P54x/EN CM/La4 Commissioning
(CM) 10-40
MiCOM P543, P544, P545 & P546
CM
For other differential settings or current injected into A phase (I
a
), the formula below can be
used (enter slopes in pu form, i.e. percentage/100):
2 Terminal & Dual Redundant:
Operate current is 0.5 x [(I
a
x k
2
) – {(k
2
– k
1
) x
s2
} +
s1
] pu +/- 20%
3 Terminal:
Operate current is 0.333 x [(1.5 x I
a
x k
2
) – {(k
2
– k
1
) x
s2
} +
s1
] pu +/- 20%
Ensure that I
a
> I
S2
Note: For 5 A applications the duration of current injections should be short
to avoid overheating of the variac or injection test set.
8.3.2 Current differential operation and contact assignment
8.3.2.1 Phase A
Retaini
ng the same test circuit as before, prepare for an instantaneous injection of 3 pu
current in the A phase, with no current in the B phase (B phase switch open). Connect a
timer to start when the fault injection is applied, and to stop when the trip occurs. To verify
correct output contact mapping use the trip contacts that would be expected to trip the circuit
breaker(s), as shown in the table. For two breaker applications, stop the timer once both
CB1 and CB2 trip contacts have closed. This can be achieved by connecting the contacts in
series to stop the timer.
Single breaker Two circuit breakers
Three Pole Tripping Any Trip Any Trip (CB1) and Any Trip (CB2)
Single Pole Tripping Trip A Trip A (CB1) and Trip A (CB2)
8.3.2.2 Phase B
Reconfigure the test equipment to inject fault current into the B phase. Repeat the test in
8.3.2.1, this time ensuring that the breaker trip conta
cts relative to B phase operation close
correctly. Record the phase B trip time. Switch OFF the ac supply and reset the alarms.
8.3.2.3 Phase C
Rep
eat 8.3.2.3 for the C phase.
The average
of the recorded operating times for the three phases should be less than 40 ms
for 50 Hz, and less than 35 ms for 60 Hz when set for instantaneous operation. Switch OFF
the ac supply and reset the alarms.
Note: For applications using magnetizing inrush current restraint, use a test
current higher than the [3313: Inrush High] setting to obtain fast
operating times. At least twice setting is recommended.
Where an IDMT or definite time delay is set in the GROUP 1 PHASE DIFF menu column, the
expected operating time is typically within +/- 5% of that for the curve equation plus the
“instantaneous” delay quoted above.
On completion of the tests any distance, overcurrent, earth fault or breaker fail elements
which were disabled for testing purposes must have their original settings restored in the
CONFIGURATION column.
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