Megger PFL22M1500 Series, User Manual

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AVTMPFL22M Rev 1 April 2011
61
A3
Remember !
“It’s your fault if you don’t find the fault”
and
“It’s your Fault if you do”
Typical Fault Locating Strategy
The most important aspect of locating a cable fault is the development of a
strategy that will allow the fault location to be safely and positively identified.
This is achieved by following the Megger “Logical Approach to Fault
Location” See previous flowchart.
1. Use only suitably rated, equipment, making sure that all company and
equipment manufacturers' safety guidelines are followed.
2. Positively identify the faulted cable. Following isolation and
Earthing/Grounding of all of the suspect cables and cores, this can be done
by either using an Insulation Continuity Tester, to determine the condition of
each of the cables and cable cores, or by using a TDR to see if all of the
cores appear to have the same characteristics, i.e. (splices, joins, transformers,
etc., at approximately the same distance.
3. If all circuit elements appear to be equal, determine if the electrical length of
the circuit elements agree with the known physical length of the circuit. If it
does not agree, adjust the TDR propagation velocity accordingly.
4. If the TDR data is inconclusive, use the d.c. (Proof/Dielectric Test) function
to positively identify the faulted phase. Separately bring each phase up to a
test voltage as agreed by “local” conditions or regulations. Note the
breakdown voltage from the faulty phase or phases.
a. After the faulted phase (or phases) has been positively identified,
begin pre-location by engaging the Arc Reflection method and
configuring the MTDR and PFL for Arc Reflection. Apply a test