Toshiba GR200 Series Instruction Manual page 314

Circuit breaker fail protection (CBF)
When a circuit breaker (CB) fails to remove a fault as a consequence of the CB failing to open,
the function of circuit breaker fail protection (CBF) is to remove the fault by the back-tripping
of other CBs. For example, if a fault current continues to flow following the issue of a trip
signal, the CBF function determines that a CB failure has occurred and issues another trip
signal to the adjacent CB(s) and/or the upstream CB.
Although a trip signal will have been issued by other protection functions, CBF protection
has relay elements and timers that are used to detect the continuing presence of a fault
following the issuance of a trip signal. The relay elements are termed OCCBF† and EFCBF†,
which run as protection functions within CBF.
†Note: The CBF function consists of two stages and their stages are operated
independently. Thus, the settings/switches/logics for two stages are provided
separately. To simply the description, only settings/switches/logics for the stage 1
are discussed as a representative, but the ones for the stage 2 are applicable in the
CBF function; hence the user can read the expression for the stage 1 as for the
stage 2 unless a special explanation or instructions has been provided.
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Note: Several IED models do not have circuit breaker failure protection features. To
determine whether the features are implemented in the IED or not, locate the IED ordering
number; and check the order number at "G&T position" referring to the comparison table below.
For more information, see
Table 2.20-1 Comparative table in respective ordering numbers
Circuit breaker failure protection
CBF
✓: Applicable
Appendix: Ordering
feature
NA: Not applicable
- 291 -
.
6F2S1914 (0.49)
Ordering No. at "G&T"
33 37
✓
✓
GRL200 (Soft 033 & 037)