ZENER 8000-V Installation Manual
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18
IM00165
Magnitude of capacitive leakage currents
The magnitude of an AC current can be evaluated according to several different concepts. The appropriate
choice is dictated by the intended application of the result (ie what it is that you want to know). Some of the
possible methods and typical purposes are:
Concept / Method
Purpose
Notes
RMS
True RMS value
Heating effect of the
current
This method widely applied by
default for AC current
measurement. It is not always
the relevant interpretation!
RMS(300Hz LP)
True RMS value of
the current after a
300Hz low-pass
filter is applied
Approximation of the
response of some earth
leakage detectors/relays
Some earth leakage current
relays incorporate a filter to
reject high frequencies in order
to reduce nuisance tripping
Ipk
Instantaneous peak
value of the
leakage current
Possible consideration of
the potential to overload
the input circuitry of
instrumentation or disrupt
operation in other ways
Depends on the design detail of
the instrumentation involved.
The characteristics of earth leakage monitoring devices are closely specified in the relevant technical standards.
In most instances, these standards consider leakage currents at 50/60Hz and leave the behaviour at higher
frequencies such as a few kHz unspecified. The design of some, but certainly not all of these devices
incorporates filtering to reduce sensitivity to frequencies higher than 200…300Hz in order to reduce the
likelihood of nuisance tripping. The RMS(300Hz LP) evaluation concept is intended to reproduce this
Note that all of the
capacitors in this
diagram are just
“stray” capacitances
incidental to cables,
motors etc.
There are no
intentionally installed
capacitors here.
Single line diagram showing potential paths for capacitive leakage currents
