Breaker Failure Protection

Breaker Failure Protection

Backup Protection
A B
1 2 3 Fault X 4

Local backup is the additional (or secondary, redundant) protection provided for the primary zone to assure breaker trip if the primary relaying fails. Remote backup is the overlapping of the primary zone provided by remote (adjacent busses) protection that will operate, after a suitable coordinating time, if the primary zone breaker does not trip. Relays at 1 protecting line AB are also remote backup to relays at 3 protecting line BC. Breaker failure is initiated when the primary and/or local backup relays have operated and the local breaker fails to trip.
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Breaker Failure Protection

Backup: Local, Remote and Breaker Failure

Remote Backup Relays

Remote Backup Relay Time Delay

Trip Remote Breaker

Breaker Failure Protection

Remote Backup
A B
1 2 3 Fault X 4

Fault on line BC - Failure of breaker 3 to operate Relays at 1,5 and 8 are backup to to relays at 3 Backup relays may not see fault due to infeed Coordination time may be undesirably slow Sequential remote tripping If one remote can see the fault and clear there will be a redistribution of fault currents reducing the effect of infeed The second remote relay will trip eliminating infeed The last remote relay will trip
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Breaker Failure Protection

Breaker Failure

EHV and UHV Applications Greater fault currents produce more stress on power circuit breakers Stability demands for faster backup clearing Critical Clearing Time

Thus, Local Breaker Failure Breaker failure does not preclude remote backup

Breaker Failure Protection

Breaker Failure and Remote Backup

4 3

Fault on line BC and relays at 1, 2 and 5 operate Breakers 1 and 5 trip - breaker 2 fails to operate Breaker failure at 2 trips breaker 3 and removes any infeed seen by relays at 4 Relays at 4 will operate as remote backup to clear fault Transfer tripping of breaker 4 by breaker failure at 2 is also possible Breaker Failure Protection

Breaker Failure Scheme

+ dc
Relay Scheme

+ dc 62X 50 62Y

#1

#2

52a

62X 52T 52a - dc

94

62Y 62 BF - dc

62BF 86 BF 86BF

Multiple

86BF
Contacts

- dc

50 - Phase and ground instantaneous overcurrent relays 52a - Breaker auxiliary contact, open when breaker is open 52T - Breaker trip coil 62X,Y - Breaker failure auxiliary (BFI) 62BF - Breaker failure timer 86BF - Breaker failure lockout relay 94 - Breaker trip relay (used for single trip coil applications)
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Breaker Failure Protection

Breaker Failure Logic

86BF

50 - Phase and ground instantaneous overcurrent relays 52a - Breaker auxiliary contact, open when breaker is open 62X,Y - Breaker failure auxiliary (BFI) 62BF - Breaker failure timer 86BF - Breaker failure lockout relay 86T - Transformer differential lockout
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Breaker Failure Protection

Single-line Single-breaker Bus

Typical Logic
62X,Y 50BF-1 62X,Y 50BF-2 62X,Y 50BF-3 62 BF 86 BF

N 50 BF

Line N Line Relays 62X,Y

62X,Y 50BF-N

Breaker Failure Protection

Breaker-and-a-half Bus

Line 1 Bus L 1 2

Line 2

4 3 50 3 Bus R

Breaker Failure 1 2 3

86 Relay Operations
Trip 2 and all Bus L breakers. Transfer trip Line 1 Trip 1 and 3. Transfer trip lines 1 & 2. Trip 2 and all Bus R breakers, such as 4. Transfer trip line 2

50 1

50 2 Line 2 Relays

Line 1 Relays

Breaker Failure Protection

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Ring Bus
Relays Line 1 Relays 4 50 4 50 3 3 86T Transformer Differential 1 50 1 2 Relays Line 3 50 2 Line 2
Breaker Failure 1 2 3 4 86 Relay Operations
Trip 2 and 4 Transfer trip lines 1 & 2 Trip 1 and 3 Transfer trip lines 2 & 3 Trip 2, 4, and 5 Transfer trip line 3 Trip 1, 3, and 5 Transfer trip line 1

Breaker Failure Protection

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Breaker Failure Logic

* 62X 62Y
50 52a Options 86T 52a T 0 62BF 86BF

62X,Y - Breaker failure auxiliary (BFI) Include both line relays 62X, Y for common breaker Breaker-and-a-half bus - center breaker Ring bus

