Iskra FPC 200 - Page 16

Functionality
16 USER MANUAL FPC 200 - 3/2017
Pickup drops when:
 Fault is not present anymore, the drop-out
delay runs out and the Trip signal has not set
yet or
 fault is not present anymore and Trip signal is
already set or
 a blocking occurs.
Pickup signal
Fault detection
Trip signal
Drop-out
delay
Pickup
delay
Pickup
delay
Trip
delay
Figure 2.4: Fault confirmation.
2.1.2.2 Trip logic
The Trip signal is intended for opening of circuit breaker,
which eliminates faulty element from power system.
Majority of faults have transient character and
disappear spontaneously. The duration of such faults is
relatively short. In order to avoid unnecessary opening
of circuit breaker the Trip signal can be delayed. Among
others the delaying of Trip signal may be used to ensure
selectivity along the power system network. The delay is
set with Trip delay parameter. In case the protection is
blocked the Trip signal will not set.
The Trip is set (Figure 2.5):
 When a fault is detected and
 when the pickup signal is stated and
 trip delay time runs out and
 no blocking is present.
Trip
Delay
&
Blocking
Pickup
Fault
detection
Trip
Figure 2.5: Trip set logic.
Trip signal drops:
 when the pickup drops or Blocking appears
When the protection trips there are some particular
delays on detection and trip execution levels. Several
milliseconds can pass during transfer of the signal to
external output relay and forward to the circuit breaker
switch of the circuit. The compensation of lost time is
solved with default value.
2.1.2.3 Blocking
Function is blocked when any pickup Block input is set. It can be set through digital input port or it can be set internally in
combination with different functions. When the protection is blocked the pickup signal drops and pickup blocked signal is
stated. Consequently after the pickup signal drops the Trip delay timer resets. After the blocking is reset and if the fault is
still present the protection function starts again. Protection operation with blocking signal turned on for a certain amount
of time is shown on Figure 2.6.
Pickup
Pickup block
Fault
Pickup blocked
Pickup
delay
Pickup
delay
Trip
delay
Trip
Trip
delay
Figure 2.6: Protection operation with blocking signal turned on for a certain duration.