Bender ISOMETER IRDH575, Manual

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Function
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IRDH575_D00089_05_M_XXEN/01.2020
3.5.5 Function input F1/F2 for connection or disconnection of IT
systems being monitored
The ISOMETER® can be disconnected from the IT system and set to STANDBY
mode with the function input F1/F2. When the input F1/F2 is bridged, the ter-
minals L1/L2 are isolated from the measuring circuit via internal coupling re-
lays and terminal L3 remains connected to the measuring circuit via a resistor
of 10 MΩ. The measuring function is stopped and the message „STANDBY“ ap-
pears on the display. When using software version 1.4 or higher, the latest
measured insulation resistance is blanked and the value > 10 MΩ appears on
the display. Furthermore, the alarm relays and alarm LEDs no longer provide
alarm messages. Insulation faults already detected will be indicated by all
EDS4…devices.
After opening the function input F1/F2, first of all the connection to the IT sys-
tem will be restored and a completely new measuring cycle for insulation mo-
nitoring will be started. Using this function, selective disconnection of an
IRDH575 in interconnected IT systems can be carried out via auxiliary contacts
of the respective coupling switch. One coupling switch each in a line-type or
ring-type arrangement can deactivate a subsequent IRDH575. This arrange-
ment guarantees that only one ISOMETER® is active in each galvanically con-
nected IT system.
Theoretically speaking, in a ring-type arrangement with all coupling switches
closed, all ISOMETER®s would be deactivated. In order to prevent this, a BMS
Master (IRDH575 Adr1) monitors the condition of the function input F1/F2 of
all Slave ISOMETER®s.
When all Slave ISOMETER®s are in the STANDBY mode, the insulation monito-
ring function of the Master ISOMETER® remains active, that means, the input
F1/F2 of the Master is without function in this mode.