C37 012-Ieee PDF

 

ANSI/IEEE C37.012-1979

A n American Nat National ional Standa Standard rd

IEEE Application Guide for

Capacitance Current Switching for A C High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis Sponsor

Switchgear Committee of the IEEE IEE E Power Engineering Society S ociety Approved June 2,1977

IEEE Standards Board

Secretariat

Institute of Electrical and Electronics Engineers National Electrical E lectrical Manufacturers Association

Approv App roved ed Se Septem ptember ber 16 , 19 77

American Ameri can National Standards Institute

Published by

Institute of Electrical and Electronics Engineers, Inc 345 East 47t 47th h Street, New New York, N.Y. 10017

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.

 

American National Standard An Am er i can Nat i o n al S t an d ar d i m p llii es a co n s en s u s

of t h o s e s u b -

s t an t i a l l y co n cer cern n ed wi t h i t s s co p e an d p r o v i s iio o n s . An Am er i can Nat i o n al S t a n d a r d i s i n tte e n d e d a s a g u i d e to a i d t h e m a n u f a c t u r e r , t h e c o n s u m e r , an d t h e g en er a all p u b l i c. T h e ex i s t en ce of a n Am er i can Nat i o n al S t a n d a r d d o es n o t i n an y r es p ect p r ec ecll u d e an y o n e, wh et h er h e h a s ap p r o v ed t h e s t a n d a r d or n o t , f r o m m a n u f a c t u r i n g , m a r k e t i n g , p u r c h a s i n g ,

or using

p r o d u ct s ,

s t an d ar d .

p r o ces s es ,

or

p r o ced u r es

not

co n f o r m i n g

to

the

Am er i can Nat i o n a l S t an d ar d s ar e s u b j ect t o p er iio o d ic ic r ev iew iew an d u s er s a r e c a u t i o n e d t o o b t a i n t h e l a t e s t e d i t i o n ss..

CAUTION NOTICE: T h i s A me me r i ca ca n N a t i o n a l S t a n d a r d m a y b e of t h e Am er i can

r ev i sed sed o r wi t h d r awn a t an y t i m e. T h e p r o ced u r es

N a t i o n a l S t a n d a r d s I n s t i t u t e r e q u iirr e t h a t a c t i o n b e t a k e n t o r e a ffff i rm rm , r ev i se, se, o orr wi t h d r aw t h i s s t an d ar d n o l at er t h a n f iiv v e y ear s f r o m t h e d at e of of p u b l i cat i o n . P u r ch as er s of of Am er i can Nat i o n al S t a n d a r d s m ay r ecei v e cu r r en t i n f o r m at i o n o n al l s t an d ar d s b y cal l i n g o r wr i t i n g t h e A m e r ic ic a n N a t i o n a l S t a n d a r d s I n s t i t u t e .

0

Copyright 1 9 7 9 by

The Institute Institu te of Electrical and Electronics Electronic s Engineers, Inc N o p a r t of hi s p ub l i c a t i o n m a y b e re re p r o duc duc e d i n a ny f o r m ,

in an electronic retrieval system or o t he r wi s e , wi t ho ut t he p r i o r wr i t t e n p e r m is is s i o n o f t he p ub l i s he r .

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

Foreword (This Foreword is not a part of ANSI/IEEE C37.012-1979, American National Standard Application Guide for Capacitance Current Current Switching for AC High-Voltage Circuit Breakers Breakers Rated o n a Symmetrical Current Basis.)

The development of standards for the rating, testing, and manufacture of high-voltage circuit breakers began almost simultaneously simultan eously with the application applicatio n of th the e first circuit breakers in early power supply systems. A number of engineering and manufacturers trade organizations were interested in standards for high-voltage circuit breakers as well as other types of electrical equipment and worked to develop standard requirements re quirements f or capabilities, capabilities, sizes, sizes, and tes ting procedures. procedures. Among these groups were th e AIEE’,, th e National Electric Light Associatio AIEE’ Association n (NELA), th e Electric Power Club (a predecessor predecessor of NEMA - he National Electrical Manufacturers Association), the Association of Edison Illuminating Companies Companies (AEIC), and t he Edison Electric Insti tute (EEI). During the years up to 1940, these organizations adopted and published a number of standardization proposals proposals concerning rating, testing, and oth er requirements require ments fo r high-volta high-voltage ge circuit breakers. In 1941, a unified series of standards for circuit breakers, based on those of AIEE, AEIC, and NEMA, NE MA, were published fo r trial use by th e American Standards Standard s Association (ASA). This comprised the first American Standard for high-voltage circuit breakers. In 1945, this series was issued as an approved American Standard with th e familiar C37 number identification. This series included included sections on rating, preferred sizes, sizes, testing, and application application of circuit breakers. breakers. In 195 2 and 1 95 3, this series of of standard s was revised revised and supplemented by additional sections, sections, forming the complete, basic gr oup of American Stan dards f or high-volt basic high-voltage age circuit breakers. breakers. A t the time of publication this group of standards standa rds included: ANSI C37.4-1 C37 .4-1 953

AC Power Circuit Breakers (included (include d definitions, definitio ns, rating basis, and some test requirements)

ANSI C37.5-1953

Methods for Determining the RMS Value of a Sinusoidal Current Wave and Normal-Frequency Recovery Voltage, Voltage, and f or Simplified Simplified Calculation Calculation of Fault Currents

ANSI C37.6-1953

Schedules of Preferred Ratings for Power Circuit Breakers

ANSI C37.7-1952

Interrup ting Rating Factor s fo r Reclosing Reclosing Servi Service ce

ANSI C37.8-1952

Rated Control Voltages and their Ranges

ANSI C37.9-1953

Test Code fo r Power Circuit Circuit Breakers Breakers

ANSI C37.12-1952

Guide Specifications for Alternating Current Power Circuit Breakers

Under these original standards, the basis of the interrupting rating was established by 6.11 of ANSI C37.4-1953 as the highest current to be interrupted at the specified operating voltage and was the “. . . rms value including the dc component at the instant of contact separation as determined from t he envelope envelope of th e cu rren t wave.” wave.” Since Since this standard based th e interrupti ng rating rating on the total current includin including g dc component component at the instant of contact separation, it has become become known Basis of of Rating.” as th e “Total Current Basis For circuit breaker application, a simplified method was available in ANSI C37.5-1953, which listed liste d multiplying factors for use with the system symmetrical fault curr ent t o derive derive a maximum possible total rms current which could be present at contact separation. This current was used to choose the required circuit breaker rating from those listed in ANSI C37.6-1953, or subsequent revisio revi sions. ns. The fac tors recognized recognized typ ical system characteristics and circuit breaker operating times. times.

‘AIEE (American (American Institute o f Electrical Electrical Enginee Engineers) rs) m merged erged with IRE (Institu te of Radio Engineers) January 1 , 1 9 6 3 to form the joint organization organization IEEE (Institut e of Electri Electrical cal and Electronics Engineers). Engineers).

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

In 1951, th e AIEE Swi Switchg tchgear ear Committe Committee e began to gi give ve consid considerati eration on t o th e develop development ment of a circuit breaker rating method based on symmetrical interrupting currents. This work was initiated with wit h the goal of: clearing ng circuit breakers are used (1) Simplifying application where high-speed relaying and fast cleari (2) Bringing American standards into closer agreement with accepted international standards (IEC-International Electrotechnical Commission) Commission) t o avoid confusion on rating differences proven oven to demon strate a definite relationship between (3) Requiring th at circuit breakers are pr asymmetrical interrupting capability and symmetrical ratings During th e course of this work, principall principally y in a working working group of th e AIEE Power Circ Circuit uit Breaker Suhcommittee, numerous reports of the proposals on the new rating, testing, and application methods were made t o t he industry as a whole through committee sponso sponsored red paper paperss at AIEE meet meet-ings in 1954, 1959, and 1960. Suggestions made in discussions were considered by the working group and incorpo rated where prac practicabl ticable. e. The principal principal change from th e 1953 “Total Current” standar d wps in t he basi basiss of rating. 4.5.1 of ANSI C37.04 estab establishe lished d th e Rated Shor t Ci Circuit rcuit Current as “the highest value of the symmetrical component of the.. . short-circuit current in rms amperes,, meas amperes measured ured from th e envel envelope ope of th e curre nt wav wave e a t con tact separation, separation, whic which h the circuit circuit breaker is required required to interru pt at rated maximum voltage.. .”. Certain related capabilities were also required, including including oper ation under specif specified ied conditions of asymmetry based on typical circuit characteristics and circuit breaker timing. This rating structure became known as the Symmetrical previouss Total Current Ba Current Basis of Rating as compared to the previou Basis sis of Rating. However, as the new ratings ratings were develo developed, ped, it beca became me apparent t ha t chan changes ges from the older to th e newer newer standa standard rd could not occur overnight due to requirements for rerating and retesting of many PCBs. It was, therefore, decided to retain rating structures, the understanding that circuit circuit all new breaker developments would both be directed toward thewith standards. The breakers symmetrical based on the total current standards would be trans transferred ferred t o th e new standards as wo work rk prog progress ressed ed in rerating programs. This transfer is being carried out and ANSI C37.6 and ANSI C37.06 have been revised accordingly a number of times. The symmetrical current group of sta ndard sections was publis published hed in 1 96 4 and was gi given ven ANSI ANSI C37.04, C37.05, C37.06, etc, designatio designations. ns. These sections and th e corresponding 1 9 5 3 sections were : Total Current Standard

Symmetr Symmetrical ical Current Standard

Subject

ANSI C37.4

ANSI C37.03 ANSI C37.04 ANSI C37.04a

Definitions Rating Structure

ANSI C37.5

ANSI C37.05

Measurement of Voltage and Current Waves

ANSI C37.6

ANSI C37.06 ANSI C37.06a

Preferred Ratings

ANSI C37.7

ANSI C37.07

Reclosing Factors

ANSI C37.8

(included in

Control Voltage Voltagess

ANSI C37.06)

ANSI C37.9

ANSI C37.09 ANSI C37.09a

Test Code

ANSI C37.5 (Section 3)

ANSI C37.010

Application Guide (expansion of material previously in C37.5)

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

Sections .04a, .06a, and .09a, also issued in 1964, were addenda concerned with supplemental dielectric dielect ric capability capability req uirements. In ANSI C37.06-1964 and subsequent revisions prior to 1971, circuit breaker symmetrical current interrupting ratings were derived from ratings in ANSI C37.6-1961 by a relationship following a middle midd le ground position position bet between ween t he to tal (asymmetrical) (asymmetrical) current of th e former rating rating method and the f ull range of related requir ements of t he new rating method. For a give given n breaker this derivation was expressed by the formula: nominal voltage rated short circuit current

where

=

1 1 9 6 1rated maximum voltage

I

=

interru pting rating in amperes ampe res appearing in ANSI C37.6-1961 C37.6-1961

F

=

0.915 for 3 cycle breakers 0.955 for 5 cycle breakers 1.0 for 8 cycle breakers

Rated short circuit current was tabulated for rated maximum voltage rather than for nominal voltage as had been been th e case under th e total curren t basis basis of rating. rating. It was stressed that this derivation was for the numerical conversion only and that a given circuit breaker, designed and tested under t h e total c urrent basis basis of of rating, could not be assumed t o have these capabilities capabilities under the symmetrical current basis basis of rating withou t approval of the manufacturer. In th e revision revision of ANSI C37.06 C37.06 published in 197 1, several several simplificati simplifications ons were intro duced, including the use of a new method for select selection ion of interrupting cu rrent ratings ratings fo r outdo or circuit circuit b break reakers ers 1 2 1 kV and above. Values fo r rated sh ort circuit curre c urre nt were chosen from th e R-10 preferred number series, and th e use of a reference nominal 3-phase MVA identification identification was discontinued. Also Also th e rated voltage voltage range range factor K was changed changed t o unity, 1.0, t o simplify rating and testing procedure procedures. s. In the intervening years since the official publication of the primary sections of the symmetrical basiss of rating stand ard fo r high-voltage basi high-voltage circuit breakers, a number of revisions, revisions, additions, and improvements have been developed and published. Many of these additions were in subject areas of major imp ortance ortanc e in th e rating, testing, and application of circuit breakers and were published published as complete standards containing appropriate definitions, rating performance criteria, rating numbers, test procedures, and application considerations. considerations. This was done t o avoid avoid delay delay in publication an d th e necessity of reprinting other existing standards as each of these was completed. The result has been the publication of a substantial number of individual supplementary standards. The basic subject areas considered in these supplementary standards, and their initial publication dates, are shown below: ANSII C37.071 -1969 ANS

Requirements fo r Line Closing Closing Switching Switching Surge Control

ANSI C37.072-1971

Requirements for Transient Recovery Voltage

ANSI C37.0721-1971

Application Guide for Transient Recovery Voltage

ANSI C37.0722-1971

Transient Recovery Voltage Ratings Ratings

ANSI C37.073-1972

Requirements for Capacitance Current Switching

ANSI C37.0731-1973

Application Guide for Capacitance Current Switching

ANSI C37.0732-1972

Preferred Ratings fo r Capacitance Curren t Switching Switching

ANSI C37.074-1972

Requirements for Switching Impulse Voltage Insulation Strength

ANSI C37.076-1972 ANSI ANSII C37.078- 1972 ANS

Requirements for Pressurized Components Requirements for External Insulating

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

ANSI C37.0781-1972

Test Values for External Insulation

ANSI C37. 079-1 079-1973 973

Method of Testing Circuit Circuit Breakers When When Rated for Out-of-Phase Switching

A goal goal of work recently completed, and represented by t he 197 9 publication o off these standards, has been the editorial incorporation of all th e supplemen supplementary tary standards listed listed above into th e proper primary standards documents. For circuit break breakers ers rated o n a symmetr symmetrical ical current basis, basis, th e consolidated stan dards sections are: ANSI/IEEE C37.0 C37.0 4-19 79

Rating Structure

ANSI C37.06-1979

Preferred Ratings and Related Required Capabilities

ANSI/IEEE C37.09-197 C37.09-1979 9

Test Procedure

ANSI/IEEE C37.010-1979

Application Guide - General

ANSI/IEEE C37.011-1979

Application Guide -

ANSI/IEEE C37.012-1979

Application Guide - Capacitance Current Switching

ransient Recovery Voltage

The present ANSI C37.05, Measurement of Current and Voltage Waves, is incorporated into ANSI/IEEE ANSI/IE EE C37.09; ANSI C37.07, Interrup Int errupting ting Capability C apability Fact Factors ors fo r Reclosing Service, is incorporated porat ed in to ANSI/IEEE ANS I/IEEE C37.04, ANSI C37.06, and ANSI/IEEE C37.09. C37.09. Definitions which have been are now C37.100-1972. in C37.03-1964 in ANSI Standards are presently being developed in a number of additional subject areas, which will be initially published published as supplementary standards and incorporated in to the primary primary subject document at some future date. Included among these subjects are requirements for current transformers, a guide for synthetic testing, sou nd level measurements, and seismic seismic cap capability ability requirements. For circuit breakers still rated on a total current basis, as listed in ANSI C37.6, the existing standards stan dards ANSI C37.4, ANSI C37.6, C37.6, ANSI C37.7 C37.7,, and ANSI C37.9 will continue t o be applicable. Documents pertaining to guide specification and control schemes, which apply to both groups of ratings, rati ngs, are included in t he ANSI C37 series series as shown below: ANSI C37.11-1972

Requirements for Electrical Control on AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis Basis and a Total Current Basis Basis

ANSI C37.12-1969

Guide Specifications for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis and a Total Current Basis

Periodic review of all these standards takes place through the normal ANSI procedure that standards are reaffirmed, revised, or withdrawn within no more than five year intervals from the original orig inal publ publication ication date. Suggestions for improvement gained in the use of this thi s stan dard will be welcome. They should be sentt to th e sen American National Standards Institute 1430 Broadway New York, N Y 10018 The basic basic data included in this consolidated do cumen t is the result of contributions made by many individuals over many years. A t th e time of appr approval, oval, however, the th e American National

Authorized licensed licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

Standards Committee on Power Switchgear, C37, which reviewed and approved this standard, had the following personnel:

J. P. Lucas, Secretary

C. L. Wagner, Chairman

J. E. Beehler, Executive Vice-chairmano f Hig Highh- Voltage Switchgear Standards W. E. Laubach, Executive Vice-Chairmanof Low-Voltage Switchgear Switchgear Standa Standards rds W.

R. Wilson, Executive Vice-chairmanof IEC Activities

Organization Organiz ation Represented

Name of Representative

. . . . . . . . . . . .. . . . . . . . . . . .. . . . . . . . . ........................................

Association of Iron and Steel Engineers.

J. M. Tillman

Electric Light

J. ,E. Beehler

Power Gro up

Institute of Electri Electrical cal a nd Electronics Enginee Engineers rs

............................

H. G. Darron H. G. Frus K. D. Hendrix F. R. Solis K. G. Adgate (Alt) R. L. Capra (Alt) R. L. Lindsey (Alt) E. E. Ramm (Alt) M. J. Maier H. H. Fahnoe R. E. Friedrich G. W. Walsh H. F. White M. J. Beachy (Alt) C. A. Mathews (Alt) R. A. McMaster (Alt) D. C. Musgrave (Alt)

National Electrical Manufacturers Association.

Testing Testi ng Laboratory Group.

.............................

..........................................

......................................... U.S. Department of the Army . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tennessee Tenness ee Valley Valley Auth ority.

...................... Facilities Engineering Command . . . . . . . . . . . . . .

A. P. Colaiaco R. W. Dunham D. G. Portman G. A. Wilson W. R. Wilson E. J. Huber R. A. Naysmith R. W. Seelbac Seelbach h (Alt) R. C. St. Clair R. H. Bruck

U.S. Department of the Interior, Bureau of Reclamation.

E. M. Tomsic

U.S. Department of the Navy, Naval

D. M . Hannemann

The personnel of the C37 Subcommittee on High Voltage Circuit Breakers which reviewed and approved approv ed this do cume nt were as follows: F. G . Schaufelberger, Chairman

J. J. Fayed, Secretary J. E. Beehler D. 0 . Craghead

M. A. Durso C . J. Dvorak R. E. Friedrich R . D.Hambnck

D. R. Kanitz W. E. Laubach G. N. Lester F. W. mith D. L. Swindler W. R . Wilson

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC UTC from IEEE Xplore. Restrictions apply.  

The basic Application Application Guide was prepared by a Working Working Group o n Standard s for Capacit Capacitance ance Current Switchi Switching ng of of t he IEEE High-Vol High-Voltage tage Power Circuit Breaker Breaker Su bcomm ittee of th e IEEE Switchgear Switchg ear Committee. T he personnel of t he Working Group were as follows:

V . E. Phillips, Chairman J. E. Beehler

N . E. Reed

F. G. Schaufelberger

R. G. Colclaser C. F. Cromer

W. H. Shafer

G. N. Lester

B. F. Wirtz

When the IEEE Standards Board approved this standard on June 2,1977, it had the following membership:

Irvin N . Howell, Jr, Vice Chairman

W. R. Kruesi, Chairman Ivan G . Easton, Secretary William E. Andrus Jean Jacques Archambault Mark Barber Edward J . Cohen Warren H. Cook Louis Costrell R. L. Curtis David B. Dobson

R 0. Duncan

Charles W. Flint Jay Forste Forsterr Ralph L Hauser Joseph H. Koepfinger Irving Irvin g Kolodn y Benjamin J. Leon Thomas . Martin

Donald T. Michael Voss A. Moore William S. Morgan William J. Neiswender Ralph M. Showers Robert A. Souderman Leonard W. Thomas, Sr B. W. Whittington

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

Contents SECTION

...................................................................

PAGE

1

Scope

2

Purpose ..................................................................

11  11 

3

General Application Conditions

11  11 

4

Capacitance Current Switching Appl Capacitance Application ication Considerations 4.1 Maximum Voltage for Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Frequency .......................................................... 4.3 Capacitance Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Interrupting Time 4.5 Transient Overvoltage 4.6 Open Wire Transmission Lines 4.7 CapacitorBanks ...................................................... 4.8 Cables .............................................................. 4.9 Switc Switching hing Through Transformers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Unusual Circuits . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . .... . . . . . . . . . . . . . . .... . . . . . . . 4.10 4.11 EffectofLoad . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.12 Effect of Reclosing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.13 Resistor Thermal Limitations . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . 4.14 Current Pause Method

11  11  11  11  11  11  11  11  11  11  11  11  13  13  15  15  22  22  27  27  27  27  30  30  30  30  31  31  31  31 

Considerations of Capacitance Currents and Recovery Voltages Under Fault Conditions . . . . 5.1 Reasons for Successful Circuit Breaker Operation 5.2 Switching Open Wire Transmission Lines Under Faulted Conditions . . . . . . . . . . . . . . 5.3 Switching Capacitor Banks Under Faulted Conditions 5.4 Switching Cables Under Faulted Conditions 5.5 Requirements 5.6 Examples of Application Alternatives

31  31  31  31  31  33  33  33  33  33  33  34  34 

............................................... ..........................

..................................................... .................................................. ...........................................

.................................................

5

............................

......................... ................................. ........................................................ ......................................

6

Revision.of Revis ion.of American American National Standards Referred t o in this D ocument

7

References

11  11 

. . . . . . . . . . . . . . . . 34  34 

...............................................................

34  34 

FIGURES

Fig 1

RMS RM S Charging Current Versus Sy stem Voltage fo r Single-Conductor and Two-Conductor Bundle Lines Typical Current and Voltage Relations for a Compensated Line Fig 3 2 First Half-Cycle of of Recovery Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig Typical Circuit for Back-to-Back Switching ................................ Fig 4 Example 115 kV System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig 5 Typical.Circui Typical. Circuitt for Back-to Back-to-Back -Back Switching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig 6 Back-to-Back Cables .................................................. Fig 7 Bank-to-Cable Switching Circuit ........................................ Fig 8 Equivalent Bank-to-Cable Switching Circuit ................................ Fig 9 Fig 10 Voltage Voltag e and Current Relations for Capacitor Switching Through Interposed Transformer ........................................ Fig 11 Station Illustrating Large Large Transient Inrush Currents Through Circui Circuitt Breaker Breakerss fr om Parallel Capacitor Banks ...................... Fig 12A Recovery Voltage and Current for Last Phase to Clear When Faulted Phase Is First in Sequence to Clear ........................... Fig 12B Recovery Voltage and Current for First Phase t o Clear When Faulted Phase Is Second in Sequence to Clear .........................

.........................

12  12   15  15  15  . . . . . . . . . . . . . . . . 15  18  18   20  20  24  24  24  24  26  26  26  26 

28  28 

29  29  32  32  32  32  

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

PAGE

TABLES

Table 1 Table 2 Table 3 Table 4

................. ..................... .............................. ...................

Inrush Current and Frequency for Switchin Switching g Cap acitor Banks Typical Values of Inductance Between Capacitor Banks. Frequency and Current Amplitude Relations Recovery Voltages and Currents on Unfaulted Phases of 242 kV Open Wire Transmission Line with a Phase-to-Ground Fault

Table Table Table Table

19  25  

35 35  

36  . . . . . . . . . . . . . . . . . . . 36  . . . . . . . . . . . . 37   . . . . . . . . . . . . 38  38  .............................. 39  39  40  ......................... ......................... 4 1  

Table 5 Table

17 

Recovery Voltages and Currents o n Unfaulted Phases of 550 kV Open Wire Transmission Line with a Phase-to-Ground Fault Recovery Voltages and Currents Curre nts on Unfaulted Unfa ulted Phases of of 242 kV 6 Open Wire Transmiss Transmission ion Line with a Phase-to-Phase Phase-to-Phase Grounded Fault Recovery Volt Voltages ages and Currents on Unfaulted Phases of 5 50 kV 7 Open Wire Wire Transmission Transmission Line with a Phase-to-Phase Phase-to-Phase Grounded Fault 8 Recovery Voltages and C urrents on Unfaulted Balanced Shunt Capacitor Bank (Reference Condition) Recovery Voltages Voltages and Currents o n Unfaulted Phases of Shunt 9 Capacitor Capacit or Bank with with Fault t o Neutral o n One Phase Phase 1 0 Recovery Voltages and Currents on Unfaulted Phases of Shunt Capacitor Bank with Fault to Ground on One Phase

APPENDIXES

43  .................... Appendix B Bas Basic ic Relations During Capacitance Capacitance Current Switch ing. ..................... 44 55    B1. Capacitance Current Switching Rating ....................................... B2. Investigation of Transient Currents When Energizing ............................ 45  B2.1 Energizing Energizing Capacitor Banks ........................................... 45   B2.2 Energizing Energizing Lines or Cables ........................................... 47  47   B3 . Investi Investigation gation of Overvoltages Overvoltages Occurring When When Interruptin Inte rruptin g Capacitor Bank Current ................................................... 48  B3.1 Capacitor Overvoltage Overvoltage from a Single Single Restrike Through the Primary Arching Contacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48  B3.2 Voltage from Two Restrikes Restrikes Through th e Primary Arching Arching Contacts, Each After a Current Pause of 180" ............................ 48  B3.3 Overvoltage Overvoltage from Restrikes Through th e Secondary (Resistor) ArchingContacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49   Transmission ion Line Switching Switching Double Restrike Through Resistor Resistor . . . . . . . . . . . . . . . . . . 50  50   B4 . Transmiss

Transmission ion Cu rrent Calculation Calculation Appendix A Example of Open W i r e Transmiss

FIGURES

FigAl Fig B1 Fig B2 Fig B3 Fig B4 Fig B5

.................................................................... ............................. ............... ............................ ............................. ......................... .......... ....................................................................

. . . . . . . . . . . . . .. . . . . . . . . . . . . . . .... . . . . . . . . . . . . . .... . . . . . . . . . . . . .... . . . . . . . . . .

....................................................................

............................. ............... ............................ ............................. ......................... ..........

44  46   47  47   48  49  

51  51 

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictio ns apply.  

A n American National Standard IEEE Ap Applicati plication on Guide for

Capacitance Curr Curren entt Sw Switch itching ing for ACon H igh-V High-V oltage Circuit Breakers Rated a Sym S ymm m etrical Cu Curr rrent ent Basis 1. Scope

maximum volt voltage age since thi s is th e upper limit for operation.

This application guide guide for capacitance curren t switching applies to ac high-voltage circuit breakers rated in accordance with ANSI/IEEE C37.04-1979, Rating Structure for AC HighVoltage Circuit Breakers, and listed in ANSI C37.06-1979, Schedules of Preferred Ratings and Related Required Capabilities for AC High High-Voltage Circuit Breakers Rated on a Symmet-

4.2 Frequency. The rated frequency for cir-

rical Current Basis Basis.. It is intended to supple supplement ment ANSI/IEEE C 3 7.0 7.0 10-1 10-1979, 979, Application Guide for AC High-Volt High-Voltage age Circuit Breakers Rated on a Symmetrical Symmetr ical Cur Curren rentt Basi Basis. s. Circuit breake breakers rs rated and manufactured to meet other standards should be ap plied in accordan ac cordan ce with application procedures adapted to their specific ratings.

breakers eakers are 4.3 Capacitance Current. Circuit br designed for application where the capacitance current, whether on an overhead line, cable, or capacitor bank, does not exceed the rated value, at any voltage, up to rated maximum voltage. For altitudes exceeding 3300 ft, (1000 m ) the capacitance current does not have to be corrected, provided it does not exceed the corrected rated continuous current.

2. Purpose Th is guide is intended for genera generall use in the application of circuit breakers for capacitance current switching. Familiarity with other American National Standards applying to circuit breakers is assumed, and provisions of those standards are indicated herein only when necessary for clarity in describing application requirements.

Generall Application A pplication Conditions 3. Genera See Section 3 of ANSI/IEEE C37.010-1979.

cuit breakers is 60 Hz. Special consideration should be given to applications other than 60 Hz. At lower frequencies, the capacitance curr ent switching ability wil willl be adequate, but ac control devices devices may n ot be suitable for th e application.

Time. T he inte rrupting time 4.4 Interrupting Time.

of a circuit breaker on capacitance current switching is the interval between the energizing of the trip circuit at rated control voltage and the interruption of the main cir-

cuit in all poles on an opening operation. Since capacitance currents are less than 25 percent of the required asymmetrical interrupti ng capability, the time required for inte rruption may be greater than the rated interrupting time. For circuit breakers equipped with resistors, the interrupting time of the resistor resis tor cu rren t may be lon longer. ger. Note als also o th at the interrupting time may be longer for close-open operations. (See 5.7 of ANSI/IEEE C37.04-1979.)

4 . Capacitance Current Switching Application Considerations

4.5 Transient

Overvoltage. An important consideration for application of circuit breakers for capacitance current switching is t h e

4.1 Maximum Voltage for Application. The operating voltage voltage should not exc exceed eed the rated

trans ient overvo overvoltage ltage which may operation. be generated by restrikes during the opening In ANSI C37.100-1972, a transient overvoltage

11

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

ANSI/IEEE

C37.012-19 9

APPLICATION GUIDE FOR CAPACITANCE CURRENT SWITCHING FOR

0 03

0 0

r-

0

3 0

In

d-

m

5

-

d-

3 1 1 w t13d

m S3t13dWtl

12

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

AC HIGH-VOLTAGE CIRCUIT BREAKERS RATED O N A SYMMETRICAL CURRENT B BASIS ASIS

ANSI/IEEE C37.012-1979

Three-conductor bundle - 0.13 MQ per phas e per mile (0.21 MJ per phas e per ki kilomelometer) Four-conductor bundle - 0.12 MQ per phase per mile (0.19 MQ per phas e per kilometer) T h e curve o off Fig 1 shows rms charging curre nt in amperes per mile' as a function of system voltage for single-conductor and two-conductor bundle lines.2 If the estimated current is greater greater than 90 percent of th e preferred line current rating, a more accurate calculation based on the actual line configuration and methods similar to th at discu discussed ssed in re referenc ference e [ 11 should be used.3 Thes e calculations assume a ttransposed ransposed line an d neglect the rise in voltage at the open end (Ferranti effect). The voltage rise has the effect of increa sing the line charging cur rent and is a function of line length. The additional current can be calculated using, for example, A B C D constants and con con--

factor is defined as the ratio of the transient voltage appearing between a circuit breaker disconnected terminal and the neutral of the disconnected disco nnected capacitance during open opening ing to the operating line-to-neutral crest voltage prior to opening. The rated transient overvoltage factor is specified specified for tw o typ es of circuit breakers: (1) General-purpose circuit breakers. The trans ient overvoltag overvoltage e factor should not exceed exceed 3.0. ( 2 ) Definite-purpose circuit breakers. The transient overvoltage factor shall not exceed the following more than once in 50 random three-phas e operations: ( a) 2.5 for circuit breakers rated 72.5 kV an d below (b) 2.0 for circuit breakers rated 121 kV and abo above ve T he selection o off th e type o off circuit bre aker to be applied should be coordinated with the insulation capability of of other components on th e system.

sidering the line open-circuited at the receiving end. The magnitude of the charging current is then

4.6 Open Wire Transmission Lines. A circuit breaker may be required require d to energize or deenergize an unloaded open wire transmission line during its normal operating duties. Prior to energization, the line may or may not contain a trapped charge. The test program of 4.13 of ANSI/IEEE C37.09-1979, Test Procedure for High-Volt%e circuit Breakers recognizes the possib possible le conditions e ncountered during the switching of op en wire lines lines.. The app lication of either gene general ral or definite-purpose circuit breakers to open wire line switching is determined by the open wire line current switching rating

where IV, I = magnitude of sending sendingend end line-to-ground voltage capacitive reac reacttX c = line positive-sequence capacitive ance per phase, in ohms X , = line positive-sequence inductive react-

assigned in ANSI C37.06-1979, Tables lA , 2A, 3A,-4A and 5A. 4.6.1 Open Wire Line Charging Switching Current. Wh When en co consider nsidering ing the assign assigned ed ope open n wire line charging switching current rating, application is determined by the value of the line charging current. This current is a function of system voltage, line length, and l ine configuration. For a first approximation of single- and double-circuit overhead line charging currents, the capacitive capacitive reactance at 60 Hz ca n be estimated as follows: Single conductor 0.18 MD per phase per mile (0.29 IVUl per phase per kilometer) Two-conductor bundle - .14 MQper phase per mile (0.23 M Q per phase per kilometer)

ance per phase, in ohms The term in brackets is a modifying factor which is applied to the current determined previously (see Fig 1) and, for a single-conductor line with 0.8 D per phase per mile inductive reactance and 0.18 MR per phase

'1 mile = 1.61 km. When using the quantity Mf2 per phase per mile, it should be remembered remembered that the sh unt cap acitive reactance in megohms for more than one mile decreases because the capacitance increases. For more than one mile of line, therefore, the value of shunt-capacitive reactanc e as given above should be divided by the number of miles of line. 3Anexample 3An example of thi s calculatio n is given in Appendix Appendix A .

13

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

ANSI/IEEE C37.012-1979

APPLICATION GUIDE FOR CAPACITANCE CURRENT SWITCHING FOR

per mile capacitive reactance, the current magnitude is approximately approximately .8 (100s)

3 = IIc’I

where II,’I

=

0 . 1 8 X 106/(100S)

[1 + O . O 1 4 8 S 2 ]

uncorrected current

S = line length, in hundreds of miles

The corresponding equation for a two-conductor bundle with 0.6 Q per phase per mile inductive reactance and 0.14 M Q per phase per mile capacitive reactance is

II,I = II,’l

[l + O.O143S2]

Examination of these equations indicates indicates an error of approximately 1.5 percent at 100 mi. T h e Fe rran ti effect effect can be neglect neglected ed for lines lines lesss than this length. les 4.6.2 Compensated Open Wire Transmission Line Current. Extremely long lines are often

compensated with shu nt reactors to reduce the amount of charging current required of the system. syste m. The compensation factor F , is defined as F =- C (Eq 1) xR

where X , = inductive reactance of compensat ing reactor

line could not be switched without the compensating reactor(s) connected. The voltage rise caused caused by the Fer ran ti effect effect and also the location of of t he reactor(s) will will change th e line curren t slightly. 4.6.3 Line Charging Transient Recovery charging switching Voltage. The open wire line charging current is assigned the basis of a standardrating transient recovery on voltage associated with this typ e of ci rcuit. The tests discussed discussed in 4.13 of ANSI/IEEE C37.09-1979, which demonstrate performance, are based on the test voltages of 4.13.4 of ANSI/IEEE C37.09-1979. The open wire line charging current switching tests require a maximum voltage of 2.4 times rated maximum phase-to-ground voltage across the circuit breaker one half-cycle after interruption (assumes C1 = 2 C O here C I is the positive-sequence capacitance and C O s the zero-seq zero -sequenc uence e capacitance). T hi s is th e difference voltage of the source and line sides, inclu ding th e effects of coupled voltage voltage on th e first phase to clear. clear. T h e test voltage voltage requires requires a 1- cosine waveshape. Deviations from the te st voltage voltage characteristics may increase or decrease decrease the probability probability of the circuit breaker restriking. For example, if t he line is compensate d, the li ne side component is not a trapped voltage but is an oscillation with a frequency determined by the compensating reactors and the line capacitance. T he resonant frequency of the compensated line is approximated by

Th e factor factor F , times 100 is the “percent compensation.” If X R is great greater er th an X c the line is undercompensated, if X R is less thancomX c the line is overcompensated. The pensated line charging current is then given by 11, = I c ’ (1 F c )

where fL =

line resonant frequency, in hertz

L = reactor inductance, in henrys in farads C = to ta l capacitance of line, in f , = system frequency, in hertz

(Eq 2)

where

11, = compensa ted line charging charging current I,’ = uncompensated line current (see Section 4.6.1) F , = compensation factor (Eq 1

A simple substitution indicates

Assuming a line compensated a t 60 percent, the line charging current is 11,= I,’ (1

Since F, th e compensation fact or, is is usually usually

.6) = 0.41,’

less than 1, the line resonant frequency is correspo corr espondin ndingly gly less th an th e system frequen-

or 40 percent of the uncompensated value. If th e breaker ratin g is chosen chosen based on I l , , the

CY.

14

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

AC HIGH-VOLTAGE CIRCUlT BREAKERS RATED ON A SYMMETRIC SYMMETRICAL AL CURRENT BASIS

In

ANSI/IEEE

(237.012-1979

/

Fig 2 Typical Current and Voltage Relations for a Compensated Line Typical current and voltage relations are

clear, resulting in increased probability of

given in Fig 2.  2.   T h e first half-cyc le o off recovery voltage is, for 3.  Compenthis example, as shown in Fig 3.  sation thus reduces the probability of restriking at a particular current. Under these conditions improved performance may result, th e breaker becoming restrike-f restrike-free ree or possibly able to interrupt higher values of charging current. The manufacturer should be consulted on applications which markedly alter the transi ent recovery recovery voltage. voltage. If the C d C o ratio is greater than 2, higher voltages may be coupled to the first phase to

restrikes. this case since the circuit manufacturer should also In be consulted breaker designs are sensitive to both current magnitude, an d recovery voltage waveshapes. waveshapes. 4.7 Capacitor

Banks. A circuit breaker may

be required to switch a capacitor bank from a bus that does not have other capacitor banks energize ener gized d (isolated) or against a bus that has other capacitor banks energized (back to back). In the application of circuit breakers for capacitor switching duty, consideration must be given to the rated isolated shunt capacitor bank sw itching current, rated back-

Fig 3 First Half-Cycle of Recovery Voltage

I

/

/

w 3

a

/

c

/

/-

UNCOMPENSATED

/

J

/

I

IL

w

a

0

0

0.25

0.5

CYCLES

15

Authorized licensed licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

ANSI/IEEE

C37.012-1979

APPLICATION GUIDE F O R CAPACITANCE CURRENT SWITCHING FOR

to-back shunt capacitor bank switching current, rated transient inrush current, and rated transient inrush current frequency. frequency. 4.7.1 Capacitor

equal to

-

maximum voltage voltage

Bank Current. Circuit

breakers are to be applied according to the actual capacitance current they are required to inte rrupt. Th e rating should be be selecte selected d to include the following following effects effects.. reactive ve (1) Voltage Factor. Th e nameplate reacti power rating of the capacitor bank, in kilovars, is to be multiplied by the ratio of the maximum service voltage to the capacitor bank nameplate voltage voltage when calculating the capacitance current at the applied voltage. Th is factor can be as large as 1.1, since capacitors can be operated continuously up to 10 percent above th e capacitor r ated voltage, ( 2 ) Capacitor Tolerance. Th e m an u facturing tolerance in capacitance is - 0 to +15 percent with a more frequent average of of - 0 to + 5 percent. A multiplier in th e range of

where I=rated rms short-circuit current, in amperes w = 27rf = 377 or 60 Hz system The ratio [(rated maximum voltage)/(operati ng voltage)] shall not exceed exceed th e voltage voltage range factor K as given in ANSI C37.06-1979, Tables 1  hrough 5. 4.7.3 Back-to-Back Capacitor Bank. T h e inrush current of a single bank will be increased when other capacitor banks are connected to the same bus. As defined in 13.3 of ANSI/IEEE C37.04-1979, capacitor bank is considered switched back to back if the highest

1.05 to 1.15 should be used to adjust the nominal curr ent to t he value allowed by tolerance in capacitance. capacitance. (3) Harmonic Component. Capacitor banks provide a low-impedance path for the flow of harmonic currents. When capacitor banks are ungrounded, no path is provided for zerosequence sequ ence harmonics harmonics (third , sixth, ninth , etc), and the multiplier for harmonic currents is less. A multiplier of 1.1 s generally used for a grounded neutral bank and 1.05 for an ungrounded neutral. In the absence of specific information on multipliers for the above factors, it will usually be conservative to use a tota l m ultiplier of 1.25 times the nominal capacitor current at rated capacitor voltage for ungrounded neutral operation and 1.35 times the nominal curre nt for grounded grounded neutral operation. operation. 4.7.2 Isolated Capacitor Bank.

A bank of

shunt capacitors is considered isolated when the inrush current on energization is limited by the inductance of the source and the capacitance of the bank being energized. As defined in 5.13.2 of ANSI/IEEE C37.04-1979, a capacitor bank is also considered isolated if the maximum rate of change, with respect to time, of transient inrush current on energizing an uncharged capacitor bank does not exceed the maximum rate of chan change ge of th e symmetrical interrupting cu rrent at the voltage voltage at which which the circuit breaker is applied. The limiting value is

16

rate of change of inrush current on closing closing exceeds that specified for isolated capacitor banks of 5.13.2 of ANSI/IEEE C37.04-1979. energization ion of a 4.7.4 Inrush Current. Th e energizat capa citor ban k by the closing of a circuit breaker will result in a transient inrush current. The magnitude and frequency of this inrush current is a function of the following: applied voltage voltage (poin t on th e voltage voltage wave wave a t closing) , capacitance of the c ircuit, inductance in t he circuit (amount and location), any charge on the capacitor bank at the instant of closing, and any damping of the circuit due to closing resistors or or other resistance in t he circuit. circuit. The transient inrush current to a single (isolated) bank is less th an the available shortcircuit current at the capacitor bank terminals. Since a circuit breaker must meet the momentary current requirements of the system, transient inrush c urrent is not a limiting limiting factor in isolated isolated c apacitor bank applications. applications. When capacitor banks are switched back to back, th at is, when when one ba nk is switched while another bank is connected to the same bus, transi ent curre nts of of prospective prospective high high magnitude and with a high natural frequency may flow between the banks on closing of the switching device or in the event of a restrike on opening. Th is oscillatory curre nt is limited limited only by the impedance of the capacitor bank an d th e circuit between the energized energized bank or

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

AC HIGH-VOLTAGE CIRCUIT CIRCUIT BREAKERS RATED O N A SYMMETRICAL CURRENT BASIS

ANSI/IEEE C37.012-1979

Table 1 Inrush Current and Frequency for Switching Capacitor Banks Condition

Qua ntit y

Energizing Energ izing an isolated ba nk

i f

pk

(amperes)

When Using Using Currents 1.414-

(hertz)

Energizing a bank with another on the same bus f (kilohertz)

Energizing a bank with an eq ual Energizing bank energized energized o n th e same bus

f

= System frequency

banks,, in microhenrys Leq = Total equivalent induct ance per phase between c apacito r banks

I 1 , 1 2 = Currents of bank being switched and of bank already energized, respectively. Capacitor bank being

switched is ass assumed umed uncharged, w ith closi closing ng at a voltage voltage crest o off the sourc e voltag voltage. e. The current used should include t he e ffect of ope rating th e capacitor bank at a volt voltage age a above bove nominal nominal rating rating of the capacitors and the effect of a positive tolerance of capacitance. In the absence of specific informat ion, a multiplier of 1.1 times nominal capacitor current would give conservative results imaxpk = A peak value calculated without damping. In practical circuits it will be about 90 percent of this value VLL = Rated maximum voltage in kilovolts I = Symmetric Symmetrical al rms short-c ircuit current, in amperes.

banks and the switched switched bank. This transient current usually decays to zero in a fraction of a cycle of of t he sys tem frequency. I n t he case of of back-to-back switching, the component supplied by by th e source is at a lower lower frequency frequency and

where

C = farads L = henrys I = amperes f = hertz

small itMethod may be neglected. so4.7.4.1 f or Calculatin Calculating g Trans ient Inrush Currents.  Currents.  Table 1  gives g ives the formula for calculating inrush current and frequency for both isolated isolated an d back-to-back back-to-back capacitor bank switching, neglecting resistance. These formulas are based on th e followin following g fundam ental relationships : .=-

E

m

sin

A typical circuit for back-to-back switching is

shown in Fig 4. Th e inductance inductance in the circuit circuit that limits the transient oscillatory current is composed of of th e indu cta nce of th e bus between swit ching devices, L bus, the inductance inductance between betw een t he switching devic device e and the capacitor banks, L I and L2, and the inductance of th e capacitor capacitor banks, L c i and Lc2 . The total inductance between capacitor banks, L c i + L I + L bus + Lz f Lc2 , is very small with respect resp ect to t he in ductan ce of of th e source L s . I n most cases, the total inductance between capacitor banks will be less than one percent of

t / a )

1 =

the inductance of of th e source, and t he contribution of transient current from the source can be neglected.

n 4 m

See Appendix B.

17

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

ANSI/IEEE C37.012-1979

APPLICATION APPLIC ATION GUIDE F O R CAPACITANCE CURRENT SWITCHING FOR

SOURCE

SWI

L bus

sw2

L2

c2

L c2

------9i--/--I---

Fig 4 Typical Circuit for Back-to-Back Switching SWll Circuit Br SW Breaker eaker Energizing Capacitor Ba Bank nk 1 SW, Cir Circuit cuit Breaker(s) Breaker(s) Connecting Connecting Another Bank(s) t o Bus Ls Source Inductance L c 1 , L 2 Capac Capacitor itor Bank Induct ance L1, L2 Bus Inductance Between Switching Device and Capacitor Bank Lbus Inductance of Bus Between Switching Devices

18

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

AC HIGH-VOL HIGH-VOLTAGE TAGE CIRCUIT BREAK ERS RATED ON A SYMMETRICAL SYMMETRICAL CURRE NT BASI BASIS S

T he inductance of t he bus can be calculated similar to a transmission line using values of (for one-foot spacing) and x d (spacing fac tor ) from tables available from suppliers of bus conductors for different bus configurations. (See 4.7.4.2.) T he inductance within within t he capac capacitor itor bank its itself elf is not easy to obtain, but i n general general i t is of the order of 10 pH for banks above 46 kV, a n d 5 P H or banks below 46 kV. Typical values of of induc tance per phase between backto-back capacitor banks an d bank inductance for various various voltage lev levels els are given in Ta ble 2. Inherent resistance of the circuit causes rapid decay of the transient current so that th e first pea peak k actually m ay only reach reach 90 to 95 percent of the maximum value calculated. These values are applicable to both grounded or ungrounded banks and with wye or delta connections. With an ungrounded neutral, th e current in t he first two phases t o clos close e wil willl

x,

be 87 percent of calc calculat ulated, ed, but t he curr ent in t h e last phase will equal the value calculated. However, inherent resistance of the circuit will affect these currents by the factors indicated above above.. The formula in Table 1  for back-to-back switching will give correct results when switching a bank against anothe r bank. However, when switching against several other banks conn connecte ected d to t he bus, th e corre correct ct value of equivalent inductance to be used for the combination of banks connected to the bus is not easily obtained. For example, when switching a bank against three other banks energized on the bus, the calculated current will be too high if a n in duc tan ce o off L/3 is used. On the other hand, using a value of 3L will result in a current which is too low. If exact solutions cann ot be made, conservative conservative results should be be use used d in calculatin calculating g inru sh currents by using using th e inductance divided divided b by y t he number of capacitor banks, recognizing that the results will be from 20 t o 30 percent too high. 4.7.4.2 Considerations for Transient Inrush Currents. T h e inrus h curr ents o off dif differ fer--

ent types of compact multisection banks with minimum spacing between the individual sections may differ by as much as 20 percent. Consequently, these inrush currents c an be reduced significantly by increasing the lengths (inductance) of the circuits between th e secti sections. ons.

ANSI/IEEE C37. 012- 1979

Table 2 Qp ic al Value Valuess of Inductance Between Capacitor Banks Rated Maximum Inducta nce per Voltage Phase of Bus (kV) (PH/ft) 15 3 8 .5 and below 48. 3 72.5 121 14 5 169 242

0.214 0.238 0.25 6 0.25 6 0.26 1 0.26 1 0.26 8 0.285

Typic9 Typic91 1 Inductan ce Between Banks* (PH) 10-20 10-20 15-30 20-4 20-40 0 25-5 25-50 0 3 5-7 0 40-8 40-80 0 60-1 60-1 20 85-170

*Typic al values of inducta nce per phase between capacitor banks. banks. This does no t include inductance of the ca pacitor bank itself. Values of 5 pH fo r banks bel below ow 46 kV and 1 0 pH for banks above 46 kV are typicall for th e inductance of the capacitor banks. typica

Another effective measure to reduce transient inru sh current currentss is to add inductanc inductance e in th e circuit be betwe tween en t he capacitor banks. The magnetic fields associated with high inrush currents during back-to-back switching in either the open wire transmission line conductors or the grounding grid during backto-back switching can induce voltages in control cables by both capacitive and electromagnetic coupling. These induced voltages can be minimized by shielding th e cables and using a radial configuration for circuits (circuits complet completely ely contained within one cable so that inductive loopss ar e not formed). loop The high-frequency transient inrush current associated with back-to-back switching can stress other equipment in the circuit as well as the circuit breaker. Wound-type current transformers will have turn-to-turn insulation stressed because of the high rates of rise of of current an d th e resulting resulting voltag voltage e th at is developed across inductance in the circuit. The following example will illustrate the use of of th e formulas in  Table 1.  1.   A 115 kV system is assumed as shown in Fig 5. Capacitor banks shown have a nominal rat in g of 12 Mvar (capacitors rated 100 kvar, 13 280 V, five five series series sections with eight capa citors in parallel). Nominal cur rent per bank is 60 A. In determining the rating of the circuit breaker required, the increase in current due to appl applied ied voltag voltage, e, ca pacitance tolerance, an d harmo nics should be considered. T h e iincrease ncrease

19

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

ANSI/IEEE

1979 79 C37.0 1 2  19

APPLICATION GUIDE FOR CAPACITANCE CURRENT SWITCHIN SWITCHING G FOR

I

B A N K 3  12 M v a r

tl

B A N K 2  12 M v a r

c-c

BANK I 12 Mvar

Fig 5   Example of 115 kV System V,,

max

1 2 1 k V (115 kV nominal voltage)

Ls,Source Inductance, = 3.77a2, 0  mH mH L1 , 2 , L3 hductance Between Circuit Breaker and Capacitor Bank, Including Inductance of Capacitor Bank L b u s Inductance of Bus Between Switching Devices Short Circuit of Source 1 8  600 A at 1 2 1 kV

voltage is: maxa t maximum rated voltage imum voltage to capacitor rated voltage = 1211115 = 1.05. Assume a positive tolerance of capacitors of +10 percent, multiplier of 1.1, an d assume a multiplier multiplier for harmonic harmonic c ontent for a grounded neu tra l bank of 1.1. in current

The total multiplier used to determine the isolated and back-to-back current rating is 1.05 x 1.1 x 1.1 = 1.27, giving a cur ren t of 1.27

76 A. With capacitor banks 2  and 3   energized, energ ized, the curre nt through PCBz is 152 A. x 60

=

Definite-purpose circuit breakers meeting meeting th e above requirements should be selected from the appropriate table in ANSI C37.06-1979. For illustration, the following ratings ratings are assumassumed: rated maximum voltage 121 kV, rated continuous current 1600 A, rated short-circuit current 40 kA, rated isolated and back-to-back capacitance switchin switching g current 1 60 A.

