User Manual

50 GMC-I Messtechnik GmbH
12.2 Protective Conductor Resistance Measurement with Ramp Curve
– Measurements on PRCDs with Current-monitored Protective Conductor Using PROFITEST PRCD Test Adapter as Accessory
Application
In certain PRCD types, the protective conductor current is moni-
tored. Direct application or disconnection of the test current of
200 mA, which is required for protective conductor resistance
measurements, results in tripping of the PRCD and, conse-
quently, a cut-off of the protective conductor connection. Protec-
tive conductor measurement is no longer possible in this case.
A special ramp curve for the application or disconnection of the
test current in combination with the PROFITEST PRCD test adapter
allows for performing protective conductor resistance measure-
ments without PRCDs being tripped.
Timed Sequence of the Ramp Function
Due to the physical properties of the PRCD, the measuring cycles
of this ramp function lie within the range of several seconds.
Moreover, while the polarity of the test current is being reversed,
an additional waiting period during polarity reversal becomes nec-
essary.
This waiting period has been included in the test sequence in
operating mode „automatic polarity reversal“ .
If you change the polarity direction manu-
ally, e.g. from „+pole with ramp“
to „–pole with ramp“
, the test instrument recog-
nizes the change in the current flow direc-
tion, disables measurements for the
required waiting period and simultane-
ously shows the respective symbol, see figure on the right.
Visualization of the measuring and waiting phases during protective con-
ductor resistance measurements on PRCDs with the PROFITEST MXTRA
Tripping of a PRCD due to faulty contact
During measurement, safe contact between the test probes of the
2-pole adapter and the DUT or the sockets of the PROFITEST PRCD
test adapter is to be ensured. Interruptions may lead to heavy
fluctuations in the test current which may cause the PRCD to trip
in the worst case.
In this event, the tripping of the PRCD is
automatically recognized by the test
instrument as well and an error message
is generated, see figure on the right. In
this case as well, the test instrument
automatically takes into account the
required waiting period before re-
enabling the PRCD and allowing any new measurements.
Connection
➭ Please consult the operating instructions of the PROFITEST
PRCD adapter, particularly chapter 4.1. There you will also find
information on the connection terminals for offset measure-
ments and protective conductor resistance measurements.
Selecting Polarity Parameter
➭ Select the requested polarity parameter with
ramp.
Measuring ROFFSET
➭ Perform an offset measurement as described on page 48, to
assure that the test adapter‘s connector contacts are not in-
cluded in the measurement results.
Note
The offset only remains saved to memory until you
change the polarity parameter. If you perform the mea-
surement with manual polarity reversal (+pole or –pole),
you have to repeat the offset measurement before each
measurement with another polarity.
Measuring Protective Conductor Resistance
➭ Check whether the PRCD is activated. If this is not the case,
activate it.
➭ Perform the protective conductor measurement as described
above in section 12.1. Start the test sequence by briefly
pressing key ON/START. By pressing and holding key ON/START
you can extend the preset duration of the measuring phase.
Start measurement
During the magnetization phase (rising curve) and the
subsequent measuring phase (constant current) the
symbol on the right is shown.
If you abort the measurement during the rise phase, no measur-
ing result can be issued and displayed.
After the measurement, the demagnetization phase
(declining curve) and a subsequent waiting period is sig-
nalled with the inverse symbol shown on the right.
During this period, no new measurements are possible.
Only when the symbol on the right is shown, can the
measurement result be read and measurements started
with the same or another polarity.
Measuring phase Demagnetization
and waiting period
Result
Time [s]
Rise
phase
Test Current [ A]
01 3 6
0.25
prior to polarity reversal
or
restart