ABB Relion 670 Series Technical Reference Manual page 463

1MRK505222-UUS C
7.8.1
7.8.2
Technical reference manual
Introduction
Breaker failure protection (CCRBRF) ensures fast back-up tripping of surrounding
breakers in case the own breaker fails to open. CCRBRF (50BF) can be current based,
contact based, or an adaptive combination of these two conditions.
Current check with extremely short reset time is used as check criterion to achieve high
security against inadvertent operation.
Contact check criteria can be used where the fault current through the breaker is small.
CCRBRF (50BF) can be single- or three-phase initiated to allow use with single pole
tripping applications. For the three-phase version of CCRBRF (50BF) the current
criteria can be set to operate only if two out of four for example, two phases or one
phase plus the residual current pickups. This gives a higher security to the back-up trip
command.
CCRBRF (50BF) function can be programmed to give a single- or three-phase re-trip
of the own breaker to avoid unnecessary tripping of surrounding breakers at an
incorrect initiation due to mistakes during testing.
Operation principle
Breaker failure protection CCRBRF (50BF) is initiated from protection trip command,
either from protection functions within the IED or from external protection devices.
The initiate signal can be phase selective or general (for all three phases). Phase
selective initiate signals enable single pole re-trip function. This means that a second
attempt to open the breaker is done. The re-trip attempt can be made after a set time
delay. For transmission lines single pole trip and autoreclosing is often used. The re-
trip function can be phase selective if it is initiated from phase selective line protection.
The re-trip function can be done with or without current check. With the current check
the re-trip is only performed if the current through the circuit breaker is larger than the
operate current level.
The initiate signal can be an internal or external protection trip signal. This signal will
initiate the back-up trip timer. If the opening of the breaker is successful this is
detected by the function, by detection of either low current through RMS evaluation
and a special adapted current algorithm or by open contact indication. The special
algorithm enables a very fast detection of successful breaker opening, that is, fast
resetting of the current measurement. If the current and/or contact detection has not
detected breaker opening before the back-up timer has run its time a back-up trip is
initiated.
Further the following possibilities are available:
Section 7
Current protection
457