7.1.6
Special Features for Tests of Calculated Ground (Earth)
Overcurrent
Functional Description
Depending on the WIC1 settings, the ground (earth) current can be calculated instead of
being measured. Then it is established from the geometrical amount of the three phase
current values, more or less a numerical Holmgreen. If, for instant, a single-phase test
current is impressed, the measuring value (tripping value) in the ground (earth) current
path equals the current in the tested phase. If, with a phase shift of 120° a three-phase test
current is impressed, the measuring value in the ground (earth) current path equals zero.
Requirement for the Test System
The WIC1 is powered by the phase CTs. In order to guarantee a reliable tripping a minimal
current has to ow, see ╚═▷ “9.1.6 Power Supply”. If the setting of the ground overcurrent
threshold IG> is lower than the smallest possible 1-phase supply via the phase CTs, then
the ground current tripping can only be tested by a three-phase current source. Only if the
set ground overcurrent threshold is higher than the smallest possible 1-phase supply via the
phase CTs, then the test can be performed with a single-phase current source.
197WIC1WIC1-1.0-EN-MAN
7 Commissioning
7.1.6 Special Features for Tests of Calculated Ground (Earth) Overcurrent
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