a trip-out time delay. This type of RCD is specifically designed
for installations where the selectivity characteristic is required.
In order to ensure the protection of an electrical installation
protected by RCD's, they should be checked to confirm the
trip-out time tΔ is correct.
The trip-out time tΔ is the time required by the RCD to trip at
a rated residual operating current of IΔn. The standard values
of tripping time are defined by IEC 61009 (EN61009) and IEC
61008 (EN 61008) and are listed in the table below for IΔn
and 5IΔn.
Type of RCD IΔn
General(G)
300ms
max allowed value
Selective(S)
500ms
max allowed value
130ms
min allowed value
* Maximum 5IΔn tripping time is limited to 50 ms as required
by BS7671 when 'OL' is displayed.
5 IΔn
40ms
max allowed value
*150ms
max allowed value
*50ms
min allowed value
— 7 —
Typical examples of instrument connection:
Practical example of 3-phase + neutral RCD test in a TT
system.
Fig. 2
Practical example of single phase RCD test in a TN system.
Fig. 3