System description
14
EDS460-490_D00085_01_M_XXEN/02.2016
3.2 Function of the EDS system
When an insulation fault is detected by the insulation monitoring device in
the IT system, the insulation fault location process will be started.
On the occurrence of a first insulation fault, a fault current essentially determi-
ned by the system leakage capacitances flows in the IT system. The funda-
mental idea in fault location is therefore to close the fault current loop for a
short period via a defined resistance. As a result of this principle, the system
voltage itself drives a locating current containing a signal that can be evalua-
ted.
The locating current signals are generated periodically by the IRDH575 res-
pectively the PGH… . The locating current is limited in amplitude and time. As
this happens, the system conductors are connected alternately to earth via a
defined resistance. The locating current generated in this manner depends on
the magnitude of the present insulation fault and the system voltage. It is li-
mited according to the setting of the IRDH575 respectively the PGH… . For pl-
anning purposes, it should be noted that no system components are present
in which this locating current can bring about a damaging reaction, even in
unfavourable cases.
The locating current pulse flows from the locating current injector via the live
parts, taking the shortest path to the location of the insulation fault. From the-
re, it flows via the insulation fault and the PE back to the IRDH575 respectively
PGH… . This locating current pulse is then detected by the measuring current
transformers located in the insulation fault path, and is signalled by the con-
nected insulation fault locator.
Additional information is available in the data sheet "Technical issues affec-
ting the use of insulation fault location systems".
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