, the transformer windings are connectedeither phase-to-phase or phase-to-neutral in all but certain special connections (for example, the T connection). Whenthe windings are connected phase-to-phase as in Fig 1A, the quasi-phasor arrange

40、ment of the connection diagramresembles the capital Greek letter delta from which it gets the name and symbol . When the windings are connectedphase-to-neutral as in Fig 1B and C, the quasi-phasor connection diagram resembles the letter Y which is used as itssymbol. (The Y is inverted in the figure

41、so as to conform to its usual appearance in standard diagrams.) Y connectionsare also referred to as star connections, a more general term applicable to systems with any number of phases. Yconnections may have a grounded or ungrounded neutral. In this guide the term Y and symbol Y will represent the

42、ungrounded neutral connection, and the term Y-grounded and symbol YG will represent the grounded neutralconnection.Copyright 1978 IEEE All Rights Reserved 3CONNECTIONS IN THREE-PHASE DISTRIBUTION SYSTEMS ANSI/IEEE C57.105-1978Figure 2 Quasi-Phasor Zigzag Connection DiagramThe primary and secondary w

43、indings may be connected in any combination desired. However, certain combinationsmay be quite undesirable for a particular application. Table 1 shows all combinations of and Y connections andindicates the characteristics of each configuration which relate to its application. The connections which s

44、houldreceive special consideration to avoid misapplication are indicated to be “problem” connections.2.3 Zigzag-Connected WindingThe zigzag-connected winding has each electrical phase linked equally by two magnetic phases as shown in Fig 2.This winding connection is most commonly used in a single-wi

45、nding transformer to perform grounding duty. Theconnection presents a low-impedance path to ground for zero-sequence currents (that is, current components of equalmagnitude and phase angle in each leg), and therefore gound current flows with any shift of the system neutral.Grounding transformers may

46、 be sized so as to furnish only the magnitude of ground current required for relaying ormay be large enough to stabilize the neutral of an otherwise ungrounded system. In the latter case, the groundingtransformer supplies the unbalanced phase-to-neutral load as well as ground fault current.Table 1 A

47、pplication Characteristics of ConnectionsConnectionSuitable forUngrounded SourceSuitable for4-Wire ServicePhase ShiftHigh-Voltage to Low-Voltage(Note 1)Subject to PrimaryGrounding DutyTriple HarmonicPrimary Line CurrentsSuppressed“Problem”Connections(Note 2)Primary SecondaryYes No 0 No YesYes No 30

48、No YesYes Yes 30 No YesYes No 30 No YesYes No 0 No YesYes No 0 No Yes Note 34 Copyright 1978 IEEE All Rights ReservedANSI/IEEE C57.105-1978 IEEE GUIDE FOR APPLICATION OF TRANSFORMERNote 4 No 30 Yes Yes Note 4No No 0 No NoNo Yes 0 No No Note 5Yes No Note 6 No NoYes Yes Note 6 No NoNote 4 No Note 6 Ye

49、s No Note 4Note 4 Yes Note 6 Yes No Note 4Yes Yes 0 No YesYes Yes 30 No YesNo Yes 30 No NoNOTES:1 Based on standard connections and phasor diagrams.2 “Problem” connections are those connections which should receive special consideration to avoid misapplication.3 This connection is incapable of furnishing a stabilized neutral, and its use may result in phase-to-neutral overvoltage on one or two legs as a result of unbalanced phase-to-neutral load.4 Connections designated act as primary grounding transformers and should not