Product Description; Functional Description - Bender ISOMETER iso1685DP-425 Manual

Function

3.2 Product description

ISOMETER®s of the isoxx1685Dx-x25 device family are used for insulation monitoring of large
systems designed as IT systems. The device variants described in the manual have different
voltage ranges. The exact device specification can be found in Chapter 12. Technical data.
The measurement method especially developed for this purpose monitors the insulation re-
sistance even in installations where extremely high system leakage capacitances against earth
exist due to interference suppression methods. Adaptation even to system-related high leaka-
ge capacitances is automatic.
The ISOMETER®s isoxx1685DP-x25 generate locating current pulses required for insulation
fault location. That allows the localisation of the insulation fault using permanently installed
or mobile insulation fault locators.

3.3 Functional description

Insulation monitoring is carried out using an active measuring pulse which is superimposed
onto the IT system to earth via the integrated coupling. If the insulation resistance between
the IT system and earth falls below the set prewarning response value R , the "ALARM 1" LED
an1
lights up and relay K1 (11/12/14) switches. If the insulation resistance falls below the alarm re-
sponse value R , alarm relay K2 (21/22/24) switches and the "ALARM 2" LED lights up.
an2
When starting the insulation fault location, the "PGH ON" LED signals the locating current pul-
se.
3.3.1 Insulation monitoring
For insulation monitoring, a pulsating AC measuring voltage is superimposed onto the IT sys-
tem. The measuring pulse consists of positive and negative rectangular impulses of the same
amplitude. The period duration depends on the system leakage capacitances in each case and
the insulation resistances of the system to be monitored.
U
m
t
Pulse sequence of the measuring voltage for insulation fault monitoring
An insulation fault between the IT system and earth closes the measuring circuit. If the insula-
tion resistance between system and earth falls below the set response values R and R (re-
an1 an2
sponse value R can be set equal or higher than R ), the associated alarm relays K1 (11, 12,
an1 an2
14) or K2 (21, 22, 24) switch. Detected insulation faults are signalled to other bus devices via
the BMS bus. In addition, the alarm LEDs ALARM 1 or ALARM 2 light up.
14 isoxx1685Dx-x25_D00272_07_M_XXEN/09.2022