Technology and SolutionsProtection and Substation Automation

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Topic:

END FAULTPROTECTIONAPPLICATION

BASICS BASICS

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WTopic Objectives

r Definition Protection Zone - Physical Zone

r Definition End- Fault Conditionr Fault clearance without EFP

r Fault evaluation

r EFP applicationr Fault clearance with EFP

r End- Fault Condition in a bus- coupler

r CB auxiliary circuitsr Modern protection systems

r BBP - additional CB functionality on feedersr Future standards

Objectives

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1 CT

Definition Protection Zone - Physical Zone

2 CTs (overlapped protection zones)

busbar zone

(physical)

line zone

(physical)

protection zone

protection zone

protection zone

protection zone

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WDefinition End- Fault Condition

1 CT

2 CTs (overlapped protection zones)

End - Zone

End - Zone

End - Fault

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WBusbar Configurations

CT line side

CT bus side

CT overlapped

Selectivity

Speed

Selectivity

Speed

single or multiple busbar

1 1/2 breaker busbar

How will an End- Fault condition be cleared in different busbar

configurations (without any End-Fault Protection) ???

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Bus

bar

Fault clearance (without EFP)

I. Multiple BB, CT line side

G

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Line

G

Fault clearance (without EFP)

I. Multiple BB, CT line side

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Bus

bar

Line

G

Fault clearance (without EFP)

II. Multiple BB, CT bus side

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OC Back- up

Line

Dis

tanc

e

G

Fault clearance (without EFP)

II. Multiple BB, CT bus side

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EFP

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Bus

bar

Line

G

Fault clearance (without EFP)

III. Multiple BB, CT overlapped

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EFP

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G

Fault clearance (without EFP)

III. Multiple BB, CT overlapped

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EFP

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Line Distance

OC Back- up

OC Back- up

Fault clearance (without EFP)

IV. 1 1/2 CB BB, CT line side

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EFP

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OC Back- up

OC Back- up

Fault clearance (without EFP)

V. 1 1/2 CB BB, CT bus side

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EFP

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Fault clearance (without EFP)

VI. 1 1/2 CB BB, CT overlapped

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EFP

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CT line side

CT bus side

CT overlapped

single or multiple busbar

1 1/2 breaker busbar

Fault Evaluation

++ very good

+ acceptable

- critical

Selectivity

Selectivity

Speed

Speed

++

++++

++

++

+ -

---

-

-

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EFP

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Fault Evaluation

Conclusion:

An additional protection function is required in CT bus side and 1 1/2 circuit

breaker configuration without overlapped CTs

!!!

ð End- Fault Protection Function

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EFP

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logic depending on the switchgear configuration (CT bus side, Line side;

1 1/2 CB)

feeder current

End- Fault Protection Function

EFP

&

I >

remote tripping

intertripping

t = EFP pick up time (higher than the highest possible arc extinguish time + safety time

CB opent

~120 ms

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EFP

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Fault clearance (with EFP)

How will an End- Fault condition be cleared in

different busbar configurations (with End- Fault Protection)

???

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EFP

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Bus

bar

Line

G

Fault clearance (with EFP)

II. Multiple BB, CT bus side

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EFP

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G

Fault clearance (with EFP)

II. Multiple BB, CT bus side

EFP

Intertripping

ð Fault cleared selectively !!!(~250ms)

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EFP

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Fault clearance (with EFP)

IV. 1 1/2 CB BB, CT line side

EFPIntertripping

Remote trip

ð Fault cleared selectively !!!(~250ms)

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EFP

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Fault clearance (with EFP)

V. 1 1/2 CB BB, CT bus side

EFP

ð Fault cleared selectively !!!(~250ms)

Intertripping

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EFP

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How will an End- Fault condition be cleared in a bus- coupler (without any

EFP)

???

End- Fault Condition in a Bus- Coupler

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EFP

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BB1

BB2

End- Fault Condition in a Bus- Coupler

~ ~

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EFP

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End- Fault Condition in a Bus- Coupler

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EFP

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⇒ by the coupler function of the

BUSBAR protection

End- Fault Condition in a Bus- Coupler

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EFP

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r a bus- coupler

End Fault Protection application

r multiple BB configuration with CT bus sider 1 1/2 circuit breaker configuration without

overlapped CTs

Summery:An EFP function in strictly required in:

It is not required in:r configuration with overlapped CTs

It will reduce the tripping time in:r multiple BB configuration with CT line side

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EFP

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CB auxiliary circuits

What “problem” will occur in case on a “switch

onto fault” situation???

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EFP

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CB auxiliary circuits

CB open !!!

CB closing command

flash over before CB indicates closed

⇒ EFP will trip the BB wrongly

EFP enabled

I>

CT bus side

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CB auxiliary circuits

CB open !!!

CB closing command

flash over before CB indicates closed

⇒ EFP will trip the line remote end wrongly

EFP enabled

I>

CT line side

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EFP

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⇒ in case on a “switch onto fault situation” the EFP will generate a tripping signal before the closed indication appears

(flash- over in the circuit breaker)

CB auxiliary circuits

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EFP

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CB auxiliary circuits

How can this be avoided???

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EFP

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⇒ the protection system must be informed in advance that the CB is going to be closed

⇒ by the (manual) close command of the CB

CB auxiliary circuits

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logic depending on the switchgear configuration (CT bus side, Line side;

1 1/2 CB)

feeder current

End- Fault Protection Function

EFP

&I >

remote tripping

intertripping

t = EFP pick up time (higher than the highest possible arc extinguish time + safety time

CB opent

~120 ms

CB (manual)

close command

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EFP

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Phase

R S T

CB / isolator auxiliary circuits

CB open

CB closed

++

protection

system

NC aux.

contacts

Phase

R

S

T

NC aux.

contacts

+

CB closing

coil

CB (manual)

close commandCB close

order

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