ABB CM-IWM.10 Manual Del Usuario página 11

III Function diagram
a) Prewarning
b) Warning
Earth fault
Auto reset
Open-circuit principle
Closed-circuit principle
Yellow LED
Red LED
Manual reset
Reset button
Monitoring functions
The CM-IWM serves to monitor insulation resistance in
accordance with IEC/EN 61557-8 in unearthed IT AC systems, IT
AC systems with galvanically connected DC circuits, or unearthed
IT DC systems.
The insulation resistance between system lines and system earth
is measured. If this falls below the adjustable threshold values,
the output relays switch into the fault state.
When applying control supply voltage the green LED „PWR" turns
on and an internal selftest of 10 s starts, where the LEDs of the
indicator string light up in sequence. After this, measurement of
the insulation resistance in the measuring circuit begins.
Measuring principle
If the measuring circuit is activated, an active measuring voltage
with alternating polarity is applied between L(+)/L(-) and PE/KE
to measure the insulation resistance.
The length of the positive and negative measuring cycles
depends on the settings on the rotary switch „C
system leakage capacitance of the monitored network and, with
DC networks, on the level and duration of possible mains voltage
fluctuations. Correct and preferably quick measurement is thus
given with different mains conditions. In the event of particularly
unfavorable conditions and major interferences, the measuring
analysis can be steadied and delayed in addition with rotary
switch „t " if necessary.
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The current insulation resistance is determined and analysed
at the end of each measuring phase. The LED chain show the
resistance determined, and the output relays for prewarning
„VW" and warning „AL" switch according to the respective
threshold values set. If the threshold values have been undercut,
the LEDs „VW" or „AL" light according to the insulation fault
location: „+", „-" or „+" and „-" simultaneously for AC faults or
symmetric insulation faults.
Device test functions
The self-test of the device (2 measuring cycles at 4 s + 2 s pause)
is performed automatically after applying control supply voltage
and then every 4 operating hours. It can also be triggered
manually at any time by pressing the „Test" button at the device
front or with an external pushbutton connected between
terminals T and G. The status of the output relays is not affected.
The expanded test is started when the internal or external „Test"
button is pressed (or is still held) at the end of the self-test. The
sequence is the same as with the self-test, however, the output
relays „AL" and „VW" as well as the corresponding LEDs switch
to the alarm state.
English
Behaviour with internal device faults
If internal device faults were detected during the test function,
the LED „ERR" is lightening and the measuring circuit is
deactivated internally. The LED „Active" turns off. The output
relays „AL" and „VW" as well as the corresponding LEDs switch to
the alarm state and all LEDs of the LED chain turn off.
Behaviour with connection faults
Measurement is suspended if a line interruption is detected at
terminals L(+) / L(-); the LED „Active" turns off. This broken wire
detection is signalled by flashing S of the LED „ERR". The
output relays „AL" and „VW" as well as the corresponding LEDs
go into alarm state and all LEDs of the indicator LED chain turn
off.
Measurement of the connection insulation resistance restarts
after the connection interruption has been corrected. However,
stored alarm messages are preserved.
If the connections PE/KE to the protective conductor system
are interrupted, the same responses take place as with an
interruption at terminals L(+)/L(-), only that the LED „ERR"
flashes differently: U.
Attention!
• Disconnect the system and device from the power supply
and ensure they remain disconnected during electrical
installation.
• The voltage of the monitored voltage system is connected
to terminals L(+) / L(-).
• Please observe sufficient distance
E
neighbour devices and to the grounded metal cabinet or
box (min. 0.5 cm / 0.20 in).
• The terminals of the control inputs T, R and G have no
galvanic separation to the measuring circuit L(+) and L(-)
and are electrically connected together, therefore they
have to be controlled by volt free contacts or bridge. These
contacts or bridges must provide a sufficient separation
depending on the mains voltage on L(+)-L(-).
• No external potentials may be connected to control
terminals T and R. The associated reference potential is G
(identical with PE), and the connection of the terminals is
made via bridges to G.
• Before checking insulation and voltage, disconnect the
monitoring device from the power source.
• Only one insulation monitor may be active in a network to
be monitored, since the devices would otherwise influence
each other. When coupling several networks or incoming
feed sections, where each of them is equipped with its own
insulation monitor, all of them must be deactivated except
for one insulation monitor.
• Device terminals PE and KE must always be connected
via separate lines to different terminal points of the
protective-conductor system.
• The
connection.
• The measuring circuit should not be connected via longer
parallel guided wires, as this may interfere with the broken
wire detection. Also large capacities between L(+) und L(-)
have to be avoided.
Warning! Risk of electrocution!
Danger to life or risk of serious injuries!
device must not be
Please refer to the data sheet
2CDC112242D0201 for further safety
instructions!
to terminals of
operated without KE/PE
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