Function
16
isoPV425_D00028_09_M_XXEN/05.2018
switch back to their initial position and the alarm LEDs "AL1"/"AL2" stop
lighting. If the fault memory is activated, the alarm relays remain in the alarm
condition and the LEDs light until the reset button "R" is pressed or the supply
voltage is interrupted.
The device function can be tested using the test button "T". Parameters are as-
signed to the device via the LCD and the control buttons on the front panel;
this function can be password-protected. Parameterisation is also possible via
the BMS bus, for example by using the BMS Ethernet gateway (COM465IP) or
the Modbus RTU.
3.2.1 Monitoring the insulation resistance
The two parameters that monitor the insulation resistance, "R1" and "R2", can
be found in the response value menu "AL" (see table in Chapter 5.3). The value
R1 can only be set higher than the value R2. If the insulation resistance R
F
reaches or falls below the activated values R1 or R2, an alarm message will be
signalled. If R
F
exceeds the values R1 or R2 plus the hysteresis value (see the
table in Chapter 5.3.1), the alarm will be cleared.
The isoPV 425 determines the system leakage capacitance C
e
through an impedance measurement whose frequency is
adjusted to the most accurate insulation measured value
possible. The measurement signal is affected if it goes
through a rectifier or inverter, and this can lead to phase
errors that may result in an incorrect system leakage
capacitance value.
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