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Interconnected systems
When using ISOMETERs
®
in IT systems care shall be taken that only one active
ISOMETER
®
may be connected in each conductive interconnected system. If IT
systems are interconnected via coupling switches, it is essential to ensure that
ISOMETERs not currently used must be disconnected and deactivated via a
control system before starting. IT systems coupled via diodes or capacitances may
also influence the insulation monitoring process. Hence, also in this case a central
control of the different ISOMETERs is required.
There are two possibilities to guarantee safe insulation monitoring in intercon-
nected IT systems.
Function input F1/F2
The ISOMETER
®
can be disconnected from the IT system and set to STANDBY
mode with the function input F1/F2. If the input F1/F2 is bridged, the connec-
tions L1/L2 are switched off via internal coupling relays, the measuring function
is stopped and the message „STANDBY“ is issued on the display. After opening
the input F1/F2, at first the connection to the IT system will be restored, then a
completely new measuring cycle for insulation monitoring will be started.
This function allows selective disconnection of an IRDH375B via auxiliary
contacts of coupling switches in interconnected IT systems. One coupling switch
each in a line-type or ring-type arrangement can deactivate the next IRDH375B
downstream. This arrangement guarantees that one ISOMETER per each galvani-
cally connected IT system is active.
In a ring-type arrangement with all coupling switches closed it can be assumed
that all ISOMETERs are deactivated. In order to prevent this, a BMS Master
(IRDH375B Ad1) monitors the condition of the function input F1/F2 of all Slave
ISOMETERs. If all Slave ISOMETERs are in the STANDBY mode, the insulation
monitoring function of the Master ISOMETER and hence the function input F1/F2
of the Master are without function in this mode.
Function
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