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Function
18
isoLR275_D00127_00_M_XXEN/07.2018
2.4.6
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. If the input F1/F2 is bridged, the connec-
tions to the coupling device AK1/AK2 are switched off via internal coupling re-
lays, the measuring function is stopped and the message "STANDBY" appears
on the display. Instead of the most recently measured value the value > 1 MΩ
will be indicated. Furthermore, the alarm relays and alarm LEDs stop signal-
ling alarm messages.
After opening the function input F1/F2, the connection to the IT system will
be restored and a completely new insulation resistance measurement cycle is
started.
This function can be used to disconnect an isoLR275 selectively in IT systems
via the auxiliary contacts of the respective coupling switch. One coupling
switch each in a line-type or ring-type arrangement can deactivate a subse-
quent isoLR275 to ensure that only one ISOMETER® is active in each galvani-
cally connected IT system.
If in a ring-type arrangement all coupling switches are closed, theoretically all
ISOMETER®s would be deactivated. In order to prevent this, a BMS master
(BMS addr. 1) 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 insu-
lation monitoring function of the master ISOMETER® and hence the function
input F1/F2 of the master are without function in this mode. Details are illust-
rated in the graphic below: