Question: What fault currents are applied to test RCD trip times
Answer: Dependent on the type selected : AC or A or B.
Each RCD can have up to 6 tests at variations of its nominal mA rating :- x1/2, x1, x5 repeated at 0° and 180° (on +ve and -ve half cycles of the supply).
At x1/2 nominal, the RCD should not trip, at x1 and x5 it should trip, to ensure this functionality the tests have an offset in their specification.
Instead of the usual ± specification they are declared as...
x1/2 is specified as -10% to 0% (cannot be more than x1/2).
x1 & x5 are specified as 0% to +10% (cannot be less than x1 & x5).
The half cycle is determined by the direction that the sine wave crosses 0V,
from negative to positive indicates a positive half cycle 0°
from positive to negative indicates a negative half cycle 180°
The test current and timing begin at these points.
Besides the value applied, also the waveshape is important and dependent on the type selected:
Type AC setting uses a sinusoidal fault current with an RMS value of (nominal value x multiplier).
for a 30mA RCD on a x1/2 test this would be (30 mA x 1/2) = 15mA RMS,
applying the specification (-10% to 0%) gives a range of 13.5 mA RMS to 15 mA RMS.
for a 10mA RCD on a x5 test this would be (10 mA x 5) = 50mA RMS,
applying the specification (0% to +10%) gives a range of 50 mA RMS to 55 mA RMS.
Type A setting uses a half wave rectified fault current, the RMS value of which matches the required pulsed DC level.
Requirements of IEC 61008/9 give the following test current values…
Where the multiplier is x1/2 and for all nominal values, test current = 0.7 x nominal x multiplier.
Where the multiplier is x1 or x5, for 10mA nominal value, test current = 2 x nominal x multiplier.
Where the multiplier is x1 or x5, for all other nominal values test current = 1.4 x nominal x multiplier.
(from RMS values of half wave rectified waveforms √2 =1.414, 1 ÷ √2 = 0.707).
for a 30mA RCD on a x1/2 test this would be (0.7 x 30mA x 1/2) = 10.5 mA RMS,
applying the specification (-10% to 0%) gives a range of 9.45 mA RMS to 10.5 mA RMS.
for a 10 mA RCD on a x1 test this would be (2 x 10 mA x 1) = 20 mA RMS,
applying the specification (0% to +10%) gives a range of 20 mA RMS to 22mA RMS.
for a 10 mA RCD on a x5 test this would be (1.4 x 10 mA x 5) = 70 mA RMS,
applying the specification (0% to +10%) gives a range of 70 mA RMS to 77mA RMS.
Type B setting produces a smooth DC current at the required value (nominal value x multiplier).
for a 30mA RCD on a x1/2 test this would be (30mA x 1/2) = 15 mA DC,
applying the specification (-10% to 0%) gives a range of 13.5 mA DC to 15 mA DC.
for a 10 mA RCD on a x5 test this would be (10 mA x 5) = 50 mA DC,
applying the specification (0% to +10%) gives a range of 50 mA DC to 55mA DC.