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isoNAV685-D-B_D00264_03_M_XXEN/06.2017
10
Function
3. Function
3.1 Features
• ISOMETER® to monitor the insulation resistance in systems that are switched off.
• Automatic adaptation to the existing system leakage capacitance.
•
measurement method.
• An adjustable response value in the range 1 kΩ…10 MΩ
(factory setting = 50 kΩ).
• High-resolution graphic LC display for excellent readability and recording of the
device status.
• Ground fault monitoring.
• Automatic device self test.
• History memory with real-time clock (buffer for three days) for storing 1023 alarm
messages with date and time.
• Freely programmable digital inputs and outputs.
• Remote setting of certain parameters via Internet
(Option; COMTRAXX® Gateway).
• Worldwide remote diagnosis via Internet.
• Modbus TCP, web server and BCOM.<
3.2 Product description
The ISOMETER® isoNAV685-D-B is an insulation monitoring device for IT systems in ac-
cordance with IEC 61557-8. It is universally applicable in TN, TT or IT systems that are
switched off.
*
3.3 Functional description
The insulation monitoring device ISOMETER® isoNAV685-D-B monitors the entire insula-
tion resistance of systems that are switched off and triggers an alarm when the insulation
resistance value falls below a preset response value.
The insulation resistance of the L1, L2 and L3 coupling paths is measured sequentially.
This means that faults are not only measured, but they can also be localized or located.
The test time may vary, e.g. it may be longer, depending on the leakage capacitance.
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/-.