ABB SPAJ 111 C User Manual page 13

The low-set stage of the earth-fault relay func-
tions as back-up protection for the outgoing
feeders and the high-set stage as the busbar
earth-fault protection. If the earth- fault appears
on an outgoing feeder the start signal of the
feeder earth-fault relay blocks the earth-fault
relay of the incoming feeder. If the earth-fault
appears on the busbars no blocking signal is
obtained and the earth-fault relay of the infeeder
trips. The incoming blocking signal is routed to
the high-set stage of the earth-fault relay module
SPCJ 1C7 with switch SGB/5.
The fault current is measured with a current
transformer between the neutral point of the
low-voltage side of the power transformer and
earth or between the neutral point of a generator
and earth.
The high-set stage of the earth-fault relay trips
the circuit breaker on the high-voltage side of
the power transformer and the busbar earth-
fault is rapidly isolated. The low-set stage trips
the circuit breaker of the low-voltage side of the
power transformer. Operate times down to 100
ms can be achieved at busbar earth-faults.
Switch SG1/SPCJ 1C7
1 1 t> = 0.5...10 s
2 0
}
I > = 1...10% x I
0
3 0
4 0 no latching
5 0 not in use
6 0
}
I >> = 5...40% x I
0
7 0
8 0 t>> = 0.05...1.00 s
Σ
1
When the switches are set as above, the output
contacts of relay SPAJ 111 C provide the follow-
ing signals:
Contact Function
65-66 Circuit breaker trip signal, stage I
68-69 Circuit breaker trip signal, stage I
80-81 Signal on tripping, stage I
77-78 Signal on tripping, stage I
73-74-75 Start signal, stage I
70-71-72 Self-supervision signal
When an earth-fault appears somewhere in the
earthed network a part of the fault current flows
through the neutral earthing resistor. The bus-
bar earth-fault relay starts on the same faults as
the earth-fault relays of the feeders connected to
the transformer. When the busbar earth-fault
relay is used as a back-up relay for the earth-fault
relays of the outgoing feeders the operate time of
the busbar relay must be longer than the operate
time of the feeder earth-fault relays. The busbar
earth-fault relay in the above example can also
be used for the detection of high-resistance
earth-faults. When the busbar earth-fault relay
is used for signalling only, the earth-fault relay
can also be used for disconnection of the earth-
ing resistor in order to lower the earth-fault
current.
In the example the trip contact of the earth-fault
relay is latching (SG1/4=1). The latched output
relay can be reset with the push-button on the
front panel or with a command via the serial bus.
The selector switches of the earth-fault relay
SPAJ 111 C can be set as follows:
SGB/SPCJ 1C7
0 not in use
0 not in use
n
0 not in use
0 stage t> not blocked
1 stage t>> blocked
0 not in use
n
0 not in use
0 not in use
>
0
>>
0
>
0
>>
0
>
0
SGR
1 blocking signal from feeders
0 no I >> start signal to relay D
0
0 no I > start signal to relay D
0
1 I >> trip signal to relay D
0
0 no I >> trip signal to relay C
0
0 no I >> trip signal to relay A
0
1 I > trip signal to relay C
0
0 no I > trip signal to relay B
0
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