Breaker Failure Protection

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Breaker Failure Time Chart

Relay Operate

Breaker Clearing 62X 62Y BFI

50 Reset

Margin 86 BF Local Backup Clearing TFR TRIP Remote Backup Clearing

62BF Timer Setting

Normal Clearing Local Backup BF Total Clearing Remote Backup BF Total Clearing

Breaker Failure Protection

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Breaker Failure

50BF Overcurrent Reset is affected by: Breaker arcing contacts and shunting resistors Fault current level prior to interruption CT saturation 50BF setting Breaker-and-a-half and ring bus applications Solid state relays have faster reset than electromechanical relays Reset is generally assured to be within one cycle using microprocessor relays -this is dependent on sampling and computation rate

Breaker Failure Protection

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Breaker Failure Logic

62X 62Y

50BF - Phase and ground torque controlled instantaneous overcurrent relays Relay cannot operate until after 62BF time Fast pickup, 0.25 to 1.0 cycle depending on setting and fault current Allows more sensitive setting Control timer resets breaker failure operation
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Breaker Failure Protection

Breaker Failure Time Chart

Relay Operate

Breaker Clearing 62X 62Y BFI

Margin 86 50 BF Pickup Local Backup Clearing TFR TRIP Remote Backup Clearing

62BF Timer Setting

Normal Clearing Local Backup BF Total Clearing Remote Backup BF Total Clearing

Control Timer T (Setting)

Breaker Failure Protection

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Critical Clearing Time

A maximum allowable time that a fault may persist before jeopardizing the integrity of the power system System location Loading Fault type Breaker failure clearing time including remote backup clearing must be less than critical clearing time

Breaker Failure Protection

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IPO Breakers

Independent Pole Operated Breakers Single pole tripping and reclosing Three pole tripping
On breaker failure
the opening of two phases on a three-phase fault will likely clear the fault or change the fault characteristic to single-phase-to-ground. Increase the maximum critical clearing time.

Pole Discrepancy detection becomes increasingly important

Breaker Failure Protection

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Pole Discrepancy

Based on auxiliary 52a and/or 52b contact positions Based on breaker current level

Breaker Failure Protection

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Pole Discrepancy

Auxiliary contact arrangement for three pole gang operated breaker position indication

Breaker Failure Protection

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Pole Discrepancy

Auxiliary contact arrangement for IPO breaker position indication Using 52a - parallel 52a = 0 (All poles open) 52a = 1 (Any pole closed) Using 52b - series 52b = 1 (All poles open) 52b = 0 (Any pole closed)

CIRCUIT BREAKER

A B C

A B C

52a 52a 52a Breaker Position

A 52b

B 52b

C 52b Breaker Position

Breaker Failure Protection

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Pole Discrepancy

Auxiliary contact arrangement for IPO breaker position indication Using 52a - series 52a = 0 (Any pole open) 52a = 1 (All poles closed) Using 52b - parallel 52b = 1 (Any pole open) 52b = 0 (All poles closed)

CIRCUIT BREAKER

A B C

A B C

52b 52b 52b Breaker Position

A 52a

B 52a

C 52a Breaker Position

Breaker Failure Protection

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Pole Discrepancy
CIRCUIT BREAKER

A B C

Auxiliary contact arrangement at IPO breaker Breaker position Pole discrepancy indication

A B C

52a 52a 52a Breaker position with 52a (any pole closed) Pole Discrepancy From Breaker

A B C

52b 52b 52b

Breaker Failure Protection

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Pole Discrepancy

Auxiliary contact arrangement at IPO breaker Breaker position with 52a and 52b Pole discrepancy logic in IED

Breaker Failure Protection

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Pole Discrepancy

CIRCUIT BREAKER

A B C

Auxiliary contact arrangement at IPO breaker Breaker position with 52a/pole Pole discrepancy logic in IED Particularly suitable for SPT

AND AND

A B C

52a - A 52a - B 52a - C

Pole Discrepency

IED Logic
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Breaker Failure Protection

Pole Discrepancy

Auxiliary contact arrangement at IPO breaker Breaker position with 52a and 52b per pole Pole discrepancy logic in IED Particularly suitable for SPT

Breaker Failure Protection

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Pole Discrepancy

Breaker Failure Protection

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Questions?

Breaker Failure Protection

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