Chauvin Arnoux C.A 6456 Notice De Fonctionnement page 66

Case of an installation with a TN type neutral situation (selective measurement) :
=> Connect the mains socket (or the
3 separate cables) to the installation
to be tested,
=> Connect a current probe to the terminal
and encircle the earth of which the
resistance is to be measured: the current
used to calculate Z is that measured
E SEL
by the probe,
=> Plant the auxiliary rod PE as close as
possible to the earth electrode to be
measured for a measurement that is as
accurate as possible,
=> Compensate the cables.
Note : without the current probe, what is measured is the global earth of the network, which is not very
significant.
Case of an installation with an IT type neutral situation (not isolated) :
Preliminary remarks :
- the power supply transformer of the installation must not be completely isolated, but earthed through an
impedance,
- the installation must also not be in first fault: start by checking the indication of the Permanent
Insulation Tester concerned,
- the "grounds to earth" R and the earth of the power supply transformer must be separate to allow the
E
circulation of the measuring current.
=> Connect the mains socket (or the
3 separate cables) to the installation to
be tested,
=> Plant the auxiliary rod at a distance
> 25 m from the earth electrode.
4.3.3 MEASUREMENT PROCEDURE
The instrument first checks the resistance of the rod and measures the voltage between PE and earth, then
measures the voltages U , U
LN LPE
If these values are correct, pressing the TEST key starts the measurement.
Remark : to be sure that the auxiliary rod is located in a zone not influence by other earth electrodes, move
the rod ( 10% of the distance and repeat the measurement. The result must not change. If it does, move the
rod until the earth measurement remains unchanged.
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, U .
NPE
65