400 Series
EN - 76
14.4. WORKING TEST OF RCDS
14.4.1. Purpose of the test
Check whether general and selective RCDs have been installed and adjusted properly and
whether they maintain their features over the time. The check shall confirm that the RCD
trips at a current IdN lower than its rated working current IdN and that the tripping time
meets, depending on the case, the following conditions:
Does not exceed the maximum time provided by the standards in case of general type
RCDs (according to Tab. 5).
Is included between the minimum tripping time and the maximum one in case of
selective type RCDs (according to Tab. 5).
The RCD test effected by means of the test key is aimed at preventing “the gluing effect”
from compromising the working of the RCD which has been inactive for a long time;
therefore this test is effected only to verify the mechanical working of the RCD and it does
not permit to declare that the RCD is complying with the standards. According to a
statistical survey the periodical check, once a month, of the RCDs by means of the test
key reduces by one half the RCD fault rate, this test however detects only 24% of
defective RCDs.
14.4.2. Installation parts to be checked
All the RCDs shall be tested when installed. In the low voltage installations the test is
recommended to grant an acceptable safety level. For the medical rooms this check shall
be effected periodically every six months on all RCDs.
14.4.3. Allowable values
To compare the measurements make reference to the table reporting the limits for the
tripping times. On each RCD it is necessary to effect: a test with leakage current in phase
with voltage and a leakage current phase shifted by 180° with respect to the voltage. The
highest time is to be considered as significant result. The test at ½IdN shall never cause
the RCD tripping.
RCD type IdN x 1 IdN x 2 IdN x 5 * Description
General 0,3s 0,15s 0,04s Max tripping time in seconds
Selective S
0,13s 0,05s 0,05s Min tripping time in seconds
0,5s 0,20s 0,15s Max tripping time in seconds
* For nominal values IdN 30mA, the test current for 5 times is 0.25A
Tab. 5: Tripping times for general and selective RCDs
14.4.4. Note
In case the earth installation is not available effect the test connecting the instrument with
one terminal on a conductor downstream the RCD and one terminal on the other
conductor upstream the RCD itself.
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