Ground Distance Protection

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Copyright © FPL and SEL 2015

Breaker Pole Scatter

and Its Effect on !adrilateral"ro!nd #istance Protection

James Ryan,Florida Power & Light Company 

 Arun Shrestha and Thanh-Xuan Nguyen,Schweitzer Engineering Laboratories, Inc.

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$!tline

• Breaker pole scatter 

• Zone 1 challenges hen protect!ng

short l!nes

• "uadr!lateral d!stance element

• #ase study

• Solut!on and test results

• #onclus!on

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Fa!lt Clearing %i&e

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'or&al Breaker Pole Scatter 

B# $ault current!nterrupt!on

Normal load current

!nterrupt!on

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(igh Breaker Pole Scatter 

%elayed &hase #current !nterrupt!on

'rare(

 AB $ault current

!nterrupt!on

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Factors )ffecting Breaker Pole Scatter 

• Breaker operat!ng mechan!sm

• %!electr!c strength o$ arc !nterrupters

•)*ternal c!rcu!t parameters dur!ng $ault

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Protection of Short Lines

• +ault res!stance can e s!gn!$!cantly h!gherthan l!ne !mpedance

• ho ground d!stance elements ha.e

l!m!ted $ault res!stance co.erage

• "uadr!lateral ground d!stance elements

are pre$erred

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Fa!lt on Short %rans&ission Line

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!adrilateral "ro!nd #istance Ele&ent

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Factors %hat *ay )ffect !adrilateral

"ro!nd #istance Ele&ent

• /pen-pole cond!t!ons

• Breaker pole scatter 

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Case St!dy

• Study e$$ect o$ B0 pole scatter on relay at B1

• Test cases 'B0(

♦ Normal $ault current !nterrupt!on

♦ nterrupt!on delayed y 234 cycles !n one pole

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'or&al Fa!lt Interr!ptionB!s +

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Interr!ption #elayed ,y 0-5 Cycles

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Interr!ption #elayed ,y 0-5 CyclesB!s +

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Interr!ption #elayed ,y 0-5 CyclesB!s .

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+one 1 B" /eactance and

/esistance Calc!lation

5hen +SB asserts, relay !ssues tr!p command to reakers

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FPL Syste&

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Sit!ation Leading to

nintended $peration

• 6!gh reaker pole scatter o$

234 cycles 'rare(

• Strong sources at oth ends'SR 7 132(

• 8ery short l!nes

• 9arge res!st!.e co.erage $or :uadr!lateralground d!stance elements

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FPL nintended $peration

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+one 1 B" /eactance and

/esistance Calc!lation

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Proposed Sol!tion

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C$*%/)#E Play,ack %est

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/%#S   %est /e&ote Fa!lt

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/%#S %est +one 1 Fa!lt

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Concl!sion

• 6!gh reaker pole scatter may occur asreakers ear and age

• Zone 0 element super.!s!on adds secur!ty

to :uadr!lateral d!stance elements dur!ngpole-scatter operat!ng cond!t!ons !thout

sacr!$!c!ng dependa!l!ty

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!estions3