ABB RELION 620 Series Technical Manual page 540

Section 5
Protection-related functions
534
t maximum opening time for the circuit breaker
cbopen
t maximum time for the breaker failure protection to detect the correct breaker function (the current
BFP_reset
criteria reset)
t safety margin
margin
It is often required that the total fault clearance time is less than the given critical time. This
time often depends on the ability to maintain transient stability in case of a fault close to
a power plant.
GUID-1A2C47ED-0DCF-4225-9294-2AEC97C14D5E V1 EN
Figure 255: Timeline of the breaker failure protection
Timer 3
This module is activated by the CB_FAULT signal. Once activated, the timer runs until the
set CB fault delay value has elapsed. The time characteristic is according to DT. When the
operation timer has reached the maximum time value CB fault delay, the CB_FAULT_AL
output is activated. After the set time, an alarm is given so that the circuit breaker can be
repaired. A typical value is 5 s.
Retrip logic
The retrip logic provides the TRRET output, which can be used to give a retrip signal for
the main circuit breaker. Timer 1 activates the retrip logic. The operation of the retrip logic
depends on the CB fail retrip mode setting.
1MAC504801-IB E
620 series ANSI
Technical Manual