KYORITSU 6010B - Manual (Page 23)

DISCONNECT THE INSTRUMENT FROM THE CIRCUIT UNDER TEST
BEFORE OPERATING THE FUNCTION SWITCH
TO SELECT THE RCD OR UC TEST RANGE SELECT "RCD" OR "UC"
8.1 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.
8.2 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.
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8. RCD/Uc TESTS
Fig 12