Function; Features; Product Description; Function Description - Bender ISOMETER isoRW685W Manual

3. Function

3.1 Features

• ISOMETER® for IT AC systems with galvanically connected rectifiers or inverters and
for IT DC systems (IT = unearthed systems)
• Automatic adaptation to the existing system leakage capacitance
AMP PLUS
• Combination of and other profile-specific measurement methods
• Two separately adjustable response value ranges of 1 kΩ...10 MΩ
• High-resolution graphical LC display
• Connection monitoring (monitoring of the measuring lines)
• Automatic device self test
• Graphical representation of the insulation resistance over time (isoGraph)
• History memory with real-time clock (buffer for three days) for storing 1023 alarm
messages with date and time
• Current or voltage output 0(4)...20 mA, 0...400 μA, 0...10 V, 2...10 V (galvanically
separated), which is analogous to the measured insulation value of the system
• Freely programmable digital inputs and outputs
• Remote setting via the Internet or Intranet
(Webserver/Option: COMTRAXX® gateway)
• Remote diagnosis via the Internet (made available by Bender Service only)
• RS-485/BS (Bender sensor bus) for data exchange with other Bender devices via
Modbus RTU protokcol
• BCOM, Modbus TCP und web server

3.2 Product description

The ISOMETER® is an insulation monitoring device for IT systems in accordance with
IEC 61557-8 and is specially tested for railway applications according to DIN EN 50155.
It is universally applicable in AC, 3(N)AC, AC/DC and DC systems. AC systems may include
extensive DC-supplied loads (such as rectifiers, inverters, variable-speed drives).
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Function

3.3 Function description

The insulation monitoring device continuously monitors the entire insulation resistance
of an IT system during operation and triggers an alarm when the value falls below a pre-
set response value. To obtain a measurement the device has to be connected between
the IT system (unearthed system) and the protective earth conductor (PE). A measuring
current in the ?A range is superimposed onto the system which is recorded and evaluated
by a microprocessor-controlled measuring circuit. The measuring time is dependent on
the selected measurement profiles, the system leakage capacitance, the insulation re-
sistance and possible system-related disturbances.
The response values and other parameters are set using a commissioning wizard as well
as via different setup menus using the device buttons and a high-resolution graphical LC
display. The selected settings are stored in a permanent fail-safe memory. Different
languages can be selected for the setup menus as well as the messages indicated on the
display. The device utilises a clock for storing fault messages and events in a history
memory with time and date stamp. The settings can be password protected to prevent
unauthorised changes.
To ensure proper functioning of connection monitoring, the device requires the setting
of the system type 3AC, AC or DC and the required use of the appropriate terminals L1/+,
L2, L3/-.
The insulation monitoring device iso685... is able to measure the insulation resistance
reliably and precisely in all common IT systems (unearthed systems). Due to various
applications, system types, operating conditions, application of variable-speed drives,
high system leakage capacitances etc., the measurement technique must be able to meet
varying requirements in order to ensure an optimised response time and relative
uncertainty. Therefore different measuring profiles can be selected with which the device
can optimally adjusted.
If the preset response value falls below the value of Alarm 1 and/or Alarm 2, the associa-
ted alarm relays switch, the LEDs ALARM 1 or ALARM 2 light and the measured value is
shown on the LC display (in case of insulation faults in DC systems, a trend graph for the
faulty conductor L+/L- is displayed). If the fault memory is activated, the fault message
will be stored. Pressing the RESET button resets the insulation fault message, provided
that the current insulation resistance displayed at the time of resetting is at least 25 %
above the actual response value.
As additional Information, the quality of the measuring signal and the time required to
update the measured value are shown on the display. A poor signal quality (1-2 bars) may
be an indication that the wrong measurement profile has been selected.
isoRW685W-D_D00178_04_M_XXEN/02.2019