Toshiba GRE110 Instruction Manual page 46

Setting
The setting elements necessary for the breaker failure protection and their setting ranges are as
follows:
Element Range
CBF 0.10 – 10.0 A
TRTC 0.00 – 300.00 s
TBTC 0.00 – 300.00 s
[RTC] Off / DIR / OC
[BTC] Off / On
The overcurrent element CBF checks that the circuit breaker has opened and that the current has
disappeared. Therefore, since it is allowed to respond to load current, it can be set to 10 to 200% of
the rated current.
The settings of TRTC and TBTC are determined by the opening time of the original circuit breaker
(Tcb in Figure 2.8.2) and the reset time of the overcurrent element (Toc in Figure 2.8.2). The timer
setting example when using retrip can be obtained as follows.
Setting of TRTC = Breaker opening time + CBF reset time + Margin
= 40ms + 10ms + 20ms
= 70ms
Setting of TBTC = TRTC + Output relay operating time + Breaker opening time +
= 70ms + 10ms + 40ms + 10ms + 10ms
= 140ms
If retrip is not used, the setting of the TBTC can be the same as the setting of the TRTC.
The actual tripping time after BFP start will be added the time (approx. 15 to 20ms) consumed by
motion of binary input and output to above timer's settings. (Response time of binary inputs: less
than 8ms, Operating time of binary outputs: less than 10ms)
Step Default
0.05 A 0.50 A
0.01 s 0.50 s
0.01 s 1.00 s
Off
Off
CBF reset time + Margin
 45 
6 F 2 T 0 1 7 2
Remarks
Overcurrent setting
Retrip time setting
Back trip time setting
Retrip control
Back trip control