fundamentals of bus protection handouts

8/12/2019 Fundamentals of Bus Protection Handouts

1/13

FUNDAMENTALSOFBUS

PROTECTION

KevinWright

SeniorProtectionEngineer

SacramentoMunicipalUtilityDistrict

WHAT

IS

A

BUS?

5

WHATISABUS?

Allconnectionsareatthesamevoltage.

6

WHATISABUS?

Allconnectionsareatthesamevoltage.

Madeofbusbarsuchasinswitchgearor,

overheadtransmissionlineconductorortube

suchas

in

open

air

substations.

7


2/13

WHAT

IS

A

BUS? Allconnectionsareatthesamevoltage.



suchasinopenairsubstations.

Node

8

WHAT

IS

A

BUS? Allconnectionsareatthesamevoltage.



suchasinopenairsubstations.

Node

ZeroImpedance

9

BUSCONFIGURATIONS

SingleBus/SingleBreaker

10 11


3/13

BUS

CONFIGURATIONS


BreakerandAHalf

12 13

BUSCONFIGURATIONS


BreakerandAHalf

DoubleBus/DoubleBreaker

14 15


4/13

BUS

CONFIGURATIONS


BreakerandAHalf


MainandTransfer

16 17

18

BUSCONFIGURATIONS


BreakerandAHalf


MainandTransfer

Ring

19


5/13

20

BUS

PROTECTION

CHALLENGES Varietyofconfigurations

21

BUSPROTECTIONCHALLENGES

Varietyofconfigurations

Lar e number of connections

22

BUSPROTECTIONCHALLENGES Varietyofconfigurations

Largenumberofconnections oranexterna au t,oneseto currenttrans ormers

(CTs)willseetotalcurrent

23


6/13

BUS

PROTECTION


Largenumberofconnections ,

willseetotalcurrent

24

BUS

PROTECTION


LargenumberofconnectionsForanexterna au t,oneseto currenttrans ormers

(CTs)willseetotalcurrent

HighavailablefaultcurrentCTsaturation

25

[1]26

CURRENTTRANSFORMEREQUIVALENTCIRCUIT

27


7/13

CURRENTTRANSFORMEREQUIVALENTCIRCUIT

28 29

TYPESOFBUSPROTECTION

Overcurrent

r p oc ng c emes

CommunicationBasedSchemes

HighImpedance

Current

Differential

LowImpedanceCurrentDifferential

LinearCoupler

ArcFlashDetection

30 31


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32 33

DIFFERENTIALPROTECTION

Currentdifferentialprotectionverifiesthatall

currentt at ows ntoap eceo equ pment

alsoflowsout.

34 35


9/13

DIFFERENTIAL

PROTECTION Currentdifferentialprotectionverifiesthatall


alsoflowsout.

HighImpedancebusdifferentialprotectioncan

accommodateanynumberofterminals.

Minimizessaturationeffect.

36 37

[2]

38 39


10/13

DIFFERENTIAL

PROTECTION Currentdifferentialprotectionverifiesthatall


alsoflowsout.

Lowimpedancebusdifferentialprotectioncan

accommodateavarietyofcurrenttransformer

ratios,buthasalimitednumberofcurrentinputs.

40 41

42

LINEARCOUPLER

VoltageDifferential

AirCoreMutualReactors

Couplersareconnectedinseries

Nosaturation

due

to

air

core

43


11/13

44

PROS

AND

CONSTYPE PROS CONSOvercurrent Simple

Inexpensive

Slow

Nothighlyselective

45

PROSANDCONSTYPE PROS CONS

Overcurrent Simple

Inexpensive

Slow

Nothighlyselective

TripBlockingSchemes Highspeed

Selective

Additional wiring

Dependence onotherrelays

46


Overcurrent Simple

Inexpensive

Slow

Nothighlyselective


Selective

Additional wiring


CommunicationBased

Schemes

Highspeed

Selective

Microprocessorbasedrelays

required

47


12/13


Overcurrent Simple

Inexpensive

Slow

Nothighlyselective


Selective

Additional wiring


CommunicationBased

Schemes

Highspeed

Selective


required

HighImpedanceDifferential Highspeed Selective

Easy toset

Easilyexpandable

DedicatedmatchedCTs

required

48


Overcurrent Simple

Inexpensive

Slow

Nothighlyselective


Selective

Additional wiring


CommunicationBased

Schemes

Highspeed

Selective


required


Easy toset

Easilyexpandable

DedicatedmatchedCTs

required

LowImpe ance

D erent a H g

spee

Se ect ve

Canuseshared

unmatched CTs

Flexible

L m te num ero

c rcu ts

49


Overcurrent Simple

Inexpensive

Slow

Nothighlyselective


Selective

Additional wiring


CommunicationBased

Schemes

Highspeed

Selective


required


Easy toset

Easilyexpandable

DedicatedmatchedCTs

required

owmpe ance eren a g spee e ec ve

Canuseshared

unmatched CTs

Flexible

m e num e ro c rcu s

LinearCoupler Highspeed Selective

Reliable

Expensive

Dedicatedcouplers

50


Overcurrent Simple

Inexpensive

Slow

Nothighlyselective


Selective

Additional wiring


CommunicationBased

Schemes

Highspeed

Selective


required


Easy toset

Easilyexpandable

DedicatedmatchedCTs

required

owmpe ance eren a g spee e ec ve

Canuseshared

unmatched CTs

Flexible

m e num e ro c rcu s

LinearCoupler Highspeed Selective

Reliable

Expensive

Dedicatedcouplers

ArcFlashDetection Highspeed Limitedapplication51


13/13

References[1] A. R. Leoni and J. E. Bowen, Improving Safety and Reliabil ity Via Cost-Effective Upgrades of

Existing Systems,IEEE Trans. Ind. Appl.,vol. 43, no. 1, pp. 130-138, Jan./Feb. 2007

[2] H. J. Li of Westinghouse, Applied Protective Relaying, 1979

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