Installation and Commissioning
8-537SA6 Manual
C53000-G1176-C133-1
q
Isolate the line and earth it on both ends. During the whole testing procedure the
line must be open at the remote end.
q
Make a test connection between a
single phase
and ground. On overhead lines it
can be connected anywhere, however, it must be located behind the current
transformers (looking from the busbar of the feeder to be checked). Cables are
earthed on the remote end (sealing end).
q
Remove the protective earthing of the line.
q
Connect a circuit breaker to the line end that is to be checked.
q
Check the direction indication (LED if allocated)
q
The faulty phase (FNo for L1 or for L2 or for L3) and the direction
of the line, i.e. “6HQV())RUZDUG” (FNo ) must be displayed in the earth fault
protocol (see also Section 7.1.1.4).
q
The active and reactive components of the earth current are also displayed. The
reactive current (“,VHQ5 ”, FNo ) is the most relevant for isolated systems,
for resonant-earthed systems it is the active current (“,VHQ$ ”, FNo ). If the
display shows the message “6HQV()5HYHUVH” (FNo ), either the current or
voltage transformer terminals are swopped in the neutral path. In case the message
“6HQV()XQGHI'LU” (FNo ) appears the earth current may be too low.
q
Deenergize and earth the line.
The check is then finished.
8.3.10 Polarity Check for the Current Measuring Input I
4
If the standard connection of the device is used whereby the current measuring input
I
4
is connected in the star-point of the set of current transformers (refer also to the
connection circuit diagram in the Appendix, Figure A-9), then the correct polarity of the
earth current path in general will result automatically.
If however the current I
4
is derived from a separate summation CT (e.g. a core balance
CT) or from a different point of measurement, e.g. transformer star-point current or
earth current of a parallel line, an additional polarity check with this current is
necessary.
If the device is provided with the sensitive current measuring input I
4
and it is
connected to an isolated or resonant-grounded system, the polarity check for I
4
was
already carried out with the earth fault check according to 8.3.9. Then this Subsection
8.3.10 can be ignored.
Otherwise the test is done with a disconnected trip circuit and primary load current. It
must be noted that during all simulations that do not exactly correspond with situations
that may occur in practice, the non-symmetry of measured values may cause the
measured value monitoring to pick up. This must therefore be ignored during such
tests.
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