This document discusses breaker failure protection schemes. It notes that the last major publication on the topic was in 1982, so the PSRC K2 working group was established to investigate updated practices. The group has over 60 members and will prepare a guide covering modern breaker failure protection applications. The summary discusses key components of breaker failure schemes including current detectors, timing requirements, and considerations for different system configurations. It concludes with recommendations for ensuring schemes operate only when needed and provide adequate clearing times.

1. Breaker Failure Protection
PSRC – K2 WG

2. Last Publication on Breaker
Failure Protection by PSRC
 An IEEE PSRC Report , “Summary
Update of Practices on Breaker Failure
Protection”, IEEE Transaction Power
Apparatus and Systems, Vol. PAS-101,
No. 3, pp 555-563 , March 1982

3. Why a Guide ?
 Things have changed in 20 years.
 New Engineers need guidance.
 Breaker Failure Function being
incorporated in multifunction relays.

4. PSRC – K2
 Established 2001
 60 Working Group members

5. K2 Members
 Roger Hedding, Chair
 S.Anderson
 Alex Apostlov
 John Appleyard
 Roy Ball
 George Bartok
 Ron Beazer
 Ken Behrendt
 Robert Beresh
 Martin Best
 Gustav Brunello
 Art Buanno
 Zeeky Bukhala
 Arvind Chaudhary, Vice Chair
 Simon Chano
 Terry Crawley
 Randy Crellin
 Randy Cunico
 Albert N. Darlington
 Paul Drum
 Walt Elmore
 David Emigh
 Jon Ferraro
 Kelly Gardner
 Tony Giuliante
 George Gresko

6. K2 Members
 Irwin Hassenwinkle
 Stan Horowitz
 Randy Horton
 Mohamed Ibrahim
 Bob Jackson
 Gerald Johnson
 Peter Kemp
 Tim Kern
 Shoukat Khan
 Mike Kloiber
 Gary Kobet
 Tom Lanigan
 Larry Lawhead
 Bill Lowe
 Vahid Madani
 Walter McCannon
 Mike McDonald
 Dean Miller
 Pratap Mysore
 Mukesh Nagpal
 George Nail
 Russell Patterson
 Frank Plumptre
 Elmo Price
 Dan Reckerd
 Don Sevcik
 Charles Sufana
 Joe Uchiyama
 Sahib Usman
 Don Ware
 James Whatley
 Roger Whittaker
 Skip Williams
 Ray Young
 Rich Young

7. Assignment
 This working group will investigate issues
pertaining to breaker failure protection which
will include : breaker failure mechanisms,
fault detectors, breaker failure circuits, effect
of bus configurations, effect of multifunction
microprocessor relays, and the effect of
modern breaker control schemes. Prepare a
guide covering the application of
breaker failure protection to power
circuit breakers.

8. Why Breaker Failure Protection
?
Figure 1 - Remote Breaker Clearing
A
B C
LOAD LOAD
LOAD
FAULT
8
6
4
3
5
7
2
1

9. Basic Breaker Failure Scheme
AND Timer
50BF
BFI
Breaker Failure
Scheme Output
62-1

10. Timing Chart
TOTAL FAULT CLEARING TIME
FAULT CLEARED
FAULT OCCURS
TIME
62-1 BREAKER FAILURE TIMER TIME
AUX
TRIP
RELAY
TIME
BREAKER
INTERRUPT TIME
50BF
CURRENT
DETECTOR
RESET TIME
MARGIN
TIME
PROTECTIVE
RELAY
TIME
BFI
REMOTE BACKUP BREAKER
INTERRUPT TIME
TRANSFER TRIP
TIME
LOCAL BACKUP BREAKER
INTERRUPT TIME

11. Two Components
 Current Detector
 Breaker Failure Timer

12. Current Detector
 Detects current flow
 Pick up for minimum fault
 If phase current set above load current
 If ground current set above unbalance
 Drop out not delayed by dc offset
 Use 52a only if no current

13. Timer
 Longer than it takes the breaker to
clear a fault
 Shorter than the Critical Clearing Time
plus some margin.
 Could be longer for Line to Ground
Faults than for Three Phase Faults

14. Critical clearing Time
 Dictated by Transient Stability limit
 Somewhere between 7 and 30 cycles
 Results from Stability Study

15. Total Clearing Time
The sum of :
BFI pick up + Breaker Failure Timer +
Auxiliary trip relay time + Local back up
breaker time + (Transfer trip time if
remote)

16. Transient Stability time
 Severity of Fault
 Loading on System
 Mass of Generators
 Type of Fault

17. Circuit Breaker Failure Modes
 Failure to Trip
 Failure to Clear

18. Failure to Trip
 Contacts do not open after trip circuit
energized.
 Short or open in Trip coil
 Mechanical problem with breaker

19. Failure to Clear
 Contacts open but fault not
extinguished.
 Current continues to flow
 Mechanical or Dielectric problem
 Why auxiliary switches not reliable

20. Breaker Failure ReTrip
AND
Timer
Timer
BFI
50BF
62-1
Breaker Failure
Scheme Output
Re-Trip the
Breaker
(Time Delay May be Zero Time)
62-2

21. Elimination of 50BF Reset Time
AND
Timer
50BF
BFI
62-1
Enables 50BF
Breaker Failure
Scheme Output

22. Addition of Control Timer
AND
Timer
50BF
BFI
Breaker Failure
Scheme Output
62-1
Enable
Control
timer
Enabled only after
62-1 times out

23. Breaker Failure Seal-In
AND
50BF
BFI
OR
Timer
62-1
Breaker Failure
Scheme Output

24. Minimum Fault Current
 Use where current magnitude may not
be enough to pick up current detector
 Transformers
 Generators
 Harmonic Filters

25. Minimum Fault Current
52a
50BF
BFI
AND
OR
Timer
62-1
Breaker Failure
Scheme Output

26. Ring Bus Application
Ring Bus
21/
79
21/
79

27. Ring Bus
 Separate Ct inputs into relay
 Careful of current distribution after one
breaker opens in setting current
detectors.
 Another Working group (K5) to look into
this issue.

28. Distributed Breaker Failure
GOOSE
Fault Point
Breaker Failure
Protection
Relay Relay Relay
Trip

29. Design Considerations
 Total Breaker Failure clearing time
should be less than system stability
limit.
 Independent of type of failure detected
 Should operate during loss of dc to
breaker

30. Conclusions
 BFP should operate only when desired
 Timer setting should allow adequate margin
between backup breaker clearing and system
critical clearing time.
 Multiple timers can be used for different types
of faults
 Use auxiliary contacts as last resort for BFI.

31. Conclusions
 Phase current detectors should be set above
load to protect from scheme operating during
testing.
 Seal in circuits should be used to insure
breaker failure scheme does not drop out
prematurely
 Care should be taken when applying breaker
failure to ring bus and breaker and one half .

32. Questions ?