Operation Manual

56 GMC-I Messtechnik GmbH
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
Set Parameters
– MAN/AUTO (1)
Switch between manual
measuring sequence
MAN
and automatic measuring
sequence AUTO
– Change conductor
relationship and limit
values (2)
Quick switching between
L1-PE and L2-PE (also
during measurement) with
the I
 N
key
– Changing the initial resistance (3)
You can select the initial
resistance here to start
each series of measure-
ments for manual mea-
suring sequences.
The GOME setting
(default settings) sets
the initial value to a
resistance value of
50.0 k.
Set Limit Values for R
L-PE
as %
Limit values are calculated and displayed as a percentage of the
momentarily displayed R
L-PE
value.
Manual Measuring Sequence
The measurement and the stopwatch (see arrow) are started with
the “START” key.
The stopwatch is restarted each time the resistance value is
changed and whenever the energized phase conductor is
switched (L1/L2).
During measurement, the conductor relationship (L1-PE or L2-
PE) can be changed with the I
N
key or the resistance value can
be adjusted with the + and – keys, without interrupting the mea-
surement. The stopwatch is reset in both cases.
Increasing + or Decreasing – the Resistance Value
(The setting values themselves are fixed!)
The bar graph display provides you with quick orientation. The
numeric combination which appears below it indicate the
momentary step from as many as 65 steps (in this case step 17 of
65).
Automatic Measuring Sequence
In the case of the automatic measuring sequence, the sequence
runs through all resistance values from the maximum to the mini-
mum value (Rmax (2,51 M) to Rmin (20 k)) in 65 steps, and
dwell time for each step is 2 seconds.
1
3
2
Limit value:
I < and I > limit values
U
L
 R
L