20

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

AC HIGH-VOLTAGE HIGH-VOLTAGE CIRCUIT BREAKERS RA TED ON A SYMMETRICAL CURR ENT BASIS

Th e transi ent inr ush current an d freque frequency ncy 1.  are calculated calculated using using t he formulas in Table 1.  In the example, L1: Lz,' and L3'a re th e inductances between the respective capacitor banks a nd t he circuit circuit breakers, breakers, including including the inductance of the capacitor capacitor bank. L bus is the inductance of the bus between the circuit breakers. The inductance values in Table 2 can be used or values values can be calculated for th e actu al bus configuration used. In the example, the bus is is an extruded aluminum tube with an 8 f t (2.4 m) phase spacing. The section between breakers is 3 in (76 mm) iron pipe size (IPS) and between breaker and capacitor it is 2 in (51 mm) IPS. F o r 3 i n ( 7 6 m m ) IPS, X , = 45.2 p Q / f t [ a t 1 t (304.8 mm ) spacing] and f o r 2 in (51 m m ) IPS, X, = 54.2 p n / f t [at 1 f t ( 3 0 4 . 8 m m )

spacing]. x d f o r 8 f t (2.4m) phase spacing = 5 3 p n / f t n) = X, X, (2 ( 3in) = Xa X,

45.2 53.0 = 98.2 X, ==54.2 53.0 = 1 0 7 . 2ppRn // ff tt L ( 3 n) = 0.261 p H / f t L ( 2 i n ) = 0.285 p H / f t x d

Th e distance between circuit breakers is 144 f t (43.9 m ) of 3 in bus. Th e distance between between bank 1 and PCBl is 35 f t (10.6 m). The distance between between ban k 2 and PCBz and bank 3 and PCB, is 60 f t (35 + 25) (18.3 m ) of 2 in bus. Assume inductance of capacitor banks of 10 PH. The following inductance values are used in th e example: L b u s = ( 1 4 4 ) ( 0 . 2 6 1 ) = 37.6 P H (35) (0.285) + 1 0 p H = 20.0 p H L1

L p f L a f= ( 6 0 ) ( 0 . 2 8 5 )

10 p H

=

27.1 p H

k a x pk

ANSI/IEEE C37.012-1979

1.4 d E ( 1 . 4 ) d 1 8 600 X 69 ( 1 . 4 ) 4 1 2 8 X 104 = ( 1 4 0 ) (11.3)= 1 5 8 2 A peak

= =

=

6 0 &9=

9 8 5 Hz

T h e calculated ra te of of change of of curre nt for th e single-bank switching is

This is less than the maximum rate of change for a rated short-circuit current of 40 kA which is equal to 27r f a 1 (377) (1.4 ) (40) = 21.3 A/ps and therefore meets the requirements of isolated capacitor bank switching. Case I I . Energization of bank 1 with bank 2 energized on the bus (back-to-back switching against an equal-si equal-size ze bank),

The equivalent inductance L e , is the sum of

= 12 250

A peak

= ( 1 3 . 5 ) (1.11) 1 5 . 0 k H z

In determining inrush curren t and frequency, the currents I I and IZ s used in Table 1   should include th e effect effect of of opera ting the capacitor bank at a voltage above nominal rat ing of the cap acitor s and the effect effect of a positive tolerance of of capac itanc e. In th e exexample, the multiplier to be used is [(1.05) (1.1)] = 1.15. Th e currents are I I = (60) (1.15) = 6 9 A and I2 = 6 9 A or 138 A, depending on whether bank 2 or 3 or both banks are energized.

The calculated back-to-back inrush current and frequency must be compared with the back-to-back switching capability listed in the appropriate tables of A N S I C37.06-1979. or a maximum voltage of 121 kV, the assumed rated values are 1 0 kA and 5.3 kHz. The calculated valuess of inrush curre nt and freque value f requency ncy of 12.25 kA and 15.0 kHz exceed those assumed and inductanc e must be added between between th e capacitor banks to reduce the inrush current and frequency. Adding an inductance of 0.6 m H willl limit the inr ush current t o approximately wil

Case I. Energization of capacitor bank 1 with banks 2 and 3 not energized (isolated switching),

5 kA and the frequency to approximately 5.0 kHz, both of which are below the assumed capability.

-

21

Authorized licensed licensed use limited to: University of Massachusetts Boston. Downlo Downloaded aded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

ANSI/IEEE

C3 7.012 12-1 -19 99

APPLICATION GUIDE FO R CAPACITANCE CURRENT SWITCHING SWITCHING FOR

Case 111 Energization of bank 1 with banks

2 and 3 energized on the bus. For this case, assume the equivalent inductance of banks 2 and 3 equal t o one half of Li or (27.1)/2 13.6 rH. T h e total curr ent of of banks 2 and 3 is 138

A, which is under the assumed isolated bank switching capability of 160 A as listed in

ANSI C37.06-1979. For this case, Il = 6 9 A, I2 = 138 A , and the equivalent inductance

between the capacitor bank being energized and the banks already energized is the sum of L i / 2 + Lbus + L i = 13.6 + 37.6 + 20 = 71.2

P

H.

more cables energized (back to back). In the application of circuit breakers for cable switching duty, consideration must be given to the rated isolated cable switching current, the rated back-to-back cable switching current, and the rated transient inrush current, both amplitude and frequency. frequency.

4.8.1 Isolated Cable. A cable is defined as isolated if the m aximum ra te of of change, with respect resp ect to time, of of transient inrush c urren t on energizing a n unchar ged cable doe doess not exceed exceed the rate of change of current associated with the maximum symmetrical interrupting current (see 4.4). This limiting value is numerica numerically lly equal to maximum

= =

9.5

1747

1 5 500 A peak

W =

J7m-mmw

=

9*5

( 71.2) ( 69) (138)

=

(9.5) (1.49) = 14.1 kHz

9.5

T he calculated values of inrush c urrent a nd frequ ency of 15.5 kA and 14.1 kHz exceed the assumed back-to-back switching capability of 1 0 k A and 5.3 kHz listed in ANSI C37.06-1979. As in the previous case of switching identical banks, adding an inductance of 0.6 mH will limit the inrush inrush current and frequency to within the assumed back-to-back switching capability of 121 kV circuit breaker. Based on the system and conditions studied, a circuit breaker having the following ratings would be applied: rated short-circuit current of 40 kA and rated isolated capacitor 160A. bank switching current of 160 A. Th e assumed assumed back-to-back r at ing of 10 kA and 5300 Hz t h at goes with this rating will be exceeded unless additional inductance is added between the capacitor banks. A value of 0.6 mH is suf-

ficient to keep within the assumed ratings available. 4.8 Cables. A circuit breaker may be required to energize or deenergize an unloaded cable during its normal operating duties. Prior to energization the cable is usually at ground poten tial. A cable may be switched from a bus that does not have other cables energized (isolated) or against a bus th at has one or

where I = rated rms short-circuit current, in amperes w =

=

377 for 60 H z system The ratio [(rated [(ra ted maximum voltage)/(operating voltage)/(ope rating voltage)] shall not exceed the voltage range factor K. definition it is possible possible to have cable By this definition circu its which which are physically back to back, but are considered isolated for application purposes provided a large inductance is located between the two cable circuits. The inductance must be large enough so that by itself it would limit fault current to a value less th an or equal to the circuit breaker breaker rating. 4.8.2 Back-to-Back Cables. Cables are considered switched back to back if if th e maximum rate of change of transient inrush current on energizing an uncharged cable exceeds that specified fo r an isolated cable (see 4.5). 4.8.3 Cable Charging Current. The cable charging current is a function of system voltage, cable geometry, insulation dielectric consta nt, a nd cable cable length. length. T he sh unt capacit capacitive ive reactance can be obtained from the manu2 nf

facturer, or if the physical constants of the

cable are known, the shunt capacitive reactance can be calculated [3]. For single-conductor and three-conductor shielded cables the sh un t capacitive capacitive reactance can be be written I=-

4.12

log,,

fsk 5

S e e Footnote 2

2 ri

d

M a per phase per mile5)

22

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE IEEE Xplore. Restrictions apply.  

AC HIGH-VOLTAGE CIRCUIT BREAKERS RATED ON A SYMMETRICAL CURRENT BASIS

where f , = system frequency, in hertz k = dielectric constant of cable dielectric material r i = inside radius of shea sheath, th, in fee t d = outside diameter of of conductor, in feet Using the capacitive reactance, the cable charging current can be calculated and compared with th e rated cable charging curre nt of of th e circuit breaker. Befo Before re an application can be made, the i nrush c urrent rat ing should als also o be checked. 4.8.4 Cable Inrush Current. The energization of a cable by th e closing of a c ircui t breaker will result in a transient inrush current. The magnitude and rate of change of thi s inrus h curre nt is a function o off th e follow follow-ing: applied voltage (including the point on the voltage wave at closing), cable surge impedance, cable capacitive reactance, inductance in the (amount andinstant location location), any charges oncircuit the cable at the of), closing, and any damping of the circuit because of of closing resistors or other res istance in the circuit. The transient inrush current to a single (isolated) cable is less than the available short-circuit current at the circuit breaker terminals. Since a circuit breaker must meet the momentary current requirements of the system, trans ient i nrush cu rrent is not a limiting factor in isolated cable applications. When cables are switch switched ed bac back k to back (t ha t is, when one cable is switched while other cables are connected to the same bus), transient current s o off high magnitude and ini tial high rate of change may flow between cables when th e switching circuit break er is close closed d or restrikes on opening. This surge current is limited by the cable surge impedances and any inductance connected between the energized cable(s) and the switched cable. This transient current usually decays to zero in a fra cti on o off a cycle of th e syste m frequency. During back-to-back cable switching, the component of of cu rre nt supplied by the source is lowe werr rate of change an d so small tha t it at a lo may be neglected. 4.8.4.1

Method for Calculating Transient

Inrush Currents. A typical ci rcuit for back-to-

ANSI/IEEE C37.012-1979

back cable switching is shown in Fig 6.  6.  T h e inductances Li, L z , and Lbus between the cables are often very very small with respect to the inductance L , of th e source. I n many cases they will be less than 1 percent of the source inductance. They consist of the inductances from the cables to the circuit breakers, the circuit breaker inductances, and the bus inductance of the current path. Values of inductance depend upon the physical configuration. A representative range is 0.2 to 0.3 p H er phase per foot. In switching an isol isolated ated cable, if the source source inductance is greater than 10 times the cable cable inductance, the cable can be represented as a capacitor (see 4.7). Otherwise, under transient conditions the cable can be represented by its surge impedance. An expression ex pression for fo r surge impedance [3] is given for single-conductor and t hree-conductor shielded shielded cables by

where L = distributed inductance of cable, in henrys ribut ed capa capacitance citance of of cable, ca ble, in C = dist ributed farads h = dielectric constant of cable dielectric material r 2 = inside radius of of sheat s heath, h, in feet r l = outside radius of conducto r, in feet Average values for k are between 2.5 and 4; a n average value for 2 is 50 9 4.8.4.1.1

Back-to-Back Cable Inrush

Neglectin cting g t he source source contribution, Current. Negle back-to-back cables can be represented as shown in Fig 7.  7.  The initial pulse of current has a front expressed as

Assuming Assumi ng tha t th e L / Z 1 + 2 2 ) time constant is less than of the travel time of the cable out a nd back, the initial crest of of the inrush current is then E m - E t ) / Z i + Z2 , which for application should be less than the rated peak inrush current.

23

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

ANSI/IEEE

C37.012-1979

APPLICATION GUIDE FOR CAPACITANCE CURRENT SWITCHING FOR

PCB 2

Fig 6 Typical Circuit for Back-toBack Switching PCBll Open for I solated Cable Switching, Close PCB Closed d for Back-to-Bac k Switching PCB2 Switching Device Ls Source Inductance L1, Lz Inductance Between Cables 1 nd 2 and Bus Z1,22 Surge Impedance of Cables 1 and 2 C1, C2 Capacitance of Cables 1 and 2 Lbus Inductance of Bus Connecting the Cables

Fig 7 Equivalent Circuit for Back-to-Back Cable Switching E

Crest of Applied Voltage E , Trapped Voltag Voltage e o n Cable Be Being ing Switch Switched ed Z1, Z2 Cable Surge Impedance L Total Circuit Inductance Between Cable Terminals

24

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

AC HIGH-VOLTAGE CIRCUIT CIRCUIT BREAKERS RATED ON A SYMMETRIC SYMMETRICAL AL CURRENT BASIS

ANSI/IEEE C37.012-1979

Table 3 keq uen cy and Current Amplitu Amplitude de Relations Relations Condition

Quantity

When Using Surge Impedance

Energizing Energiz ing an isolated cable

Energizing Energizi ng a cable with another on the same bus

Energizing a cable with an equal Energizing cable energized on the same bus

Differentiating the expression expression for curren t at t = 0 , the maximum initial rate of change of the inrush curr ent is

Thi s can reach extreme values values since since the magnit ude of L can be arbitrarily small. The cable inrush current is not oscillatory in the usual frequency-related sense, but the initial slope can be used to determine an equivalent frequency which can be compared with the rated inrush frequency. In general,

where (dildt), = ra te of of change change of rated inrush current f R = rated inrush current frequency I M R rated peak inrush current (see

Em -Et

22

an d for proper proper breaker ap plication, feq should be less less tha n th e rated inr ush current frequency. Additional inductance may be added in series with the inductances making up L to meet the rate d inr ush frequency requirement. Frequency and current amplitude relations are summarized in Table 3.  4.8.4.1.2 Alternate Configurations. Other combinations of circuit elements can produce inrush currents associated with cable switching. For example, a cable can be switched from a bus which has a capacitor bank connected as shown in Fig 8. 8.   The inrush curr ent c an be calculated using using the equivalent circuit of Fig 9. T h e maximum in itial rate of change of curr ent is given given by by t he expression expression

ANSI C37.06-1979)

The equivalent frequency for a cable inrush current is then

and, as before, is limited by the loop inductance L. The equivalent frequency is determined as in 4.7.4.1, nd required adjustments can be made by increasing the value of L (reacto r, iron pipe, etc).

25

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

ANSI/IEEE

APPLICATION GUIDE F O R CAPACITANCE CURRENT SWITCHING FOR

C37.012-1979

PCBi

SYSTEM

TC Fig 8 Bank-to-Cable Switching Circuit PCBl Switchi ng Device L s Source Inductance L Total Inductance Between Bank and Cable 2 Cable Surge Surge Impe dance C Capacitance of Bank

/

Equivalent Bank-to-Ca Bank-to-Cable ble S w i t c h i n g Circuit E,

Crest of Applied Voltage

Et Trapped Voltage on Cable Being Switched

2 Cable Surge Impedance L Circuit Inductance Between Bank and Cable C Capacitance of Bank

26

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

AC HIGH-VOLTAGE CIRCUIT BREAKERS RATED O N A SYMMETRICAL CURRENT BASIS

T h e fo form rm of of th e inrush c urrent is a function of th e circuit parameters which, in th e equivalent circuit, form a series RLC circuit. Using standard methods of analysis, the maximum peak pea k inru sh currents are

where

ANSI/IEEE

C37.012-1979

ing the same number of amperes di directly. rectly. T he capacitive elem ents of of th e circuit will oscillate with the transformer inductance, which may also saturate , producing a less severe severe trans ient recovery voltage and a lower probability of restriking. If a restrike should occur, the additional ind uctance wi will ll help to limit limit the inru sh current. greater than 1, switching If th e value of N is greater through a transformer will have the effect of increasing the current being switched. Dropping EHV and UHV lines with lower voltage circuit breakers can result in effective line charging currents in the 750-1000 A range. The capacitance switching rating of circuit breaker s which may be ex expose posed d to th is type of duty must be carefully checked before application is made. Voltage and current relations are shown in Fig 10 as an example of capacitor switching through a n interposed transformer. 4.10 Unusual Circuits. In the application of

breakers may be required in some applications to switch capacitors, lines, or cable cabless through an interpo interposed sed transformer. transformer. T he current switched by the ci rcui t breaker will be N times the capacitor, line, or cable current on the other side of the transformer, where N is the

circuit breakers in stations having banks of capacitors it may be necessary to investigate the effects effects of trans ient currents and other special situations upon circuit breakers other than those specially equipped for and assigned signe d to the routine capacitor switching. T h e trans ient c urre nts o off capacitor capacitor banks may be considered in two aspects: the inrush curre nts upon energiz energizing ing of th e banks an d the discharge currents into faults. Where the quantity of parallel capacitor banks installed in a station is large, the transient currents may have significant effects upon the breake breaker. r. The transient currents may have large peaks and high frequency which may affect circ uit breakers in t he following ways. (1) A circuit breaker may be subjected to a transient inrush current which exceeds its rating. Th is may occur with th e circuit breaker in the closed position or when closing into bolted-type faults. ( 2 ) The transient inrush current may have sufficient magnitude and rate of change to flash over the secondaries of linea r couplers or bushing current transformers, or the associated control wiring. There are also special situations that m a y

transformer turns ratio. Switching charging current through a transformer may be les lesss di difficult fficult th an switch-

arise in fault switching sequences where circuit breakers in a stati on may get involved involved in unplanned clearing of energized parallel

For application, the peak inrush current should be be checked against t he rated value for for the circuit breaker in question. Many other combinations of banks, cables, an d lines wi will ll occur in practice. Fo r example, a cable may be used to exit from a substation and then connect to an open wire transmission line after a short distance. One possible approach when considering circuits of this type is to compare the relative contributions of the cable and the line. For short cable runs this circuit could be considered the equivalent of a line with a capacitor to ground replacing the cable. Similar simplifications can be used for other configurations. 4.9 Switchin g Thr Through ough Transformers. Circuit

27

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

ANSI/IEEE C37.012-1979

APPLICATION GUIDE

FOR CAPACITANCE CURRENT SWITCHING FOR

TRANSFORMER SATURATES \

C A P A C IT0 R B A N K CURRENT

\

W

CAPACITOR B AN K VOLTA VOLTAGE GE

Fig 10 Voltage Volt age and Current Relations for Capacitor Switching Through nterposed Transformer banks. This section is intended to guide the engineer engin eer to ta ke either t he required correc corrective tive measures or to avoid the problems. 4.10.1 Exposure t o Transient Inrush Currents. Circuit breakers located in a position such as a tie circuit breaker between bus sections may be exposed to the transient inrush currents from energ energizing izing bank s o off capacitors when they are located on bus sections sections on 11, , P C B l )the both sides o f th ethe breaker (see  (see  Fig 11 . Seldom will inrush current exceed closing- latc hing capability of t he breaker.

