Answer / raghavendran

Checking of the pickup and dropout value

When checking the pickup value, the analogue input signals
of the single phase alternating test current have to be fed
to the relay via terminals.When testing the pickup value,
the alternating test current must first be lower than the
set pickup value.
Then the current will be increased until the relay picks up.
The value that can be read from the ammeter may not deviate
by more than ± 2.5% of the setting value. The tripping
values for the other current inputs should be checked
accordingly.

Function test
Disconnect all leads for adjusting the interposing C.T.s and
perform the following function test:
Load the generator with minimum 50% load. Assure that the
tripping of the generator C.B. does not cause un-wanted
damages (blackout).
To operate the differential relay use a shorting link
between one of the phase measuring sockets
and GND, e.g. connect Line to GND. The relay should trip
immediately. If no trip occurs, make sure
that the load current exceeds the set value.

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