GMC-I Messtechnik GmbH
19
7.3
Testing for Special RCDs
7.3.1
Systems with Type RCD-S Selective RCDs
Selective RCDs are used in systems which include two series
connected RCCBs which are not tripped simultaneously in the
event of a fault. These selective RCDs demonstrate delayed
response characteristics and are identified with the symbol
.
Measuring Method
The same measuring method is used as for standard RCCBs (see
sections 7.1 on page 15 and 7.2.1 on page 17).
If selective RCDs are used, earthing resistance may not exceed
half of the value for standard RCCBs.
For this reason, the instrument displays twice the measured value
for contact voltage.
Select the Measuring Function
Set Parameters – Selective
Start Measurement
Tripping Test
Ð
Press the I
N
key. The RCCB is tripped. Blinking bars appear
at the display panel, which is followed by the display of time to
trip t
A
and earthing resistance R
E
.
The tripping test need
only be performed at
one measuring point for
each RCCB.
Note
Selective RCDs demonstrate delayed response
characteristics. Tripping performance is briefly influenced
(up to 30 s) due to pre-loading during measurement of
contact voltage. In order to eliminate pre-loading caused
by the measurement of contact voltage, a waiting period
must be observed prior to the tripping test. After the
measuring sequence has been started (tripping test),
blinking bars are displayed for approximately 30 sec-
onds. Times of up to 1000 ms are allowable. The tripping
test is performed immediately by pressing key I
N
.
7.3.2
PRCDs with Non-Linear Type PRCD-K Elements
The PRCD-K is a portable differential current system with elec-
tronic residual current evaluation which, being conceived as an
intermediate cable device, switches at all poles (L/N/PE). The
PRCD-K also includes undervoltage tripping and protective con-
ductor monitoring.
As the PRCD-K features undervoltage tripping, it must be oper-
ated at line voltage, and measurements may only be performed
when it is activated (PRCD-K switches at all poles).
Terminology (from DIN VDE 0661)
Portable protective devices are circuit breakers which can be con-
nected between power consuming devices and permanently
installed electrical outlets by means of standardized plug-and-
socket devices.
A reusable, portable protective device is a protective device which
is designed such that it can be connected to movable cables.
Please be aware that a non-linear element is usually integrated
into PRCDs, which leads to immediate exceeding of the greatest
allowable contact voltage during U
I
measurements (U
I
greater
than 50 V).
PRCDs which do not include a non-linear element must be tested
in accordance with section 7.3.3 on page 20.
Objective (from DIN VDE 0661)
Portable residual current devices (PRCDs) serve to protect per-
sons and property. They allow for the attainment of increased lev-
els of protection as provided by protective measures utilized in
electrical systems for the prevention of electrical shock as defined
in DIN VDE 0100, part 410. They are to be designed such that
they can be installed by means of a plug attached directly to the
protective device, or by means of a plug with a short cable.
S
I
N
I
F
or
Type 1:
