Summary of Relay Trip Circuit Design

Relay Trip Circuit Design Special Publication of the IEEE PSRC Written by a WG of the Substation

Equipment Protection Subcommittee Summary Paper in the conference

Proceedings Full document available for downloading

from the PSRC web site URL is given in the Summary Paper

Purpose Document and share information about

electric utility practice in the design of– relay trip circuits– associated control and protective functions

Provide training and reference information for new relay engineers

Subject Areas Substation Dc Systems

Relays Tripping a Single Breaker

Relays Tripping more than one Breaker

Breaker Failure Relaying Initiation

Transfer Tripping

Subject Areas, cont. Pole Disagreement Tripping Trip Circuit Monitoring and Supervision Reclosing Initiation and Cancellation Trip Circuit Apparatus Bibliography and References Appendix: Target Test Results

Substation DC Systems

DC systems overview– one feeder per breaker vs. tapped feeders– relay feeders– redundancy

Feeder per Breaker Dc System

PR

PR

PR+ A U X

+ A UX

+ A UX

A + : CB A UX ILIA RY POW ERCB: CIRCUIT BREAK ERA UX: RELAY AU XILIARY PW R.PR: PROTECTIVE RELAY

TRIP CON TACTTC: CB TR IP COIL52a: CB A UX ILIA RY SW ITCH

LINE 1 LINE 2 LIN E 3 CB1 CB 2 CB 3

52a 52a 52aTC TC TCA + A + A +

Feeder-per-CB with Relay Feeder

Other PR’s

+AUX-

94PR

94PR

52a 52aTC TC

A+ : CB AUXILIARY POWERCB: CIRCUIT BREAKERAUX: RELAY AUXILIARY POWER

PR: PROTECTIVE RELAYTRIP CONTACT

TC: CB TRIP COIL

52a: CB AUXILIARY SWITCH94/PR: PROTECTIVE/AUXILIARY

TRIPPING RELAY

LINE 1 LINE 1 CB1 CB2

A+ A+

Substation DC Systems

Trip circuit routing– radial versus loop dc

DC fault currents and coordination

Radial Dc

PR PR PR

52aTC

52aTC

52aTCA+ A+ A+

A+: CB AUXILIARY POWERCB: CIRCUIT BREAKER.PR: PROTECTIVE RELAY

TRIP CONTACTTC: CB TRIP COIL52a: CB AUXILIARY SWITCH

LINE 1 LINE 2 LINE 3 CB1 CB 2 CB 3

NOTE: DC PROTECTIVE DEVICES (FUSE OR CB’S) NOT SHOWN

Loop Dc

PR PR PR

52a 52a 52aTC TC TC

A+A+ A+

A+: CB AUXILIARY POWERCB: CIRCUIT BREAKER.PR: PROTECTIVE RELAY

TRIP CONTACTTC: CB TRIP COIL52a: CB AUXILIARY SWITCH

LINE 1 LINE 2 LINE 3 CB1 CB 2 CB 3

NOTE: DC PROTECTIVE DEVICES (FUSE OR CB’S) NOT SHOWN

Single Breaker Tripping Direct Trip

Indirect Trip– Diodes– Auxiliary relays

Dual breaker trip coils

Direct Trip - Single Breaker

52b

52a

TC-1

01 T SI PR-1 PR-2 RG

(+ )

( - )

TSI

Dual Trip Coils - Single CB

G

52b

01 T

86BF R 62Y SR-1R86

BF 62XPR-1

52a

TC-1 52a 62X TC-2

52a

62Y

Multiple Breaker Tripping Diodes versus Auxiliary Relays

Application of Diodes in Control Circuits

Application of Auxiliary Relays

Targeting with Auxiliary Relays

Trip Testing and Trip Test Switches

Trip two CB’s with Diodes

52a

TTSTTS

RDS

01 T

01 TR R

SI

SIPR

BREAKER 52-2 (+ )SWITCHBOARD (+ )

BREAKER 52-2 (-) BREAKER 52-1 (-)

TC TC

BREAKER 52-1 (+ )

52a

Trip two CB’s with Aux. RelaySWITCHBOARD (+ )

BREAKER 52-2 (+ ) BREAKER 52-1 (+ )

52-2 a

BREAKER 52-2 (-) BREAKER 52-1 (-)SWITCHBOARD (-)

01 T

01 T

SI

SI

RDSTTS TTS

94

94

52-2 a

52-1 a

52-1 a

R R

TC TC

PR94

Breaker Failure Relay Initiation Separation of Relay Circuits and Breaker

Trip Circuits

Maintaining Breaker Failure Initiation

BFI Auxiliary Relays

Breaker Auxiliary Switches

Transfer Tripping Transmitter Keying

Receiver Output Circuits

Direct Transfer Tripping

Permissive Overreach Transfer Tripping

52b Switch Keying

Pole Disagreement Tripping Independent pole tripping

Disagreement detection

Redundant dc supplies

Pole Disagreement Tripping

Trip Circuit Monitoring Trip circuit failure areas

Red light monitoring

Monitoring relays

Auxiliary relay circuit monitoring

Sneak circuits caused by monitoring

Red Light Trip Circuit Monitor

52a52b

R94G

TRIPCOIL

Reclose Initiation and Cancellation

Function of RI and RC signals

Means of deriving RI and RC from trips

Pulse duration considerations

Reclose Initiation - Shunt

79X

Reclose Initiation - Series

Trip Circuit Apparatus

Characteristics of trip circuit devices– Auxiliary Relays– Target and Seal-in Devices– Breaker Trip Coils

Coil Current Interruption

CONTACT WITHSTANDSVs MAX

CONTACTSBREAK DOWN

VOLTAGEACROSS COIL

TIME

CONTACTBREAKDOWN VOLTAGE

0

(+ ) VDC

Trip Circuit Apparatus, cont.

Surge protection devices– avoiding false trips caused by dc grounds and

surge suppression capacitors– coil surge suppression devices

Inadvertant Dc Ground Tripping

3.2 k

3.2 k

GROUND LIGHT18 V

GROUND LIGHT18 V

Cp100 µFTYPICAL

Cn100 µFTYPICAL

65 v

65 v

(+ )

( )

F5

F1

F4

F2 F3

PROTECTIVERELAYS

TRIP BUS

52 a

52 a

52TC

52CC

AUXRELAY

Trip Circuit Apparatus, cont.

Switches in trip circuits– purposes– pro’s and con’s– trip testing

Summary Documents a large body of knowledge about

dc trip circuit design that is not available elsewhere

Useful in explaining the reasons behind practices to new engineers and in avoiding problems discovered by others

Pertains primarily to the pre-microprocessor era, but has useful lessons for the future