c57.109-1985

ANSIlIEEE C57.109-1985

An American National Standard

IEEE Guide for Transformer Through-Fault-Current Duration

Sponsor

Transformers Committee of the

Secretariat

Institute of Elec National Electri

Approved June 23,1983

IEEE Standards Board

Ap

American M

Copyright 1985 by

The Institute of Electrical and Electronics Engineers, Inc 345 East 47th Street, New York, NY 10017, USA

No part of this publication m a y be reproduced in any form, in an electwnic rehieVal system or ot&rwise,

without the prior written permission of the P M i a h e r .

Authorized licensed use limited to: Escuela Superior de Ingeneria Mecanica. Downloaded on March 13,2014 at 22:37:59 UTC from IEEE Xplore. Restrictions apply.

Foreword Foreword is not a part of ANSUIEEE C57.1091986, IEEE Guide for Transformer Through-Fault-Current Duration.)

ANSI C57.92-1962, American National Standard Guide for Loadiig Oil-Immersed Distribution and Power Transformers (Appendix to ANSI C57.12 standards) was issued in 1962. The guide contained a section entitled Protective Devices which provided information indicating the short-time thermal load capability of oil-immersed transformers. That information, of articular interest to those responsible for application of overcurrent protective devices for protection of transformers, is summarized as follows: B

Times Rated Time Current

2 s 25.0 10 s 11.3 30 s 6.3 60 s 4.75 5min 3 .O

30 min 2.0

During the revision activities o C57.92 it became evident that Times Rated Current cap&-ility of transformers as stated therein did not recognize the mechanical withstand considerations of transformers. Consequently, removed and considered separately.

In 1978, following particular urging b was formed under the auspices of the guide that would document the thou detail to facilitate CO the product of that workin

Since its issue in 1978 been incorporated in the ments for Liquid-Immerse but does not in any way supersede, ANSI/IEE)ff( C57.12.@1980.

Committee, a working group the assignment to prepare a of transformers in sufEcient

VIEEE C57.12.oOb-1978 has Standard General Require- rs. This guide supplements,

At the time it approved this standard, the C57 Committee had the following membership:

R E. Uptegraff, Jr, Chairman R L. Ensign, Vice Chairman

E Chyanization R e p m s d Name of Representcrtive Bonneville Power A m o n . . . . .................................................. Vacant Electric Light and Power Group ...................................................... N. Derwianka

R. L. Ensign I. H. Koponen B. F. Smith E. F. Vlllesuso, Jr J. P. Markey (AU)

0. Compton J. C. Dutton L. w. Long L S. McCormick W. J. Neiswender B. Stanleigh (AU)

Institute of Electrical and ElectroNca Engineers.. ...................................... J. V. Bonucchi


Cbganhtion Repmsented Name of Rqmentutive National Electrical Manufacturers Association ........... :. ............................. J. D. Douglaaa

W.C. Kendall K. R. Linsley W. J. McNutt H. Robin M. Sam@ R. E. Uptesraff, Jr R. J. Stahara (A&)

Naval Facilities E n g i n e e m Command ................................................ H. P. Stickley Rural ElechWcation Adminkmm 'on ................................................... J. C. Arnold, Jr Tennessee Valley Authority ........................................................... L. R. Smith Underwriters Laboratories ............................................................ T. O'Grady Water and Power Resources Service .................................................. F. W. Cook, Sr Western Area Power AdmhMrah 'on ................................................... D. R. Torgemn

R. W. Seelbnch (Alt)

At the time this guide was approved, the Working Group on Short Circuit Duration of the Perform- ance Characteristics Subcommittee of the Transformers Committee had the following membership:

W. F. Grif'fard, Chairman

E. J. Adolphson C. G. Evans J. W. McGill J. Alacchi D. A. GiUies C. J. McMfflen E. H. Arjeski A. W. Gofdman W. J. McNutt 0. R. Compton C. H. Gril3n E. W. Schmunk J. C. Dutton R. E. F. Troy J. A. Ebert M. D. A. Yannucci

E. T. Jauch

At the time this guide was approved the

0. R.

ance Characteristics Subcommittee were as follows:

E. J. Adolphson L. S. McCormick D. J. Allan C. J. McMillen E. H. Arjeski W. J. McNutt J. C. Arnold D. A. Roach J. J. Bergeron L. J. Savio J. D. Borst J. L. Harbell R. L. Schmid E. Chitwood C. N. Hendrickson D. S. Takach F. W. Cook E. L. Hook D. E. Truax D. A. Duckett C. P. Kappeler S. G. Vargo J. A. Ebert R. H. Kellogg R. A. Veitch C. G. Evans J. R. Woodall W. R. Farber W. E. Wrenn S. L. Foster D. A. Yannucci

At the time the IEEE Standard Board approved this guide on June 23, 1983, it had the following members:

James H. Beall, Chairmun Edward Chelotti, Vice Chairman Sava I. Sherr, Secretary

J. J. Archambault John T. Boettger J. V. Bonucchi Rene Castenschiold Edward J. Cohen Len S. Corey Donald C. Fleckenstein Jay Forster

'Member Emeritus

Donald H. Heirman Irvin N. Howell, Jr Joseph L. Koepfinger' Irving Kolodny George Konomos R. F. Lawrence John E. May Donald T. Michael'

John P. Rigamti FrankL.ROtW3 Robert W. Seelbach Jay A. Stewart Clifford 0. Swanson Robert E. Weiler W. B. Wilkens Charles J. Wylie

T


Contents

SECI'ION PAGE

1 . Scope .................................................................................. 7 2 . Purpose ................................................................................. 7 3 . General ................................................................................. 7 4 . References .............................................................................. 7 5 . Transformer Coordination Curves ......................................................... 8

5.1 Category I Transformers .............................................................. 8 52 Category 11 Transformers ............................................................. 9 53 Category III Transformers ............................................................. 10 5.4 Category IV Transformers ............................................................. 11 5.5 Recommended Duration Limit Summary ................................................ 11

FIGURES

Fig 1 Category I Transformers ............................................................. 8 Fig 2 Category 11 Transformers ............................................................ 9 Fig 3 Category III Transformers ........................................................... 10 Fig 4 Category IV Transformers ........................................................... 11 TABLE

Table 1 Minimum Nameplate Kilovoltamperes ............................................... 12


An American National Standud

IEEE Guide for Transformer Through-Fault-Current Duration

1. scope the frequency of fault occurrence is high. The point of transition between mechanical concern and thermal concern cannot be precisely defined,

This guide applies to transformers referenced but mechanical effects tend to have a more prominent role in larger kilovoltampere ratings, because the mechanical stresses are higher.

in ANSIlIEEE C57.12.00-1980 [2] as Categories I, 11, III, and IV.

4. References 2. Purpose

transformers that relate duration and fault magnitude to withstand capability.

This guide sets forth recommendations be- lieved essential for the application of overcurrent protective devices applied to limit the exposure time of transformers to short-circuit current (see ANSIlIEEE C37.91-1985 [l]). This guide tended to imply overload capability.

3. General

The magnitude and duration of fault current are of utmost importance in establishing a coor- dinated protection practice for transformers as both the mechanical and thermal effects of fault current should be considered. For fault-current magnitudes near the design capability of the transformer, mechanical effects are more signifi- cant than thermal effects. At low, fault-current

When the following American National Stand- ards referred to in this guide are superseded by a

ion approved by the American National Standards Institute, Inc, the latest revision shall apply:

111 ANSIIIEEE C37.91-1985, IEEE Guide for Pro- tective Relay Applications to Power Transfor- mers.

121 ANSIlIEEE C57.12.00-1980, IEEE Standard General Requirements for Liquid-Immersed Dis- tributtm, Power, and Regulating Transformers.

[31 AlUSIlIEEE C57.91-1981, IEEE Guide for Loading Mineral-Oil-Immersed Overhead and Pad- Mounted Distribution Transformers Rated 500 kVA and Less with 65 "C or 55 "C Average Winding Rise.

[4] ANSIlIEEE C57.92-1982, IEEE Guide for Loading Mineral-Oil-Immersed Power Transfor- mers up to and Including 100 MVA with 55C or 65C Wmding Rise.

[5] IEEE Std 766, IEEE Trial-Use Guide for Load- ing Mineralail-Immersed Power Transformers Rated in Excess of 100 MVA (65C Winding Rise).

magnitudes approaching the overload range, mechanical effects assume less importance unless These documents are available from lEEE Senrice Cen-

ter, 446 Hoes Lane, Piscataway, NJ 08864. Copies of these documents are also available from the Sales Department, American National Standards Institute, 1430 Broadway, New York, NY 10018.

The numbers in brackets correspond to the numbers of the references in Section 4.

7


ANSIDEEE C67.1091986

02

0.1

5. Transformer Coordination Curves

CURRENT IN TIMES NORMAL BASE CURRENT

1- I211 (ANSVIEEE C57.12.00- - 0.2

0.1

For purposes of coordination of overcurrent protective devices, Figs 1, 2, 3, and 4 are pre- sented as protection curves for different size transformers. For Categories I and IV, single curves apply which reflect both thermal and mechanical damage considerations. For Categories I1 and HI, double curves apply, one of which reflects both thermal and mechanical damage considerations, while the other reflects primarily thermal damage considerations. On curves which have both a solid and a dashed portion, the solid portion represents a total fault duration beyond which thermal damage may occur in insulation

IEEE GUIDE FOR TRANSFORMER

macent to current-carrying conductors, while the dashed portion represents a total fault duration beyond which cumulative mechanical damage may occur. The increasing significance of mechanical effects for higher kilovoltampere transformers is reflected in these curves. The va- lidity of these damage limit curves cannot be demonstratecl by test, since the effects are pro- gressive over the transformer lifetime. They are based principally on informed engineering judg- ment and favorable, historical field experience.

5.1 For Category I Transformers. The recommended duration limit is based on the curve of Fig 1. The curve reflects both thermal and me-

Fig 1 Category I Transformers

IO OOO IO 000

5000 5000

2000 2000

1000 1000

500 500

200 200

I 100 100

s

c In In n

g 5 0 5 0 2 8 E 20 20 y VJ

W c - c-

TIMES NORMAL RASE CURRENT

a


THROUGH-FAULTCURRENT DURATION

1

O.5

02

0.1

ANSIDEEE C67.1091B6

- FOR FAULT CURRENT FROM 70% TO . I . 0.5

100% OF MAXIMUM POSSIBLE: P t = K

Z = SYMMETRICAL FAULT CURRENT IN TIMES NORMAL BASE CURRENT

-WHERE

- (ANSVIEEE C57.12.00-1980) ' 0.2 K = CONSTANT DETERMINED AT

MAXIMUM I WITH t = 2 SECONDS

chanical damage considerations and should be applied as a protection curve for faults which will occur frequently or infrequently.

5.2 For Category I1 Transformers. The recommended duration limits depend upon fault frequency and are based upon the curves of Fig 2. Fault frequency refers to the number of faults with magnitudes greater than 70% of maximum.

5.2.1 The left-hand curve, reflecting both thermal and mechanical damage considerations, should be applied as a protection curve for faults which will occur frequently (typically more than 10 in the life of a transformer). It is dependent

upon impedance of the transformer for fault current above 70% of maximum possible and is keyed to the 1% of the worskase mechanical duty (maximum fault current for 2s).

5.2.2 The righGhand curve reflects primarily thermal damage considerations. It is not dependent upon impedance of the transformer and may be applied as a protection curve for faults which will occur only infrequently (typically not more than 10 in the life of a transformer). This curve also may be used for backup protection where the transformer is exposed to frequent faults nor- mally cleared by high-speed relaying.

