isoNAV685-D_D00215_02_M_XXEN/04.2017
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Function
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.
• Combination of
and other profile-specific measurement methods.
• An adjustable response value for insulation monitoring in the range of 1 kΩ…10 MΩ
(factory setting = 5 kΩ) and a response value of 150 V for the DC offset voltage.
• High-resolution graphic LC display for excellent readability and recording of the
device status.
• Connection monitoring (monitoring of the measuring lines).
• Automatic device self test.
• History memory with real-time clock (buffer for three days) for storing 1023 alarm
messages with date and time.
• Current and 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).
• Worldwide remote diagnosis via the Internet (made available by Bender Service
only)
• BCOM, Modbus TCP and web server
3.2 Product description
The ISOMETER® isoNAV685-D is an insulation monitoring device in accordance with IEC
61557-8 for IT systems. It is applicable for use in 3(N)AC systems.
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3.3 Functional description
The insulation monitoring device ISOMETER® isoNAV685-D-B continuously monitors the
entire insulation resistance of an IT system during operation and gives a warning within
150 ms as soon as the insulation resistance falls below the set response value and the DC
offset voltage exceeds the response value.
Because of these characteristics, the ISOMETER® can, for example, quickly shut down a
plant.
To obtain a measurement the device has to be connected between the IT system (un-
earthed system) and the protective earth conductor (PE). A measuring current in the µA
range is superimposed onto the system which is recorded and evaluated by a micro-con-
trolled measuring circuit. The measuring time is dependent on the selected measure-
ment profiles, the system leakage capacitance, the insulation resistance 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 lan-
guages can be selected for the setup menus as well as the messages indicated on the dis-
play. The device utilises a clock for storing fault messages and events in a history memory
with time and date stamp. The settings can be protected against unauthorised modifica-
tions by entering a password. To ensure proper functioning of connection monitoring,
the device requires the setting of the system type 3AC and the prescribed wiring of the
appropriate terminals
L1/+, L2, L3/-.
The insulation monitoring device iso685 is able to measure the insulation resistance reli-
ably and precisely in all common IT systems (unearthed systems). Due to various applica-
tions, system types, operating conditions, application of variable-speed drives, high
system leakage capacitances etc., the measurement technique must be able to meet var-
ying requirements in order to ensure an optimised response time and relative uncertain-
ty. Different measurement profiles, which can be selected from a setup menu, allow
optimum adaptation of the measurement technique to the specific application.