However, a check may be required to determine t ha t the rate o off change of of inru sh current will not cause secondary flashover of linear couplers or of bushing current transformers located locat ed o n th e circuit breaker. With linear coupl couplers, ers, the secon dary v voltag oltage e induced across the terminals from the transient capacitance current is proportional to the frequency and to the amplitude of this curre nt as shown in t he follo followin wing g formul formula: a: inear coupler

(lin (linear ear

(transie nt frequ ency)

= coupler secondary er ratio) X frequency) (system (crest)volts coupl (crest X transi transient ent current)

Th e followin following g example wi will ll illustrate th e use of the abov above e formula. Linear coupler ratio - V per 1000 primary amperes Frequency of of transie nt inrush current - 400 Hz Crest of transient inrush current - 0 000 A System frequency - 0 Hz linear coup1er secondary volts = (crest)

400

Oo0

6o

x

30 000

=

1 3 500 V

Manufacturer's voltage limits for linear couplers should no t be exceed exceeded. ed. With a bushing-type current transformer (BCT), he volta voltage ge dev develo eloped ped in t he secondary secondary circuit is also proportional to the frequency and the amplitude of the transient inrush curre nt, as shown in t he follo followin wing g formula: formula: voltag voltage e in

BCT secondary =

(crest)

1

(BCT (BC T ratio)

(crest transient current)

(transient (relay fr'equency fr'equency x reactance) x (system frequ2ncy)

28

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

AC HIGH-VOLTAGE HIGH-VOLTAGE CIRCU CIRCUIT IT BREAKERS RATED ON A SYMME SYMMETRICA TRICAL L CURRENT BASIS

ANSI/IEEE C37.012-1979

PCB

1

I

I

Fig 11 Sta tio n Illu Illustrating strating Larg Large e Transient Inrush Currents Through Circuit Breakers from Parallel Capacitor Banks The follo following wing example w will ill illustr illustrate ate th e use of th e above formula. Bushing current transformer ratio = 1000/5 Frequency of transient transient inrush curre nt = 5400 H z Crest Cre st of transient inrush current = 30 000 A Relay Rel ay reactanc reactance e burden a t 60 H z = 0.3a System frequency = 60 Hz voltage in BCT - 5 secondary (crest) 1000 =

4050 V

30 Oo0

0-3

5400 0

The secondary voltage voltage should not exceed those values specified in ANSI C57.1 C57.13-197 3-1979, 9, 4.7, Requirements, Terminology, and Test Code for Instrument Transformers.

of a three- phase- to-grou nd or a line-to-ground fault wher where e capacitor banks are grounded. Applications which expose general-purpose circuit breakers to this capacitor bank discharge current should be checked to determine tha t the transie nt inrush current magnitude an d frequency do not ex exce ceed ed the values established. establishe d. Values are under consideration in t h e N E M A High-Voltage Power Circuit Breaker Technical Committee for eventual inclusion in the notes to Tables 1 through 4A of ANSI C37.06-1979. Th e tot al discharge current (peak) of all banks behind the breaker is equal to the algebraic sum of of t he indivi dual banks o off capacitors. Neglecting resistance, the discharge current of an individual capacitor bank is equal to6:

4.10.2 Exposure to Total Capacitor Bank

Discharge Current Discharge Current.. In a statio n where parallel capacitor banks are located on, or essen essential tially ly on, a bus, any circuit breaker connected connected to the bus may be expos exposed ed during faults t o th e tota l discharge current of all the banks located behind the breaker. In Fig 11 11,, PCBZwill be subjected to this total discharge current with a fault occurring at location A . The worst case, orwith highest capacitor discharge occurs a bolted three-phase faultcurrent, where capacitor banks ar e ungrounded an d for a case

where

I = crest value of disch discharge arge curren t E , , = rms phase-to-phas phase-to-phase e voltage C = capacitance per phase of individual bank L = inductance per phase between capacitor bank and fault location.

"See Appendix B.

29

Authorized licensed licensed use limited to: University of Massachusetts Boston. Downlo Downloaded aded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

ANSI/IEEE

C37.012-1979

APPLICATION GUIDE FOR CAPACITANCE CURRENT SWITCHING F O R

(This inductance is primarily made up of bus conductors and any additional inductance added to the bank for limiting the inrush inrush currents.) If there are n capacitor banks of approximately equal capacitance and separated by by a n approxima appro ximately tely equal inductanc e to the fault,

maining on t he bus section to be deenergi deenergized. zed. In the example of Fig 11,  11, this means means th at the tie circuit breaker must be capable of switching two banks of capacitors in parallel with two banks of capacitors on the source side. Another solution is to coordinate if possible

then the iscur approximately eqtotal ual todischarge th e sum ofcurrent th e crest rent of of each bank or n times tha t of of one bank. Th is is demonstrated as follows:

th e clearing times so th at the tie circuit breakbreaker is always first to clear to avoid the capacitor switching duty.

In addition to the checking of the crest current, it may be necessary necessary also to check check the rate of change of the discharge current with the manufacturer. The transient discharge current passing through a circuit breaker must also be examined for its effects upon the linear couplers and bushing bushing curren t transformers. transformers. T he discharge currents may substantially exceed the magnitudes and the frequency frequency of of th e inrush currents described in 4.10.1. This occurs because the contribution may come from a number of capacitor banks banks and is not limited by t he inrush impedance seen when energizing a bank of capacitors. ca pacitors. The formulas formula s giv given en in 4.10.1 for determining the induced voltages in the linear couplers or in bushing current transformers also may be used used fo r determinin g th e effects effec ts of of the discharge currents.

4.10.3 Exposure to Capacitive Switching Duties During Fault Fault Switc hing. Where parallel banks of capacit ors are located on bus sections in a station, caution must be exercised ercis ed in th e faul t switching sequence sequence so t h at the last circuit breaker t o clear is not subjected to a capacitive switching duty beyond its capability. Th is is especial especially ly a concern for a circuit breaker used as a bus section tie breaker with capacitors located on both sides of the circuit breaker as shown in Fig 11, 11, PCBi. T h e worst worst case occurs occurs in a station where the bus section itie circuit breaker is last to clear the bus for a fault that leaves one or more phases of the capacitor banks fully energized. In this situation, the bus tie circuit breaker must be properly equipped and rated for the parallel switching of the capacitor banks re-

4.11 Effect of Load. The situation can occur where a circuit breaker is called upon to switch a combination of of a capacitance cu rren t and a load current. The circuit breaker will have the required switching capability if the tota l curren t does not exceed exceed the ra ted con tinuous current of the circuit breaker and either (1) he power factor is at least 0.8 leading, or (2) the capacitance current does not exceed the ra ted capacitan ce switching curre nt of of the circuit breaker. Where the above conditions are exceeded, the capability an d performance of of th e circuit breaker is not defined by the standards and the manufacturer should be be consulted. The test procedure in ANSI/IEEE C37.09-1979 oes not require the test circuit to have a power factor below 0.8 lagg lagging ing o orr leading to test the continuous current switching rating of the circuit breaker. When the power factor is below 0.8 leading, the voltage may be sufficiently out of of phase w ith th e cu rrent t o cause unacceptable restriking. T he s ituatio n will will b be e more severe if there is also a bank of capacitor s located on th e source side of th e circuit breaker. 4.12 Effect of Reclosing. Up to twice normal inrush curr ents a re possible possible when when reclosing reclosing is applied to a circuit breaker sw itching capacitance loads. When capacitor bank current is interrupted a t or near a normal current zero, zero, the voltage remaining on the bank may be near peak value. Reclosing a circuit breaker against such a charged capacitor bank may produce high inrush current. When a capacitor bank is connected to the load side of a feeder breaker equipped with autom atic reclosing, reclosing, high inrush c urren ts can be avoided by isolating the capacitor bank from other loads after the circuit breaker is tripped and before reclosing. The device used for regular capacitor bank switching can be employed emplo yed for isolation. isolation. Th is technique is par-

30

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

AC HIGH-VOLTAGE CIRCUIT BREAKERS RATED ON A SYMMETRICAL CURRENT BASIS

ticularly recommended where other capacitor banks are connected connected to the same statio n bus bus.. A second technique to avoid high inrush currents during reclosing is to increase reclosing time delay. Normally, the discharge resistors inside each capacitor u ni t wil willl reduce residual voltage as specified in ANSI/IEEE Std 18-1968, Shun t Power Capaci Capacitors. tors. Discharge curves are available from the capacitor supplier and should be consulted where reclosing reclosing time delay is applied. 4.13 Resistor Thermal Limitations. For cir-

cuit breakers breakers equipped equipped with arc sh un tin g resistors the thermal capability of th e resistor resistorss must be considered in determining the time interval between capacitance current switching operations. (1) For general-purpose circuit breakers the shunt resis resistors tors have th e thermal capability speci speci-fied in ANSI/IEEE C37.04-1979. ( 2 ) Definite-purpose circuit breakers designed for shunt capacitor bank or cable switching may not have arc sh unt ing re resisto sistors rs rated for reclosing duty If capacitance current switching field tests are pla nned which exceed exceed th e number of oper oper-ations in l ) , r which utilize a definite-purpose circuit breaker (2), the manufacturer should be consulted regarding the frequency of operations. 4.14 Current Pause Method.

A current paus pause e

method of of demonstrating capaci tance current switching performance is described in ANSI/ IEEE C37.09-1979.7

5. Considerations of Capacitance Currents and Recovery Voltages Under Fault Conditions The requirements, preferred ratings and tests for capacita capacitance nce switching are based on switching operations in the absence of faults. It is sometimes required, however, that a circuit breaker interrupt a ca capacit pacitive ive circuit circuit under faulted con7T he backg backgroun round d and mathematics involved in this

ANSI/IEEE C37.012-1979

ditions. (An example is a transmission line circuit breaker which must interrupt fault current in one phase and capacitive capacitive current in t he oth er two phases.) T The he presence of a fault faul t can increase the value of of both the capacitance swi switchin tching g curren t and recovery voltage above the val values ues recognized in the standards for the unfaulted condition. [ 61 5.1 Reasons for Successful Circuit Breaker Operation. Operati on. Circuit breakers have b been een successful in interrupting capaci capacitive tive circuits circuits under faulted conditions. Reasons for successful operation include : (1) The highest values of recovery voltage and current usually usually do no t occur simult simultaneou aneously. sly. A circuit condition which causes a high voltage may occur with a curren t value which is less than normal, and in like manner a high current may occur with a voltage less than rated. ( 2 ) Whe When n switching a capacitor bank, with its

neutral, or th e sy system stem neutral neutral,, or both, ungrounded, interruption of the first phas phase e res results ults in a single-phase circuit in the uninterrupted phases. Thus, since t he t wo poles poles o off the circuit breaker are in series at final interruption, the voltage across each pole is less than rated. 5.2 Switching Open Wire Transmission Lines Under Faulted Conditions. The voltages and currents which occur when switching a faulted transmissio tran smission n line are affected by the circuit parameters and th e sequence iin n which the three phases interrupt. ANSI/IEEE C37.09-1979, 4.13.3.3 lists the maximum value of recovery voltage for switching an unfaulted transmission line as 2.4 E (phase-to-ground). W Wh hen switching a faulted line this value may be exceeded, as may be the rated capacitance switching current value as listed in ANSI C37.06-1979. The values listed in Tables 4   and 5 are typical of those which may occur on t he unfaulted phases when switching a transmission line with a single phase-to-ground fault. Table 4 lists the voltages and currents for a 242 kV system, and Table 5 lists the values values fo r a 550 kV system. The highest voltage occurs on the unfaulted phase which interrupts prior to the faulted phase. The highest current occurs on the last phase to interrupt when the faulted phase is

the first to interrupt. The current for this case is not a sine wave but is distorted, as shown in Fig 1 2 . Under these conditions, th e voltag voltages es and

currents may exceed the 2.4 E

method are given in Appendix B.

phase-to-

31

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

ANSIIIEEE

C37.012-1979

APPLICATION GUIDE F O R CAPACITANCE CURRENT SWITCHING SWITCHING F O R

RECOVERY VOLTAGE

C A P A C I TI TI V E C U R R E N T

-1

l2.18 X E (phase-to-ground) 21.77 Rated Current A)

CAPACITIVE CURRENT

RECOVERY VOLTAGE

32.74 E,

(phase-to-ground)

41.09 Rated Current B)

Fig 12 When nF Fault aulted ed Phase (A) Recovery Voltage and Current for Last Phase to Clear Whe is First in Sequence to Clear, (B) Recovery Voltage and Current for First Phase Clear r When Faulte d Phase i s Second in Sequence to Clear to Clea

32

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

AC HIGH-VOLTAGE CIRCUIT BREAKERS RATED ON A SYMMETRICAL CURRENT BASIS

ground voltage and the rated current values on which the design tests are based. In Tables 6 and 7, the values of recovery voltages as a rat ratio io t o Em,, phase-t pha se-to-g o-grou round) nd) and currents (as a ratio to rated current) are listed for a phase-to-phase phase-to-phase grounded fault. For the phase-to-phase fault condition, the recovery voltage and capacitance current are les lesss severe than fo r th e phase-to-p phase-to-phase hase grounded grounded fault condition.

5.3 Switching Capacitor Banks Under Faulted

Conditions. The voltages voltages and currents current s whic which h can occur when switching a faulted capacitor bank depend upo n th e grounding grounding conditi conditions, ons, whether the fault is to the bank neutral or to ground, and on th e sequence in which which the three pha phases ses interrupt. 4.13.3.3 of ANSI/IEEE C37.09-1979 lists the maximum value of recovery voltage in switching an unfaulted shu nt capacitor bank as (phase (ph ase-to -to-gr -groun ound). d). When swit switchin ching g a 3.0 Em, faulted bank, this value may be exceeded, as may the rated capacitance switching current value. Typical recovery voltages and currents for a three-phase capacitor bank are shown in Tables Tables 8, 9 and 10. Table 8  lists reference condition values for an unfaulted balanced system. Table Table   9  lists values values for a bank with one phase shorted to neutral and Table 1 0  lists values for a bank with one phase shorted to ground. It shoul should d be noted that all recovery voltages listed will be experienced experien ced one-half cycle after curren t interruption. It is unlikely unlikely that t he first first phase phase to interru pt will will be stressed stressed to t he voltag voltage e values values listed since the other two phases will normally interru pt before one-half cycle elaps elapses. es. The voltages and currents obtained with the reference condition shown in Table 8  agree with the 3.0 Em, (phase-to-ground) voltage voltage listed in 4.13.3.3 of ANSI/IEEE C37.09-1979, and the current value (1.0) corresponds to rated capacitance switching current. Although the voltage across acr oss the last phases phases to interrupt when when a t least one of t he neutrals (source or bank) is ungrounded can reach reach 3.46Em, (phase-to-ground) the two phases are in series so that neither is stresse stressed d t o 3.0 Em, (phase-to-ground) volta voltage. ge. A fault to neutral on one phase of a threephase capacitor bank produces higher recovery voltages and currents when at least one neutral is ungrou nded. Relative values values are listed in Table Table   9.  9. is  Ifsubjected an unfaulted is the(phase-to-ground) first to interrupt, it subjec ted to aphase 3.46 Em, recovery voltage until the second and third

ANSI/IEEE ~37.012-1979

phases interrupt. The highest capacitive current (3.06 times the rated value) is experienced in the faulted phase when it interrupts first. Following this interruption, the 3.46 Em, (phase-to-ground) recovery voltage is impressed across the interrupters in the two remaining phases. A phase-to-ground fault produces the most severe seve re conditions when th e source is ungrounded and the bank neutral is grounded. Relative 10..   If an unfaulted values are listed in Table 10 phase is the first to interrupt, the current may reach 1.73 times the rated current value and the recovery voltage 3.46 Em, (phase-toground). The remaining phases are subjected to the same current, but upon interrupting, share the 3.46 E (phase-to-ground) recovery voltage. When the faulted phase is the first to interrupt, the current may be 3.06 times the rated current value and the recovery voltage 3.0 Em, (phase-to-g (phas e-to-ground round ). The second phase to interrupt will have a lower current but a higher recovery voltage of 3.46 Em, (phase-toground) which will be shared with the third phase.. If t he faulted phase reignites, phase reignites, one of of the unfaulted phases will then interrupt and the conditions will be as previously described when a n unfault unfaulted ed phase phase was was th e first to interrupt. For phase-to-phase ground faults, or phaseto-phase ungrounded faults, with the source grounded and the bank neutral ungrounded, recovery voltages and currents are no more severe than for the standard no-fault condition.

5.4 Switching Cables Under Faulted Conditions. The normal frequency capacitance currents and recovery voltages on a faulted cable circuit will be the same as for a grounded capacitor bank under faulted conditions.

5.5 Requirements. Specific tests for capacitance switching under fault conditions are not required. With no faults, the conditions of Section 4 apply. However, a related requirement of the circuit breaker, which accompanies the capacitance switching switching rating, rating, is tha t the breaker breaker must be capable of interrupting the capacitance current under faulted conditions within the following restrictions. (1) Wi With th faults, th e interrupting time and th e rated transient over-voltage factor of ANSI/ C37.04-1979 IEEE be exceeded. 2) The recovery may voltages and capacitance currents on the unfaulted phases of overhead

33

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

ANSI/IEEE

C3 7.0 2-19 79

APPLICATION GUIDE FOR CAPACITANCE CURRENT SWITCHING FOR

transmission transmissio n lines must be within the limits specified in Tables 4, 5, 6 and 7 of this guide. (3) The recov recovery ery volt voltages ages and capacitance currents on the unfaulted phases of shunt capacitor banks or cables with single phase faults must be within the limits specified in Tables 9   and 1 0 of this guide. (4) The source m ust have a coefficient of grounding of 80 percent as defined in ANSI/ IEEE Std 100-1 977, IEEE Standard Dictionary of Electrical and Electronics Terms. 5 ) With ungrounded capacitor banks, the condition with one phase of the capacitor bank shorted is not cover covered ed in this application guide guide.. Applications outside the above limits should be referred to the manufacturer for consideration. While Whi le th e values of recovery voltage and current shown in Tables 4, 5 , 6 and 7 are related t o specific specific system voltages voltages with specific specific system parameters as noted, the results are generally applicable applicabl e t o any rated voltage. 5.6 Examples of Application Alternatives. Other application opt ions avail available able are: are: (1 ) Use a circuit breaker of a higher rating in those cases of ground faults on ungrounded systems where th e recovery voltage and current, or both, exc exceed eed the requirement requirementss of ANSI/IEEE C3 7.04-1979. 7.04-1979. (2) Reduce the capacitor bank size so that the current under faulted conditions does not exceed the rated capacitance switching current of th e circuit breaker breaker.. (3) Use a high speed switch to ground the source or capacitor bank neutral before switching the capacitor bank under faulted conditions. (4 ) Change the capacitor bank configuration from an undergrounded Y t o a A on systems 1 5 kV and below. The capacitor fusing must be checked.

Standards Institute, apply.

Inc, t he revisio revision n sh shall all

ANSI/IEEE C37.010-1979, Application Guide fo r AC High-Volta High-Voltage ge Circuit Circuit Breakers Rated o n a Symmetrical Current Basis. ANSI/IEEE C37.04-1979, Rated Structure for AC High-Voltage Circuit Breakers. ANSI C37.06-1979, Schedules of Preferred Ratings and Related Required Capabilities for AC High-Voltage Circuit Breakers Rated on a Symmetrical Symmetri cal Curre Current nt Basis. Basis. ANSI/IEEE C37.09-1979, Test Procedure for AC High-Voltage Circuit Breakers. ANSI/IEEE C57.13-1979, Requirements, Terminology, minol ogy, a nd Test Code for Instrument Trans Trans-formers.

7 . References [ 11 GABRIELLE, A. F., MARCHENKO,

P.P., and VASSELL, G.S. Electrical Con-

stants and Relative Capabilities of BundledConductor Transmission Lines. Lines. IEEE Transactions on on Power Apparatus and Sys tems vol 83, J a n 1964, 1964, p p 78-92. [2] STEVENSON, William, Jr. Elements of Power Sys tem Analysis. New York: McGrawHill, 1962, p p 114-133.

[ 31 Electrical Transmission and Distribution

B o o k . East Pittsburgh, Pa.: Westinghouse Electric Corporation, 1950.

[ 41 IEEE Committee Report Bibliography on Switching of Capacitive Circuits Exclusive of

Series Capacitors, IEEE Transactions on Power Apparatus and Systems vol PAS 89, Jun /J ul 1970 1970,, pp 1203-1207.

6. Revision of

[ 5 ] PFLANZ, H. M. M.,, and LE ST ER , G. N.

American National Standards Referred to in this Document

Control of Overvoltages on Energizing Capacitor Banks, Paper T 72-541-1.

When the American National Standards referre refe rred d to i n thi s document are superseded superseded by revision sion approv approved ed by t he American National a revi

[ 6 ] J O H N S O N , I.B.; SCHULTZ, A . J . ; SCHULTZ, N.R.; and SHORES, R.B., AIEE Transuction, p t 111,1955 pp 727-7 727-736. 36.

34

Authorized licensed licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

ANSI/IEEE C37.012-1979

AC HIGH-VOLTAGE CIRCUIT BREAKERS RATED ON A SYMMETRICAL CURRENT BASIS

Table 4 Recovery Voltages Voltag es and Curr Current entss on Unfaulted Phases of 242 k V Open Wire Wire Tran Transmission smission Line wit with h a Phase-to-G Phase-to-Ground round Fault Firstt Firs hase to Interrupt Fault at Faul Faultt at Source End Remo te End 8) 8) I E Z E

Faulted phase first

Second Phase to Inter rupt Phase Faultt at Faul Fault at Source End Rem ote End 8) 8) E E I

Source Impedance equivale equivalent nt &A)

XO x

(5)

1.77

1.14

1.80

1.13

2.0 2.0

1.58

2.33 2.33

1.56

40

3.0

1.77

1.18

1.85

1.13

2.0

1.72

2.37

1.56

30

3.0

1.88

1.44

1.92

1.13

40

3.0 3.0

2.04

1.18

1.88

1.13

30

3.0

40

3.0

30

3.0

2.55

1.17

2.48

1.13

2.74

1.22

2.45

1. 13

2.13

1.14

2.06

1.13

2.44

1.17

2.27

1.13

2.17

1.19

2.07

1.13

2.54

1.22

2.28

1.13

NOTES:

Third Phas Phase e to Interrupt Fault at Fault at Source End Remote End (8) 8) I I E E

Faulted phase secon second d

Faulted phase third

(1 ) Current is interrup ted in no rmal sequence, at succeeding current zeros. (2 ) T Tests ests made at a rated line chargi charging ng current o f 16 0A at 242 kV. charging ing curren t for 242 kV; CJ CJC, = 2.0; line represented represented by (3) Line length chosen to provide 16 0A line charg distribute d paramet parameters, ers, comple tely tran transposed sposed ( equal copuling between phases phases). ).

(4 ) Source impedance chosen to give a three-phase ungrounded fault current at the circuit breaker terminals as shown.

( 5 ) Source coefficient of grounding is 80% for

/X, 4 3.0.

(6 ) For the fault a t th e rem ote end, it is ass assumed umed that th e remote end circuit brea breaker ker interrupts first, first, a and nd that the voltages and currents imposed on it are the same as for the fault at the source end. The reported values are the voltages and currents imposed on the source end circuit breaker with the remo te end circuit breaker already cleared cleared.. (7 ) These va values lues were obta ined by digital comput er and tra nsient netw ork analyzer studies.

(8 ) The numerical values listed for E and I are ratios of the peak value of transient recovery voltage to Emax Ema x (phase-to-ground), and the ratio of the peak value of switched capacitance current to the peak value of rated capacitance switching current.

35

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

ANSI/IEEE C37.012-1979

APPLIC APPLICATION ATION GUIDE FOR CAPACI CAPACITANCE TANCE CURRENT SWITCHING SWITCHING FOR

Table 5 Recovery Voltages and Curr Current entss on Unfaulte Unfaulted d Phases of 550 kV Open Wire Transmission Line with a Phase-to-Ground ault First Phase to Interrupt Fault End at Source

E

8)

Fault at Remote End

E

I

Second Phase to Interrupt

8)

I

Faulted phase phase first

Fault End at Source

8)

E

Third Phase to Interrupt

Fault at Remote End

8)

(8)

I

(5)

1.05

1.80

1.11

2.16

1.56

2.18

1.76

40

1.0

1.65

1.09

1.82

1.11

1.66

1.66

2.18

1.17

40

3.0

1.70

1.12

1.77

1.12

1.87

1.67

1.21

1.75

20

3.0

2.14

1.05

2.21

1.11

40

1.0

1.82

1.09

1.98

1.11

40

3.0

1.98

1.12

2.05

1.12

20

3.0

40

1o

40 20

3.0 3.0

1.08

2.74

1.13

2.74

1.09

2.7.4

1.14

2.74

1.11

2.12

1.05

2.21

1.11

2.08

0.95

2.41

1.08

2.12 2.14

1.09

2.21 2.20

1.10

2.43 2.43

1.1 3 1.14

2.44 2.44

1.09

NOTES:: NOTES

E

X1

2.06

2.84

Faulted phase second

I

equi equival valent ent (kA)

E

0.95

1.12

(8)

E

Fault at Remote End

o

I

2.36

1 .1 2

Fault End at Source

Source Impedance

Faulted pha phase se third

1.11

(1) Current is interrupted in normal sequence, tha t is at eac h succeeding succeeding curren t zero. charging ng current of 400A at 550 kV. (2) Tests made at a rated line chargi (3 ) Line Line length chosen t o provide a r ated line charging charging curr ent of 400A at 550 kV; CJ CJC, C, = 2.0; line represented distributed parameters, complete ly transposed (equal coupling coupling between phases). three-phase hase ungrounde d fault cur rent a t breaker breaker terminal terminalss as shown. 4) Source impedance chosen to give a three-p (5 ) Source coefficient of grounding is 80% for

I

< 3.0.

(6) For the fault at the remote end, it is assume assumed d tha t the r emote end circuit brea breaker ker interrupts first, first, and that the voltages and currents imposed on it are the same as for the fault at the source end. The reported values are the voltages and currents imposed on the source end circuit breaker with the rem ote end circu it breaker breaker already cleared. cleared.

7 ) These values values were obtained b y digital comp uter a nd transient netw ork analyzer studies. voltage e to ( 8 ) The numerical values listed for E and I are ratios of the peak value of transient recovery voltag Em, (phase-to -ground), and the rat io of the peak value of switched capacitance current to the peak value of rated capacitance switching current.

36

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

ANSI/IEEE C37.012-1979

AC HIGH-VOLTAGE CIR CUm BREAKERS RATED ON A SYMMETRICALCURRENT BASIS

Table 6 Recovery Voltages Voltag es and Curre Currents nts on Unfaulted Phases of 242 kV Open Wir Wire e Transmission Line wit with h a PhasePhase-to-Pha to-Phase se Grounded Fault Firstt Phase t o Cle Firs Clear ar Fault at Fault at Source End Rem ote End

E

8)

I

E

8)

I

Faulted phase first

Faulted phase first 2.34

1.04

2.28

1.03

2.36

1.0

2.33

1.03

NOTES:

Second Phase t o Cle Clear ar Fault at Fault at Source End Remote End 8)

E

(8)

I

E

1.68

1.06

1.62

1.01

1.63

1.08

1.6

1.03

Faulted phase second

Third Phase to Cle Clear ar Fault at Fault at Source End Remote End (8) (8) I I E E

Fault e d phase th ird

Source Impedance Equivalent ( k V)

XO

40

3

20

3

(5)

2.28

1.55

2.37

1.33

40

3

2.37

1.62

2.45

1.32

20

3

40

3

20

3

Faulted phase second

Faulted phase third

(1 ) Current is interrup ted in normal sequence, at succeeding current zeros. (2 ) Tests made at a rated line charging current of 160 A at 242 kV. kV. (3 ) Line length chosen t o provide 16 0A line charging current fo r 242 kV; C, C,/C /C,, = 2.0; line represented by distributed parameters, completely transposed (equal coupling between phases). (4 ) Source impedance chosen to give a three-phase ungrounded fault c urrent a t circuit breaker terminals as shown.

( 5 ) Source coefficient of grounding is 80% for XJX,

4

3.0.

(6) For the fault at the remote end, it is ass assumed umed that the remote end circuit breaker interrupts first, first, and that the voltages and currents imposed on it are the same as for the fault at the source end. The reported values are the voltages and currents imposed on the source end circuit breaker with the remote end circuit breaker already cleared. (7) These values values were obtaine d by digital computer and transient network analyzer studies.

(8 ) The numerical values listed listed for E and I are ratios of the peak value of transient recovery voltage to Emax (phase-to-ground), and the ra tio of the peak value of switched capacitance current t o the peak value of rated capacitance switching current.

37

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

ANSI/IEEE

C37.012-1979

APPLICATION

GUIDE FOR

CAPACITANCE CURRENT SWITCHING F O R

Table 7 Recovery Voltages and Currents on Unfa dte d Phas Phases es of 550 kV Open Wire Transmission Line with a Phase-to-Phase Grounded Fault First Phase to Clear Fault at Fault at Source End

E

(8)

I

Remote End

E

8)

I

Faulted phase phase firs firstt

Faulted phase phase first

2.08

0.87

2.33

1.03

2.34

1.06

2.37

1.04

2.34

1.06

2.37

1.1 3

NOTES:: NOTES

Second Phase to Clear Fault at Fault at Source End 8)

Remote End

E

I

E

1.98

0.87

1.7

0.9 0.98 8

1.65

1.06

1.6

1.04

1.63

1.06

1.56

1.05

Third Phase to Clear Fault at Fault at Source End

8)

(8)

E

I

Remote End

E

(8)

Source Impedance

O

Equi Equival valent ent

X1

40

1

40

3

20

3

I

Faulted pha phase se third

Faulted phase phase second

Faulted phase second

(kV)

(5)

2.05

0.92

2.3

1.52

40

1

2.3

1.75

2.3

1.52

40

3

2.3

1.64

2.35

1.5

20

3

40

1

40

3

20

3

Faulted phas phase e third

(1) Current is is interrupted in normal sequence sequence,, tha t is at ea ch succeeding succeeding current zero. (2) Tests made at a rate d line charging charging current of 400A at 550 kV. (3 ) Line Line length chosen to provide a r ated line charging charging curr ent of 400A at 550 kV; C,/C, = 2.0; line line represented distributed parameters, completel y transposed (equal coupli coupling ng between phases) phases).. (4) Source impedance chosen to giv give e a threethree-phase phase ungrou nded fa ult cur rent a t breaker termin terminals als as shown.

( 5 ) Source coefficient of grounding is 80% for

/

4 3.0.

assumed med that the remote end circ circuit uit break breaker er inter rupts first, and (6) or the fault a t th e remote end, i t is assu

tha t th e volta voltages ges and currents impo imposed sed o n it are t he same as for th e fault at t he source end. The reported values values are the voltages voltages and currents imposed on the source end circuit breaker with the remo te end circuit breaker already cleared cleared..

values were were obtain ed by digital digital compu ter and transient n etwork an alyzer stud studies. ies. (7) hese values voltage e to (8 ) The numerical values listed for E and I are ratios of the peak value of transient recovery voltag Em, (phase-to -ground), and th e ratio of the peak value of switched capacitance current to the peak value of rate d capacitance switching switching current.

