Breaker Failure Protection

Breaker Failure Protection

Breaker Failure Protection

1

Backup Protection A

D







B 1

2

3

5

6

7

Fault X

4

8

C

E

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.

Breaker Failure Protection

2

Backup: Local, Remote and Breaker Failure Primary Relays Local Backup Relays 50BF

Remote Backup Relays

Breaker Failure Protection

Trip Local Breaker Breaker Failure Relay 62BF

Trip Local Adjacent Breakers

Remote Backup Relay Time Delay

Trip Remote Breaker

3

Remote Backup A

D

    

B 1

2

3

5

6

7

Fault X

4

8

C

E

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

Breaker Failure Protection

4

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

5

Breaker Failure and Remote Backup B 1 Fault X

5

C

2

A

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 

6

Breaker Failure Scheme + dc

+ dc

94

+ dc

Relay Scheme

Relay Scheme

#1

#2

62Y

62X 50

52a

52T - dc

      

94

62X 52a - dc

62BF

62Y 62 BF - dc

86 BF

Multiple

86BF Contacts

86BF

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)

Breaker Failure Protection

7

Breaker Failure Logic 62X 62Y 50

T

52a

0 86T

Options

     

86BF

62BF

52a

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

Breaker Failure Protection

8

Single-line Single-breaker Bus Bus Arrangement 1

Line 1

Typical Logic 62X,Y 50BF-1

2

Line 2

3

Line 3

62X,Y 50BF-3

N

Line N

62X,Y 50BF-N

50 BF

Breaker Failure Protection

62X,Y 50BF-2 62 BF

86 BF

Line Relays 62X,Y 9

Breaker-and-a-half Bus

Line 1

Line 2

4

Bus L 1

2

50 1

Breaker Failure Protection

3 50 3

50 2

Line 1 Relays

Breaker Failure 1

Bus R

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

Line 2 Relays

10

Ring Bus Relays Line 1

1

Relays

50 1

50 2 2

4 50 4

Line 2

50 3

Relays

3

Line 3

Breaker Failure 1 2 3 4

86T

5

Breaker Failure Protection

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

Transformer Differential

11

Breaker Failure Logic + dc

*

* 62X 62Y

62BF

50 52a

62Y

62X 50

62 BF - dc



86 BF 86BF

Options

T 0 86T 52a

86BF

62BF

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

Breaker Failure Protection

12

Breaker Failure Time Chart Normal Clearing Time Normal Clearing

Relay Operate

Failed Breaker

Breaker Clearing 62X 62Y BFI

50 Reset

Margin

62BF Timer Setting

86 BF

Local Backup Clearing TFR TRIP

Remote Backup Clearing

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

Breaker Failure Protection

13

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

14

Breaker Failure Logic Retrip

62X 62Y

T

T R

62BF Control Timer

    

0

50BF

86BF

Torque Control

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

Breaker Failure Protection

15

Breaker Failure Time Chart Normal Clearing Time Normal Clearing

Relay Operate

Failed Breaker

Breaker Clearing 62X 62Y BFI

Margin

62BF Timer Setting

86 50 BF Pickup

Local Backup Clearing Remote Backup Clearing

TFR TRIP Normal Clearing Local Backup BF Total Clearing Remote Backup BF Total Clearing

Control Timer T (Setting)

Breaker Failure Protection

R

16

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

17

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

18

Pole Discrepancy  

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

Breaker Failure Protection

19

Pole Discrepancy 

Breaker Failure Protection

Auxiliary contact arrangement for three pole gang operated breaker position indication

20

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

52a

B

52a

C

52a Breaker Position

A

B

C

52b

52b

52b Breaker Position

Breaker Failure Protection

21

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

52b

B

52b

C

52b Breaker Position

A

B

C

52a

52a

52a Breaker Position

Breaker Failure Protection

22

Pole Discrepancy CIRCUIT BREAKER



A B C

A

52a

B

52a

C

52a

A

52b

B

52b

C

52b

Breaker Failure Protection

Auxiliary contact arrangement at IPO breaker • Breaker position • Pole discrepancy indication

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

23

Pole Discrepancy 

Breaker Failure Protection

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

24

Pole Discrepancy 

CIRCUIT BREAKER

A

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

B C AND AND

A B C

Pole Discrepency

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

OR

IED Logic

Breaker Failure Protection

25

Pole Discrepancy 

Breaker Failure Protection

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

26

Pole Discrepancy

Breaker Failure Protection

27

Questions?

Breaker Failure Protection

28