ABB RELION 650 SERIES, Technical Manual

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en05000132.vsd
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A1 B1
Feeder
Time axis
t=0 t=t
1
t=t
2
t=t
3
IEC05000132 V1 EN-US
Figure 430: Selectivity steps for a fault on feeder B1
where:
t=0
is The fault occurs
t=t
1
is Protection B1 trips
t=t
2
is Breaker at B1 opens
t=t
3
is Protection A1 resets
In the case protection B1 shall operate without any intentional delay
(instantaneous). When the fault occurs the protections start to detect the fault
current. After the time t
1
the protection B1 send a trip signal to the circuit breaker.
The protection A1 starts its delay timer at the same time, with some deviation in
time due to differences between the two protections. There is a possibility that A1
will start before the trip is sent to the B1 circuit breaker. At the time t
2
the circuit
breaker B1 has opened its primary contacts and thus the fault current is interrupted.
The breaker time (t2 - t1) can differ between different faults. The maximum
opening time can be given from manuals and test protocols. Still at t
2
the timer of
protection A1 is active. At time t
3
the protection A1 is reset, that is the timer is
stopped.
In most applications it is required that the times shall reset as fast as possible when
the current fed to the protection drops below the set current level, the reset time
shall be minimized. In some applications it is however beneficial to have some type
of delayed reset time of the overcurrent function. This can be the case in the
following applications:
1MRK 506 382-UEN A
Section 23
Inverse time characteristics
Line distance protection REL650 2.2 IEC 891
Technical manual