38

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

AC HIGH-VOLTA HIGH-VOLTAGE GE CI RCUlT BREA KERS RATED ON A SYMMETRICAL SYMMETRICAL CURRENT BASIS

ANSI/IEEE C37.012-1979

Table 8 Recovery Voltage Volta ge and Currents on Unfaulted Balanced Shunt Capacitor Bank (Reference Condition)

B A NK

Grounding Source

grounded grounded ngrounded ungrounded

Bank

grounded ungrounded grounded ungrounded

First Phase Phase to Interrupt Phase

a a a a

Remaining Phase or Phases to Interrupt

Voltage (VI (1)

Cur ren t

Voltage

(A) (2)

(1)

2.0

1.0 1.0 1.0

3.0 3. 0

3.0

1.0

VI

b or c b and c b and c b and c

2.0

3.46 3. 46

3.46

Current

A)

Two Interrupters in Series

2)

1.0

0.86 0. 86 0. 86

no Yes Yes Yes

NOTE:: T he value NOTE valuess were obtained b y analy analysis sis and fro m studies on a miniature system. (1 ) Ratio peak recovery voltage to E

(ph aseto-groun d).

value ue of rated capacitance switching curren,t. (2) Ratio of peak value of switched capacitance current to th e peak val

39

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

ANSI/IEEE C 3 7.012-1 79

APPLICATION GUIDE FOR CAP CAPACM ACM'AN 'ANCE CE CURRENT SWITCHING FO R

Table 9 Recovery Voltage and Currents on Unfaulted Phases of Shunt Capacitor Bank with Fault to Neutral on One Phase

CAPACITOR B A N K ONE PHASESHORTED

Firs t Phase to Interrupt

Grounding Source

Bank

grounded *grounded *ungrounded *ungrounded

grounded ungrounded grounded ungrounded

grounded *grounded *ungrounded *ungrounded

grounded ungrounded grounded ungrounded

Phase

a a a a C

c c

Voltage Voltage

Current

(1)

(2)

Remaining Remainin g Phase or Phases to Inter rupt Phase

Voltage

Current

(1)

(2)

Two Interrupters in Series

2.0

1.0 1.73 1.73 1.73

b bandc b and c b and c

2.0

3.46 3.46 3.46

1.0 1.73 1.73 1.73

no Yes Yes Yes

fault 3.0 3.0 3.0

fault

a or b aandb aand b aand b

2.0 3.46 3.46 3.46

1.0 0.86 0.86 0.86

no Yes Yes Yes

3.46 3.46 3.46

3.06 3.06 3.06

*Consultt manufact urer fo r these applications. *Consul applications. NOTE: These values values were obtained by analysis analysis and fr om studies on a m iniature system.

(1)Ratio of peak recovery voltage to E

(p hae -to- gr ound ).

(2) Ratio of peak value of switched capacitance current to th e peak value of rated capacitance switching current.

40

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

AC HIGH-VOLTAGE CIRCUIT BREAKER BREAKERS S RATED ON A SYMMETRIC SYMMETRICAL AL CURRENT BASIS

ANSI/IEEE C37.012-1979

Table 10 Recovery Voltages V oltages and Currents on Unfaulted Phases of Shunt Capac Capacitor itor Bank with Fault to Ground on On One e Ph Phas ase e

BREAKER 0

C A P A C I TO TO R B A N K

b

-

GROUND ON BANK

C

First Phase to Inter rupt

Grounding Source

-

Bank

grounded grounded *ungrounded *ungrounded

grounded ungrounded grounded ungrounded

grounded grounded *ungrounded *ungrounded

grounded ungrounded grounded ungrounded

Phase

a

a

a a

Voltage

Curr ent

(1)

(2)

2.0

1.0

Remai Remaining ning Phase Phase or Phase Phase t o Interrupt Pha Phase se

b

Voltage

Current

Two Inte rrup ters

(1)

2)

in Series

2.0

1.0

2.2 3.46 3.0

0.88 1.73 1.0

b b and c b and c

2.0 3.46 3.46

1.73 0.86

fault fault 3.0

fault fault 3.06 1.00

a or b a and b a and b a and b

2.0 2.6 3.46

1.0 0.86 0.86

3.0

3.46

0.5

0.86

*Consult manufac turer fo r these applicati applications. ons. NOTE: These values values were obtained by analysi analysiss and from stud ies on a miniature system.

(1) Ratio of peak recovery voltage to E

(phase-to-ground).

(2) atio of peak value of of switched capaci tance current to th e peak valu value e of rated capacitan ce switching switching current.

41

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

ANSI/IEEE C37.012-1979

Appendix A Example of Open Wire Transmission Curren Currentt Calcu C alculatio lation n (These Appendixes are not a part of ANSI/IEEE C37 .01 2-1 979 , A American merican National National Standard Application Guide for Capacitance Current Switching for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis.)

The method which follows is based essentially on the material contained in Reference [ l ] The capacitive reactance can be calculated for single-circuit transmission lines using ' = Xa(eq)rx, '

(Eq A l l

where X' = capacitive reactance per phase of an open wire transmission line, in meg-

ohms per mile conductor component of Xa(eq)' = equivalent capacitive reactance per phase in a bundle for 1 t spacing 0 X,' = 0.06831 og,, D (ML?/mi) fs

with

f , = system frequency, in hertz D = equivalent phase spacing, in feet

or for a single-circuit single-circuit line, (Eq A2) = v d a b d bc bc dca where dab dbc,and d,, are the distances distances in in fee t 'between 'betwe en conductors. Also.

for n conductors in a bundle configuration. 60 Xa' = 0.06831 og,, MQ/mi) s

X12' = O.0683l6O log,, s

X13' = 0.06831 Xln'

where

60 s

all,

(ML?/mi)

og,, d13 (MQ/mi)

60 0.06831- log10 d l , (ML?/mi) s

bundle. and for a three-conductor bundle.

Sample Calculation. Determine the line charg-

ing current that a circuit breaker must interrupt for application on a 55 0 kV system. The line parameters are Voltage Length Phase spacing Subconductor Subconductor spacing

=

distance between conduc-

18 in (457 mm)

As a first appro ximation, Fig 1 is used by entering the curve at 550 kV and determining the current as 2.27A/mi. The charging current is thus IC = (2.27)(150) = 340 A

If a more accurate accur ate calculation is required, require d, Eq 1 can be evaluated as follows. The line is represented by Fig Fig A l , and the equivalent phase spacing is D (38) = 47.9 f t Then 60 X,' = 0.06831 60 log,, 47.9 = 0.115 ML?/mi

=v(3&)(76)=

The conductor radius is 0.0668 ft , making making 0 oglo X,' = 0.06831 = 0.0803 Mn/mi 0 0.0668 But for a two-conductor bundle,

r l = radius of one conductor in bundle, in feet

dlZ,d13, dlZ, d13, .. , dln

550kVphase-to-phaserms 150 mi (241.5 km) 38 f t (horizontal) (11.6 m) two 178 0 kcmi kcmill ASCR per phase

Since d12= 18/12 t

tors in th e bundle, in feet For a single conductor, (Eq A4) Xa(eq) = Xa for a two-conductor bundle,

X12' = 0.06831 0 log,, 60 Therefore,

8 12

= 0.012

MO/mi

43

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

ANSI/IEEE C37.012-1979

APPLICATION GUIDE FOR CAPACITANCE CURRENT SWITCHING FOR

I K

38ft

__I,

38 t

4

1

1

1

I

I

A

8

0

0

C

Fig A I - 0.0803 ,-

Xa(es)

The GMR for a 1780 kcmil ACSR conductor is 0.0536 f t . Substituting,

.012 2

= 0.03415 Mi22/mi

Then from E q A l , X' = 0.03415 + 0.115 = 0.1492 MSl/mi

L

=0.1529 n / m i

which corresponds to a current of 319 A . The estimated current of 340 A from the curve is slightly on t he conserv conservative ative side. side. If the Ferranti effect is considered, the value of the t he inductive reactance reacta nce per mile is required. Again from reference 113, xL

=

Xa ( e q )

Xd

Then XL

=

0.1529

0.469 = 0.622 n / m i

Substituting in t he Ferranti effect equations of of Section 4.6.1, he current is

where = lIc l [1.03] x d

= 0.2794 %loglo D

fi/rni)

and GMR is the geometrical mean radius in feet, the other symbols as before.

where lIc'l= 319 A. The corrected current is 330 A . The final step is to consult consult th e table of ratings to verify the capability of the circuit breaker.

44

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

AC HIGH-VOLTAGE CIRCUIT BREAKERS RATED ON A SYMMETRICAL CURRENT BASIS

ANSI/IEEE C37.012-1979

Appendix B Basic Relations During Capacitance Capacitanc e Current Current Switching Switc hing

Foreword The switching of capacitive currents can be a severe duty for the circuit breaker. Such currents, the charging current of an unloaded transmission line or cable, or the load current of a static capacitor bank are, in most cases, a maximum of a few hundred amperes. Since the capacitance can retain a voltage charge, the capacitance current arc is usually interrupted at a very early current zero after the circuit breaker contacts separate. After interruption, the normal frequency alternation of the voltage on the source side of the breaker results in a recovery voltage across the circuit breaker contacts which, one half-cycle after interruption, can approach two to three times crest line-toneutral voltage. A breakdown across the contact gap during this interval will produce transient overvol overvoltages. tages. The maximum magnimagnitude of such overvoltages may generally be related to the time interval between the interruption and the occurrence of the breakdown across the contacts by use of generalized circuit breaker operating characteristics. This Appendix has been prepared in an attempt t o provide provide the bas basis is for an understanding understanding of the Standard for Capacitance Current Switching, its requirements, and the methods suggested for demonstration of these requirements.

B1. Capacitance Current Switching Rating

banks on the system, that is, back-to-back capacitor banks The transient overvoltage overvoltage limit during opening shall be as specified for the following categories of circuit breakers:

Design Desig n

Rate d Voltage

General purpose Definite Definit e purpose Definite Definit e purpose

All voltages 72.5 kV and below 12 1 kV and above

Rated Transient OverVoltage Fact or

3.0

2.5 2.0 2.0

This performance is demonstrated by making the required series of capacitance current switching tests with measured transient overvoltages equal to or less than allowable limits. At the option of the manufacturer, an alternative method of demonstrating performance for circuit breakers rated 121 kV and above is to make tests in which the prospective overvoltages, based on the time interval (current pause) before restrike, are less than the allowable limit. For tests where t he overvoltage overvoltage iiss to be determined by this time interval relation, the allowable time before restrike is included as part of ANSI/IEEE C37.04-1979. The derivation of these relations, considering considering th e sswitchi witching ng of shunt capacitor bank current or line charging current and considering the use of arc shunting resistors, resist ors, is presented in this Appendix.

B2. Investigation of Transient Currents When Energizing

The capacitance cur rent switching rating ratingss assigned to circuit breakers are related t o a number of factors which include the following. (1) The circuit breaker design, whether general purpose or specifically designed or modified for capacitance cu rrent switching. (2) Voltage rating, 72.5 kV and below, and

B2.1 Energizing Capacitor Banks. The equivalent circuit for energizing capacitor banks, assuming sum ing tha t th e time of clo closin sing g the switch switch occurs when the power frequency voltage is a

121 k V and above

maximum and that the time duration of the

transient is small when compared with the power frequency, is shown in Fig B1.  B1.  If this is not the case, both the transient and power

(3) System and capacitance load grounding conditions 4) The presence of other shunt capacitor 45

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

ANSI/IEEE C37.012-1979 C37.012-19 79

APPLICATION APPLICATION GUIDE FOR CAPACITANCE CAPACITANCE CURRENT SWITCHIN SWITCHING G FOR

Fig B1

frequency currents must be added together t o arrive arrive at the actual current. In the Laplace domain the general equation for th e current is

The energization current cur rent of a single deenerdee nergized capacitor bank is represented mathematically by letting C 1 = L1 = E 2 = 0 and E l = E,. Thus

-

Since Sin ce xl(sin w t ) = =

I t is noted that the above solutions are related t o a single-pha single-phase se condition. The solutions for the current for th e llast ast phase phase to clos close e on a three-phase system are identical to those derived. Currents for the second phase to close in a three-phase system will be 0.866 of those derived. If th e voltage voltage across across the switch (E, + E,) is zero, there will be no transient energization current , and if on closing closing there is a trapped charge on the capacitor bank such that E , + E , = 2 E , , the currents will be twice those derived rived in th e equation. To relat relate e t he transient transient current t o steadystate quantities the following relations are used :

____ s2 0 2

+

(Eq B4)

where ELL

nd - =i-

dt

E, L,

-=

dTi

(EqB5)

he energization current when energizing a back-to-back capacitor bank is represented mathematically by letting L 1 = E , = E,, and 8 = 0 . Substituting these values in E q B 1 ,

=-

t=--..--(.'CELL

fl

l

(Eq B6)

1 27rfC

where

orC=-

i = C=

(EqB9) (.'ELL

H z system current in capacitor bank, in kiloamperes capacitance of bank, bank , in farads

w = 27rf = 377 for a 60

77

s [ s L 2 + ( ~ / s ) ( 1 / ~W 1 2

x

and

00,

i(s)=

LL

4 3

t

'Os

= phase-to-phase voltage, in kilovolts

If C 2 is replaced by C,, , he time domain domain solution for th e current is the same as Eq B4. B4.

L,,

= inductance limiting the short-circuit

current I ,, , n kiloamperes

46

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

AC HIGH-VOLTAGE CIRCUIT BREAKERS RATE D O N A SYMMETRI SYMMETRICAL CAL CURRENT BASIS

The maximum crest transient closing current .will occur where t = m w h e n energizing a (capacitor (capaci tor bank. From Eq Eqss B4, B8, B 9, and B10 this current is

ANSI/IEEE

C37.012-1979

when energizing a back-to-back capacitor bank is 1

and combining Eqs B14 and B12 The maximum crest transient closing current when energizing a back-to-load capacitor bank is found by combining Eqs (B7) and (B9),

where i, = current in C 1 i2 = current in C 2 Combining Eq B12 and the maximum amplitude of Eq B4,

B2.2 Energizing Lines or Cables. The equivalent

circuit for energizing lines or cables until the first reflection returns from remote end is B2.  In the Laplace domain with shown in Fig B2. i = 0 and t = 0, = 1.07

E L L il

OL,

(il

i2

+ i2)

F o r o = 377 Hz,

or in the time domain,

The maximum rate of rise of current from Eqs (B5) and (B10) is

E q B13) The frequency of the oscillatory transient

d_i - E , + E t exp L dt

-F)

Eq B18)

where

2 = surge impedance of connected cable or

line, in ohms = voltage d ue t o charge trapped on line O Orr cable at time of closing The initial rate of rise of current is the same for capacitor banks or cables if the charges

Fig B2

47

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore Xplore.. Restrictions apply.  

ANSI/IEEE C37.012-1979

APPLICATION GUIDE FOR CAPACITANCE CURRENT SWITCHING F O R

trapped on each have the same magnitude. This can be seen by comparing Eqs B 1 8 ) and (B5).

+ cos u t

r in w t

J

K C

Eq B20a)

When a restrike occurs, the maximum voltage on the capacitor will be

B3. Investigation of Overvoltages Occurring When When Interrupt Interrupting ing Capacitor Bank Ba nk Current

E, (peak voltage transient) = 2 (Eq B21)

B3. 1 Capacitor Overvoltage from a Single

Restrike Through the Primary Arcing Contacts-Circuit Breaker with Arc Shunting Resistor. In the equivalent circuit of switching a capacitor bank (Fig B3), B3),  the resistor is inserted (equivalent to interruption of the primary arc current) at a voltage peak (also a current zero). The basic equation of this circuit is

,

cos w t =

1 R I + -C S I d t

cos 8

(Eq B19)

The capacitor voltage e c may be found from Eq B19 as

-

,

where 8 = degr degrees ees pr preceding eceding the restrike (curre (current nt pause) Combining this with Eq (B 20a) and solving solving for the ratio of peak transient to E m Ec (peak transient)

E,

=

2

CO S

0

1

1 + @/Xc

12

(Eq B 2 2 )

From Eq B22 the current pause may be determined for a maximum overvoltage ratio of 2 in terms of the relative value of R / X c . This has been plotted in Fig 13 of ANSI/IEEE C37.09197 9 where fo r conven convenien ience ce it is shown as the allowable current pause in degrees as a function of ( phase-t phase-to-phase o-phase operating volts) - - L, -

+ cos w t +-

XC

I

sin w t

(Eq B20)

where

E c = initial capacitor voltage (actually E , ) RfX, = oRC

For this case, E c o = E,, Eq B20 reduces to

(resistance (capacitance RI, per phase) curren t) It should be noted that for the case of no resistor R = w , that is, V L L / R I , = 0, the maximum current pause for an overvoltage of 2 or less is 120". Restrikes kes Through the B3.2 Voltage from Two Restri Primary Arci Arcing ng Contacts, ,Each After a Current Pause of 18O0-Circu 18O0-Circuit it Breaker with Arc Shunting Resistor. In this case it is desirable to

Fig B 3

48

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

ANSI/IEEE C37.012-197g

ACHIGH-VOL HIGH-VOLTAGE TAGE c I R c u m BREAKERS RATED O N A SYMMETR SYMMETRICA ICAL L CURRENT BASIS

find the limiting value of R / X , for which there may be two restrikes through the primary arcing contacts, each after a current pause of 180 without exceeding the allowable overvoltage limit of either 2.0 or 3.0 times normal phase voltage crest. In Eq B21 the maximum transient voltage that could be left on the capacitor is given for a single restrike. In this equation if 0 is NO", it becomes ,Ec1 (peak voltage transient) = E ,

( Eq B 2 6 'This voltage discharges through the resistor, according to Eq B20. When E,, (peak voltage transient of Eq B23 is substituted for E,, in Eq B20 and the current pause ot is 180 lbefor lbe fore e th e second second restrike, th e capacitor ca pacitor voltage at the instant of the second restrike will be

,Ec2

=

Em

l+(R/Xc

)2

T w o estrikes each with one half-cycle current pause will result in maximum overvoltage ratio no higher than 2.0 3.0

ITcz (peakvoltage transient) = 2E,+Ec, (Eq B25)

From Eqs B24 and B25, the limiting ratio of R / X , may be determined determined f or which which E c 2 (peak voltage transient) will not exceed the allowable levels of 2.0 or 3.0 Em

/RIc

if

is less than

more than

1.7 0

or

4.00

if

I C

is

is less than

1.0 2

or

0.43

or or

0.98 VLL lR

2.31

VLL

R

B3.3 Overvoltage from Restrikes Through the Secondary Secondar y (Resistor) Arcing Arcing Contacts-Capacitor Banks. When When the th e arc shunting shu nting resistor circuit is interrupted in a circuit breaker equipped with resistors, the equivalent circuit is as shown in Fig B4. In this equivalent circuit for restrikes through the resistor or secondary arcing contacts, the source inductance L is considered since this is a damped RLC oscillatory circuit. In the cases of restrikes through the primary

arcing contacts, the same type circuit actually exists, but it is less damped and the maximum oscillation o r "swing" "swing" of tw o times is is considered for the capacitor voltage, Eq B21. In the RLC circuit of Fig B3 B3,,   the voltage relations are ,

(Eq B24) After the second restrike, again assumlng full transient reversal of the capacitor voltage, the peak voltage transient will be

R/X,

dl

cosot = Ldt

+

RI

+

C

Solving for E , , e, = E ,

+

Eco

E,)

exp

E q B27) where /? = 1 / m f o r he case of rrel elat atiivel ely y sma smalll damping, that is, a circuit where R 2 is less than IC. (This is not usually the case in practical

49

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

ANSI/IEEE C3 7. 01 2- 19 79

APPLICATION APPLICATION GUIDE FOR CAPACITANCE CAPACITANCE CURRENT SWITCHIN SWITCHING G FOR

R

arc shunting resistor applications. Ho Howeve weverr this mathemati-cal mathemat i-cal approach to th e limiting resistance is simpler than the other possible approach.) In this this underdamped cas case e it is further assumed that the value of E c o at the time of of a

For an overvoltage no higher than 2E,, must be

restrike through the secondary arcing contacts is E , . (This assumes R to be small enough to cause no significant phase shift in the current after the resistor is inserted in the circuit.) For a restrike through the secondary arcing contact after a current pause of 180" following interrup tion of the resi resistor stor current, the pea peak k transient voltage voltage on th e capacitor wil willl be

the system short circuit capacity is at least one third or more of the circuit breaker rating, then for double restrikes, one finds overvoltages no greater than 2.0Em if I, is greater greater tha than n

voltage transient) = E c (peak voltage I Rn

E,

r

0.441Jc L

0.665&

(EqB32)

Or in terms of cir circuit cuit constants and as assuming suming

voltage phase-to-phase voltage arc shunting resistance (circuit breaker rated short-circuit current)

E q B33)

For an overvoltage no higherJthan 2E,, must be

RZ

R 2

R

or one finds overvoltages no greater than 3.0Em if I , is greater than operating voltage phase-to-phase

(Eq B29)

Since L is related to the system short-circuit capacity at the circuit breaker, and C is related to the capacitive current, Eq B29 may be manipulated to show the following: If th e system short-circuit capacity c apacity is at least one third or more of the circuit breaker rating, then for a single restrike through the secondary contacts after a zero current pause of 180 , he overvoltage ratio will be less than 2.0 if R is greater than

(0.441) perating phase-to-phase volt voltage) age) $(capacitive current) X (circuit breaker rated short-circuit current at operating voltage) With Wi th a simil similar ar consideration fo r two restrikes through the secondary arcing contacts, each with 180 zero current pause, it may be found that the peak transient voltage on the capacitor will be

unit arc shunting resistance resistance (circuit breaker rated short-circuit current)

B4. Transmission Line Line Switching ouble ouble Restrike Through Resistor I t is desirable to establish the minimum values of R for transient voltages of two times and three times normal voltage for specified conditions of restriking. Consider the equivalent circuit show n in Fig B 5 .   Then at the first restrike, Em +e, i f = R + Zo

E, (peak voltage voltage transient ) =

-

E,+2E,

1

+exp

( -$)1exp

(-&)

ib

eb = - 2 V , = -eo

(Eq B30) For mustan be overvoltage no higher than 3E,,

=-if

R

(Eq B37)

ib

+ e,, + e f (Eq B38)

In the general case, V, = - e ,

+ 2 E, + e o ) R +0Z o

(Eq B39)

R

2

/L

0.309J-c-

A t the instant of restrike e ,

(EqB31)

opposite polarity. Thus

= E,

with

50

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

.AC HIGH-VOLTAGE HIGH-VOLTAGE CIRCUIT B REA KER S RATED ON A SYMMETRICAL CURRENT BASIS

ANSI/IEEE C37.012-1979

if

Em Normal Line-to-Neutral Peak Voltage

Voltage at Time of Restrike eo Instantane ous Line Voltage ef, if For ward Traveling Wave Wavess

e b , ib Backward Traveling Waves

Z o Surge Impedance Resistance e R Pole Arc Shunting Resistanc V Ll Voltage after First Restrike V L2 Voltage after Second Restrike

Fig B5

I t has been assumed assumed t hat th e circuit breaker cleared at the first natural frequency current zero. Then e , = VL, just prior to the second restrike and i/ L2=

-

VLI + 2(Em

+

VU 1

m

Eq B41)

Substituting and solvin solving g for t he voltage voltage ratio ,

Solving for R , where 2 = 450 for the two voltage ratio cases of 3.0 and 2 .0, respectively respectively

(1)

2 110

for double restrikes restrikes and le less ss than three times normal voltage

( 2 ) R 2. 210

for double restrikes and les lesss than two times normal vo1 age

51

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

C37.43-1969 R 1974) Specifications for Distribution Fuse Links for Use in Distribution Enclosed, Open, and Open-Link Cutouts (ANSI)

C37.63-1969 R 1974) Requirements for Automatic Line Sectionalizers for Alternating-Current Systems, (includes supplement C37.63a-1973) (ANSI)

C37.44-1969 R 1974) Specifications for Distribution Oi Oill Cutouts and Fuse Links (ANSI)

C37.66-1969 (R 19 74 ) Requi C37.66-1969 Requirements rements for Oil-Filled Oil-Filled Capacitor Switches for Alternating-Current Systems (ANSI)

C37.45-1969 ( R 1974) Specifications for Distribution Enclosed Single-P ole Air Switche s (ANSI) C37.46-1969 ( R 19 74 ) Specifications for Power Fuses and Fuse Disconn Disconnecting ecting Switches (ANSI) C37.47-1969 R 1974) Specifications for Distribution Fuse Disconnecting Switches, Fuse Supports, and Current-Limiting Fuses (ANSI) C37.48-1969 R 1974) Guide for Application, Operation, and Maintenance of Distribution Cutouts and Fuse Links, Secondary Fuses, Distribution Enclosed Single-Pole Air Switches, Pow er Fuses, Fuse Disconnecting Switches, and Accesso Accessories ries (ANSI)

C37.85-1972 (R 978 ) Saf Safety ety Requireme Requirements nts for XRadiati on Limits for AC High-Voltage Power Vacuum Interrupters Used in Power Switchgear (includes supplement C37.85a-1972) (ANSI) C37.90-1978 Relays and Relay Systems Associated with Electric Power Apparatus ( ANSI/IEEE) C37.90a-1974 (R 19 79 ) G Guide uide for Surge Withstan Withstand d Ca Ca-pability (SWC) Tests (Supp lement t o ANSI/IEEE C37.90-1978) (ANSI/IEEE) C37.91-1972 R 19 79 ) Guide for Protective Rel Relay ay Applications to Power Transformers (ANSI/IEEE)

C37.48a-1980 Trial-Use Standard Application of Fuses in Enclosures (Revision of Section 8 , ANSI C37.471969) (ANSI (ANSI/IEEE) /IEEE)

C37.93-1976 Guide for Protective Relay Applications of Audio Tones over Telephone Channels (ANSI/ IEEE)

C37.50-1973 Test Procedures for Low-Voltage AC Power Circuit Breakers Used in Enclosures, (includes supplements C37.50a-1975 and C57.50b-1975) (ANSI) C37.51-1979 Conformance Testing of Metal-Enclosed Low-Voltage AC Power Circuit Breaker Switchgear Assemblies (ANSI)

C37.95-1974 R 1979) Guide for Protective Relaying of Utility-Co Utility-Consumer nsumer Interconnections Interconnections (ANSI/IEEE)

C37.52-1974 Test Pro cedure s for Low-Voltage AC Power Circuit Protectors Used in Enclosures (ANSI) C37.60-1974 Requirements for Automatic Circuit Reclosers for Alternating Current Systems (ANSI/ IEEE) C37.61-1973 Guide for the Application, Operation, and Maintenance of Automatic Circuit Reclosers (ANSI/IEEE)

C37.96-1975 Guide for AC Motor Protection (supersedes C37.92-1972 and C37.94-1972) (ANSI/IEEE) C37.97-1979 C37.97 -1979 Guide for Protective Rela Relay y Applications t o Power System B Buse usess (ANSI/IEE E) C37.98-1978 Standard for Seismic Testing of Relays C37.98-1978 (This standard complements ANSI/IEEE 344-1975) (ANSI/IEEE) C37.99-1980 Guide for the Protection of Shunt Capacitor Banks (ANSI/IEEE) C37.100-1972 Definitions for Power Swit Switchgear chgear (ANSI) (Includes definitions from C37.03-1964)

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

Authorized licensed use limited to: University of Massachusetts Boston. Downloaded on January 08,2015 at 10:15:07 UTC from IEEE Xplore. Restrictions apply.  

Related Standards Standards in the C37 Series C37.04-1979 Rating Structure foir AC High-Voltage Circuit Breakers Breakers Rated on a Symmetrical Curre nt Basis Basis (Consolidated edition, Including supplements C37.0 C37.04a, 4a, C37.04b, and C37.04c), (ANSI/IEEE) C37.06-1979 for Preferred Ratings and Related Capabilities AC High-Voltage Circuit Required Breakers Rated on a Symmetrical Current Basis (Consolidated edition, ANSI) C37.09-1979 Test Procedure for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis Bas is (Consolidated (Consolidated edition, ANS I/IEEE )

C37.17-1979 Tri p Devic Devices es for AC and General Purpose DC Low-Voltage Low-Voltage Power Circuit Breaker Breakerss ( ANS I) C37.18-1979 Standard Field Discharge Circuit Breakers Used in Enclosures for Rotating Electric Machinery ( ANSI/IEEE) C37.20-1974 Switchgear Assemblies, Including MetalEnclosed Enclo sed Bus (includes supplem ent C37.20a-1970, C37.20b-1972, C37.20~-1974,C37.20d-1978) C37.20~-1974, C37.20d-1978) (Consolidated edition, ANSI/IEEE) C37.23-1970 ( R 19 77 ) Gu Guide ide f or Calcu Calculati lating ng Losses Losses in Isolated-Phase Bus (ANSI/IEE E)

C37.010-1979 Application Guide for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis (Consolidated edition, ANSI/IEEE)

C37.24-1971 ( R 197 6) Guide for Eva Evalua luati ting ng t he E ffect of Solar Rad iation on O utdoo r Metal Metal-Cla -Clad d Switchg Switchgear ear ( ANSI/IEEE)

C37.011-1979 Application Guide for Transient Recovery Voltage for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis (Consolidated edition, ANSI/IEEE) (Revision of C37.0721-1971)

C37.26-1972 ( R 19 77 ) Guid Guide e for Method Methodss of Power Factor Measurement for Low-Voltage Inductive Test Circuits (ANSI/IEEE)

C37 O12-1979 Application Guide for Capacitance Current Switching of AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis, (Consolidated edition) (ANSI/ IEEE) (Revi (Revision sion of C37. C37.07 07 31 1 73) C37.1-1979 C37.1-197 9 Standard Definition, Specification and Analysis of Manual, Automatic, and Supervisory Station Control and Data Acquisition (ANSI/IEEE) C37.2-1979 Sta ndar d Electrical Power Sys tem Device Device Function Numbers (ANSI/IEEE) C37.4-1953 ( R 1976) Definitions and Rating Structure for AC High-Voltage Circuit Breakers Rated on a Total Current Basis [includes supplements C37.4a195 8 (R 19 66) and C37.4bC37.4b-197 1970 0 (R 19 71) ((reaffir reaffirmed med wit with h change change in title)] (ANSI) and C37. 4~- 198 0 ANSI/ IEEE) C37.5-1979 Guide for Calculation of Fault Currents for Application of AC High-Voltage Circuit Breakers Rated o n a Total Current Basi Basiss (ANSI/IEEE) C37.6-1971 R 1976) Schedules of Preferred Ratings for AC HighHigh-Volt Voltage age Circuit Breakers Breakers Rate d on a Total Current Basis Basis (ANSI ) C37.7-1960 R 19 76 ) Factors (reaffirmed chang change e in title) Interrupting Rating for with Reclosing Service for AC HighHigh-Volt Voltage age Circuit Breakers Breakers Rated on a Tota l Current Basis (ANSI) C37.9-1953 ( R 19 76 ) (reaffi (reaffirmed rmed with chan change ge in title) Test Code for AC High-Voltage Circuit Breakers Rated on a Total Current Basis [includes supplement C37.9a1970 R 1971)] (ANSI) C37.11-1975 Requirements for Electrical Control for AC High Volt Voltage age Cir cuit Breakers Rat ed on a Symmetrical Current Basis and a Total Current Basis (ANSI) C37.12-1969 (R 19 74 ) Guide Specifications for A AC C High-Vol High -Voltage tage Circuit Breakers Ra ted on a Symmetrical Current Bas Basis is and a Tota l Curren t Bas Basis is (ANSI) C37.13-1980 Low-Voltage AC Power Circui t Breakers Used in Enclosures (ANSI/IEEE) C37.14-1979 Low-Voltage DC Power Circuit Breakers Used Use d in Enclosures (ANSI/IEE E)

C37.27-1972 Applica tion Guide for Low-Voltage A AC C Non-Integrally Fused Power Circuit Breakers (Using Separately Mounted Current-Limiting Fuses) (ANSI/ IEEE) C37.29-1974 Stan dard for Low-Voltage AC Power Circuit Protectors Used in Enclosures ( ANSI/IEEE) C37.30-1971 Definitions and Reauirements for HiehVoltage Air Switches, Insulators-, and Bus Supports (ANSI/IEEE) C37.30a-1975 Supplem ent to C37.30- 1971, (ANSI/ C37.30a-1975 IEEE) (sold separately) C37.3Og-1 C37.3O g-1980 980 D efinitions and Requirem ents f or HighVotlage Air (partial revision of ANSI/IEEE C37.301971 ) (ANSI/IEEE) C37.31-1962 ( R 1969) Electrical and Mechanical Characteristics of Indoor Apparatus Insula Insulators tors (ANSI) C37.32-1972 Schedules of Preferre d Ratings , Manufacturing Specifications, and Application Guide for High-Voltage Air Switches, Bus Supports, and Switch Accessories (ANSI) C37.33-1970 ( R 19 76 ) Rated Control Vol Voltag tages es and their Ranges for High-Voltage Air Switches (ANSI) C37.34-1971 ( R 19 77 ) Test Code for High High-Volt -Voltage age Air Air Switches (ANSI/IEEE) C37.34a-1975 C37.34a -1975 separately

su pplement

to

C37.34-1971,

sold

C37.35-1976 Guide for the Application, Installatio n, C37.35-1976 Operation, and Maintenance of High-Voltage Air Disconnecting and Load Interrupter Swit Switche chess (ANS I) C37.37-1979 Loading Guide for AC High-Voltage Air Switches (I n Ex Excess cess of 1 00 0 Volts) (rev (revisio ision n of C37.37197 1) (ANSI/IEEE) C37.40-1969 R 1974) Service Conditions and Definitions fo r Distribution Cutouts and Fuse L inks, Secondary Fuses, Distribution Enclosed Single-Pole Air Switches, Power Fuses, Fuse Disconnecting Switches, and Accessories Accessories (ANSI) C37.41-1969

Design ign Tests for Distribution R 19 74 ) Des

Cutouts and Fuse Links, Secondary Fuses, Distribution Enclosed Single-Pole Air Switches, Power Fuses,