5.5 General Information Regarding RCD Tests
For evaluating the perfect functioning of a residual
current circuit breaker the essential measurement
units are the contact voltage generated during RCD
trip and the trip time required by the RCD to dis-
connect the subsequently connected current circuit
from the mains.
Therefore, DIN VDE 0100 prescribes that:
a) the maximum admissible value of the contact
voltage for tripping at nominal fault current with-
in a system must not be exceeded, -
b) the residual current circuit breaker trips within
300 ms.
The task of a residual current device consists in
switching off a system within 300 ms after the oc-
currence of a body current, prior to the contact volt-
age reaching the admissible limit value of 25 V or
50 V. The limit value 25 V is valid for agricultural and
medical systems. For all other systems the value of
50 V is valid.
The instrument UNITEST 0100-ELECTROcheck
works with a limit value of 25 V. Thus, the respect
of the limit value is guaranteed for all systems.
The test of the system should commence by an in-
spection, in particular of the protective conductor
connection:
1. In TT systems the protective conductor must not
be connected with the PEN but with the local
protective earth.
2. In TN systems the protective conductor must be
connected to the PEN ahead of the RCD.
3. An insulation test in compliance with the de-
scription in section 5.2 must be carried out. It
must be determined in particular that no con-
nection exists between N and PE following the
RCD.
4. A proof regarding the low impedance nature of
the equipotential bonding conductor connec-
tion in compliance with section 5.1 must be
available.
When performing tests on shockproof sockets
or equipments with protective conductor con-
nection, the orderly connection of the protec-
tive conductor must be checked. For this pur-
pose, briefly touch the contact electrode ‘PE’
(21) of the test instrument after having con-
nected the test leads and prior to starting the
test procedure. If an acoustic sound is audible
and the symbols ‘”
” (14) and 'PE Failure'
(16) are displayed, the PE connection must be
checked! The test may only be started after
having corrected the protective conductor con-
nection! During protective conductor testing it
must be ensured that the measurement result
is not influenced by an insulated floor or site.
Test and measurement procedures within net-
works secured by residual current devices
should only be performed after having con-
tacted the operators of the instruments con-
nected (data processing systems, process
technology, motors, etc.).
Leakage currents in current circuits following
the RC circuit breaker may have an influence
on the test as well as a voltage between pro-
tective conductor or neutral conductor and
ground.
As the neutral conductor (N) is used to mea-
sure the contact voltage, this conductor must
be checked prior to the RCD test. For this pur-
pose, the mains internal resistance test is ap-
propriate.
If a contact voltage between neutral conductor
(N) and protective conductor (PE) higher than
25 V is measured during the test, the test pro-
cedure is immediately interrupted and the sym-
bols ”
” (14) contact voltage’ (15) and (6)
are displayed.
21
General Information Regarding RCD Tests
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