Megger INGVAR, User Manual

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46 ZP-BH05E BH0654BE
7 HOW TO USE INGVAR
Rules of thumb
▪
a) Distance max. 0.5 m, current 5 kA
(For example Low Voltage Circuit Breaker testing)
Minimise cable impedance. Weight is a minor problem.
Use cable set with many cables in parallel or bars.
▪
b) Distance 5 meters or more, current max 3 kA and time
max. 10 seconds:
(For instance at outdoors Current Transformer testing)
Since current is moderate and load time is short, it is
possible to use a cable set that is not too clumsy. One or
two cables in parallel each side is sufficient in many cases,
especially if it is possible to twist the cables.
▪
c) Distance 5 meters or more and current > 3 kA:
(for instance outdoor Current Transformer testing)
Low impedance must be given highest priority in order
to get the desired current. This means many cables in
parallel. Unfortunately it is unavoidable that the cable set
will become rather heavy.
▪
d) Continuous or long injection time.
(for instance at heat run)
First you must check that cable set has sufficient number
of cables that current through a single cable does not
become too high.