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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.