9


ANSIlIEEE CS7.1091986 IEEE GUIDE FOR TRANSFORMER

5.3 For Category I11 Transformers. The recommended duration limits depend upon fault frequency and are based upon the curves of Fig 3. Fault frequency refers to the number of faults with magnitudes greater than 50% of maximum.

5.3.1 The lef&hand curve, reflecting both thermal and mechanical damage considerations, should be applied as a protection curve or faults which will occur frequently (typically more than 5 in the life of a transformer). It is dependent upon impedance of the transformer for fault current above 60% of maximum possible and is

keyed to the 1% of the worst-case mechanical duty (maximum fault current for 2s).

5.3.2 The righGhand curve reflects primarily thermal damage considerations. It is not dependent upon impedance of the transformer and may be appJied as a protection curve for faults which will occur only infrequently (typically not more than 5 in the life of a transformer). This curve also may be used for backup protection where the transformer is exposed to frequent faults nor- mally cleared by high-speed relaying.

Fig 3 Category I11 Traneformers

'Thlscuwe may also be used for backup

r = SYMMETRICAL FAULT CURRENT IN TIMES NORMAL BASE CURRENT

TIMES NORMAL BASE CURRENT

10

-~ i i


THROUGH-FAULT-CURRENT DURATION

5 -

2.

1

05

02

ANSIAEEE C67.1091986

1 \ \\.i\,\ ' \ \ \ \ \

~5 \\\\ !\ \ '\

\ \ \ \\ \\ \\\\\\ \

- 2 12 I0876 5 4

X TRANSFORMER IMPECUNCE -FOR FAULT CURRENT FROM 50% TO

-WHERE 0.5

- 1 10046 OF MAXIMUM POSSIBLE: P t = K

I = SYMMETRICAL FAULT CURRENT IN TIMES NORMAL BASE CURRENT

' 0.2 - (ANSIIIEEE C57.12.00-1980) K = CONSTANT DETERMINED AT

-0 I MAXIMUM I WITH t = 2 SECONDS

5.4 For Category IV Transformers. The recommended duration limit is based upon the curve of Fig 4. The curve reflects both thermal and mechanical damage considerations and should be applied as a protection curve for faults which will occur frequently or infrequently. It is dependent upon impedance of the transformer for fault current above 50% of maximum possible

and is keyed to the 1% of the worst-case mechanical duty (maximum fault current for 2s).

5.5 Recommended Duration Limit Summary. Recommended duration limits designated for transformers given in ANSI/IEEE C57.12.00-1980 [2] as Categories I, 11, 111, and IV are as given in Table 1.

Fig 4 Category IV Transformers

2 5 IO 20 50 TIMES NORMAL BASE CURRENT

11


ANSIWEE C67.1091986

Table 1 Minimum Nameplate Kilovoltamperes

~ ~ ~ _ _ _ _ ~ _ _ _ _ _ ______ ~~~

Reference Protection Curves. C*gw S i e Phase Three Phase

I 6to500 16 to 500 Fig1 n 601 to 1667 601 to M)oo Fig2 III 1668tolOOOO 5001tO3OOOO Fig 3 N above 10 OOO above 30 OOO F i g 4

'NOTE: In Figs 1,2 ,3 , and 4 the Times Normal Base Current Scale relates to minimum nameplate kilovoltamperes. Low values of 3.5 or less Times Normal Base Current may result from overloads rather than faults and for such cases, loading guides may indicate allowable time durations dflerent from those given in Figs 1 through 4. See ANSIlIEEE C57.91-1981 [3] and ANSI/IEEE C67.92-1982 141.


1 Scope2 Purpose3 General4 References5 Transformer Coordination Curves5.1 Category I Transformers52 Category 11 Transformers53 Category III Transformers5.4 Category IV Transformers5.5 Recommended Duration Limit Summary

Fig 1 Category I TransformersFig 2 Category 11 TransformersFig 3 Category III TransformersFig 4 Category IV TransformersMinimum Nameplate Kilovoltamperes

c57.109-1985

Documents

c57 committee

ansi c57

ansuieee c57

ansiieeff c57

ansilieee c57

immersed transformers

protection of transformers

time current