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7.
Commissioning
Firstly,
chec~
that the connect,ions of current transformers, tripp-
ing and alarm connections as well as the polarity of the auxiliary
supply are correct:
1. Check ratio and connections of C.T.s
}
(fig. 3 or 8)
Check auxiliary supply voltage and polarity
2. Check response of relay at your settings:
CAUTION:
When removing or restoring connections, the accepted
safety practices and regulations must be observed. Dur-
__
ing all measurements take care that the thermal capacity
is not exceeded (see fig. 10).
•
•
a) Remove transparent front cover. The external C.T. is automati-
cally short-circuited and disconnected from relay.
b) Using test plug with the associated cable 7XV81 (which includes
the trip circuit output - see figure
9)
check the operating
time at one or two points on the characteristic, one with a
test current of approximately four times plug setting and one
at a higher value if possible (Siemens test sets 7VP44 or
1VP461
may be used for this purpose). The permissible toler-
ance should not 'exceed
~
20
%
(according to BS 142) •
Should larger tolerances exist then, as a first step, the test
set-up should be checked:
superimposed load current
shunt circuit for test current
}
not possible if
1XV81
is used for testing
test current not constant during relay delay time
test current not injected (in particular for C.T.-powered
relays).
If after checking the above points an excessive tolerance exists
then the complete relay should be returned for repair. Do not
attempt recalibration.
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