User Manual

GMC-I Messtechnik GmbH 57
14.5 Testing of Insulation Monitoring Devices – IMD Function
(PROFITEST MXTRA & SECULIFE IP only)
Applications
Insulation monitoring devices (IMDs) or earth fault detection sys-
tems (EDSs) are used in IT systems in order to monitor adherence
to a minimum insulation resistance value, as specified by
DIN VDE 0100-410.
They’re used in power supplies for which a single-pole earth fault
may not result in failure of the power supply, for example in oper-
ating rooms or photovoltaic systems.
Insulation monitors can be tested with the help of this special
function. After pressing the ON/START button, an adjustable insula-
tion resistance is activated between one of the two phases of the
IT system to be monitored and ground to this end. This resistance
can be changed in the “MAN±” manual sequence mode with the
help of the “+” or “–” softkey, or varied automatically from R
max
to
R
min
in the “AUTO” operating mode. Testing is ended by once
again pressing the ON/START key.
Time during which the momentary resistance value prevails since
changing the value at the system is displayed. The IMD’s display
and response characteristics can be subsequently evaluated and
documented with the help of the “OK” or “NOT OK” softkey.
Connection L – N
When selecting test resistance, don’t forget that an excessively
high test current could damage sensitive system components.
Set Parameters
Measuring Procedure (1)
There are two ways to conduct the test:
– MAN: Resistance is changed manually be pressing softkeys.
– AUTO: Resistance is changed automatically every 2 seconds
beginning with R
START.
Resistance RSTART (3)
Numerous parameters are available for setting resistance RSTART,
with which measurement is begun.
Conductor Relationship / Resistance Range (2)
– Conductor relationship: The corresponding conductor relation-
ship can be selected for documentation of the measuring
point.
– Resistance range: A range of values can be adjusted for testing
the display of resistance at the IMD.
The parameter is set as a percentage with reference to the resis-
tance momentarily introduced by the test instrument.
Upper and lower limit values are displayed in the measuring view.
Measuring Procedure
➭ Set the parameters.
➭ Start: Press the ON/START key.
➭ A resistance is introduced between the phase and protective
conductors and time measurement is started.
➭ Manual test – MAN + –: Press the or key to increase
or reduce test resistance R
L-PE
➭ Automatic test – AUTO: Resistance is changed automatically.
➭ Tripping time ta is restarted each time resistance is changed.
➭ Press IΔ
N
in order to change the conductor relationship.
➭ In order to end measurement, press ON/START as soon as the
IMD indicates that insulation resistance has been fallen short
of.
➭ Display of measured values
➭ Evaluation prompt: Measurement OK?
➭ In case of an evaluation of NOT OK the UL/ RL LED lights up red.
➭ Press the softkey to save.
1
3
2
Conductor
Relationship: