ABB 615 series Technical Manual page 782

Section 5
Protection related functions
776
Timer 1
Once activated, the timer runs until the set Retrip time value has elapsed. The time
characteristic is according to DT. When the operation timer has reached the value set with
Retrip time, the retrip logic is activated. A typical setting is 0...50 ms.
Timer 2
Once activated, the timer runs until the set CB failure delay value has elapsed. The time
characteristic is according to DT. When the operation timer has reached the set maximum
time value CB failure delay, the backup trip logic is activated. The value of this setting is
made as low as possible at the same time as any unwanted operation is avoided. A typical
setting is 90 - 150 ms, which is also dependent on the retrip timer.
The minimum time delay for the CB failure delay can be estimated as:
CBfailuredelay Retriptime t
≥
A070693 V3 EN
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.
t t
+ + +
cbopen BFP reset _ margin
1MAC059074-MB A
(Equation 136)
615 series ANSI
Technical Manual