Toshiba GR200 Series Instruction Manual page 67

Detecting the failure of circuit breakers
2.2.1
If current continues to flow for a pre-determined duration following the issuance of a trip
command, the CBF function will determine that a CB failure has occurred. The existence of
the current is detected by an overcurrent element (OCCBF_CH*) provided in each phase of the
primary circuit of the CT. The user can set the detection level of the relay element using the
settings [OCCBF_CH1] to [OCCBF_CH24].
The OCCBF_CH* relay characteristic is a circle that has a center at the origin, as shown
in Figure 2.2-1. The circle shows the threshold value of the OCCBF_CH* element, which is set
with [OCCBF_CH*]; the hatched area shows the operational area.
Figure 2.2-1 Characteristic of OCCBF_CH* element
The OCCBF_CH* element monitors the current in the CH*; if the current is above the
threshold value, the OCCBF_CH* element is activated. If the current falls below 80% of the
threshold value, the OCCBF_CH* element is reset.
Setting items Mode / range
OCCBF-CH
Protection scheme
2.2.2
Three protection schemes are available in CBF; the CBF function uses the arrangements
provided by these schemes to remove the fault from the power system. Three schemes are
provided:
1) Re-trip scheme: the CBF issues a further trip command to the target CB that has
2) Zone-trip scheme: the CBF issues trip commands to all adjacent CBs within the
3) Transfer-trip scheme: the CBF issues a transfer-trip command to trip the CB at the
0
Table 2.2-2 CBF OC relay setting
Unit
0.10 – 5.00 –
failed.
protection-zone.
remote-terminal.
- 53 -
OCCBF_CH*
I in CH*
Operation
Contents
Multiplier setting. The multiplier will set
OC relay threshold. Setting coefficient
can be calculated
percentage ratio of CT secondary rating
6F2S1931 (0.20)
Default
1.00
based on the
Centralized GRB200
(Soft: 030, 031, 032, 033, 034)