Testing Procedures; Finding Sources Of Excessive Leakage Current - METREL A1472 User Manual

A 1472, A1579

4.3 Testing procedures

4.3.1 Finding sources of excessive leakage current

The described testing procedure in this chapter is applicable for
troubleshooting in the installation and electrical equipment in case of
nuisance tripping of protective devices.
1. Embrace all active conductors (L and N, L1 and L2 and L3, L1 and
L2 and L3 and N) at the origin of installation.
The advantage of using the differential method is that all leakage
currents downstream the point of measurement will be captured.
The same leakage as "seen" by the RCD is measured.
Alternatively, if the main protective conductor at the origin of
installation.is accessible the direct measurement can be used.
If measuring currents through PE conductors it is possible that a
part of the leakage currents will not be measured as they are flowing
through different parallel paths. Refer to METRELs handbook Guide
for testing and verification of low voltage installations for more
information about parallel paths.
2. All suspicious loads should be connected. If the leakage current lies
inside expected limits try to run the suspicious loads in different
operation modes and find out if any of them is problematic. Use
MAX, PEAK, LOGGING functions on the measuring equipment if
available.
3. If the leakage current is too high try to isolate the fault downstream
of the installation. This can be done by disconnection of individual
parts of the installation as shown on Fig. 7 - sub distribution boards,
fuses, switches, appliances etc. When the faulty part is
disconnected the leakage current value will drop or fall to zero.
4. Sometimes it is not allowed to disconnect the mains voltage. In this
case additional measurements (direct or differential) should be
carried out downstream of the installation's input as shown on Fig.
8. By doing this the measured leakage currents will be limited to a
smaller part of the installation.
Leakage current clamp
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