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21
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7. RCD TESTS
DISCONNECT THE INSTRUMENT FROM THE CIRCUIT UNDER TEST
BEFORE OPERATING THE FUNCTION SWITCH
TO SELECT THE RCD TEST RANGE SELECT“RCD”
7.1
Purpose of the RCD test
The RCD must be tested to ensure that operation takes place quickly enough
to ensure that there is unlikely to be serious danger to a person experiencing
an electric shock from the system. This test must NOT be confused with that
taking place when the "test" button on the RCD is pressed; operation of the
test button simply trips the breaker to ensure that it is working, but does not
measure the time taken to break the circuit.
7.2
What does the RCD test really do?
The RCD is designed to trip out when the difference between the phase
current and the neutral current (this is called the residual current) reaches the
tripping value (or rating) of the device. The tester provides a carefully preset
value of residual current depending on its setting and then measures the time
lapse between the application of the current and the operation of the RCD.
7.3
RCD testing
1．Press the test button once. Then, the instrument switches on.
2．Set the RCD rated tripping switch to the trip rating of the RCD under test.
3． Set the function switch to X1/2 for the "no trip" test, which ensures that the
RCD is operating within its specification and is not too sensitive.
4．Set the "LOOP/RCD" switch to 0°
5． Connect the instrument to the RCD to be tested either via a suitable
socket outlet（see fig 9）or using the OMA DIEC test lead set（see fig
10）.
6． Make sure that the P-E and P-N wiring check lamps are lit and the wiring
incorrect
LED is not lit. If they are not, disconnect the tester and check
the wiring for a possible fault.
7． If the lamps are correctly lit, press the test button to apply half the rated
tripping current for 2000 ms, when the RCD should not trip. The PN and
PE LEDs should remain on indicating the RCD has not tripped.
8． Repeat the test with the "LOOP/RCD" switch at 180°
9． In the event of the RCD tripping, the trip time will be displayed, but the
RCD maybe faulty.
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