Toshiba GR200 Series Instruction Manual page 244

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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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The implementation of particular features is dependent upon the selection of

hardware and the configuration of functions. Several IED models do not support certain

features. To determine whether a particular feature has been implemented within an IED,

identify the IED ordering number; and check the order number for the "G&T position" whilst

referring to the comparison table below. For more information, see

Table 2.10-1 Comparative table in respective ordering numbers

✓: Applicable

Main features

NA: Not applicable

Ordering No. at "G&T"

6F2S1915 (0.46)

Appendix: Ordering

GRZ200 (Soft 031 & 032)