Bender EDS460-DG, Руководство по эксплуатации

Страница: 18 / 76

System description
18 TGH1429en/10.2008
The following residual currents flow through the measuring current
transformer of the EDS...:
the test current I(ds) caused by the insulation fault R
F-N
,
residual currents I(d) flowing through the system leakage capacitances
C
E-V,
C
E-N,
R
F-V
and R
F-N
,
transient leakage currents caused by switching and control activities in
the system,
Low-frequency leakage currents generated by the use of converters.
3.2.4 Requirements for reliable insulation fault location
The EDS... is intended to detect insulation faults downstream of the
measuring current transformer R
F-N
. For this purpose, the test current
caused by the insulation fault has to be detected reliably. Preconditions
are:
The test current I(ds) exceeds 1.5 mA and is less than 50 mA.
The upstream capacitances C
E-V
must be at least as large as the down-
stream capacitances C
E-N.
The system leakage capacitance must not be too large (see "Response
sensitivity characteristics" on page 65).
The total residual current through the measuring current transformer
(test current and residual currents etc.) must not exceed 2 A.
Not only does the amplitude influence the reliable detection of the test
current but also the residual current frequency. This effect is illustrated
in the following fault curve.