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19. CABLE TESTING
Cable testing and locating cable faults are preformed in
three ways:
1. Directly on the testing points if they are fitted on the unit.
2.1 Directly on the cable connectors with the cable connected
to the switchgear.
2.2 Cable connector dismounted from the switchgear.
CAUTION
Cable testing must be carried out in accordance
with the cable manufacturer’s recommended
practice.
DANGER
Remember that the cable has two ends. Both ends
of the cable need to be isolated. This is typically
done by opening the disconnectors of SafeRing
SafePlus switchgears connected to the cable. The
free end of the tested cable needs to be secured
against accidental access.
CAUTION
Sometimes cable testing through the busbar of the
switchgear is preferred. This way several sections
of cable can be tested at the same time. This is
feasable, but remember the following limitations:
− DC and VLF voltages must not be applied to
voltage transformers and surge arresters.
19.1 PROCEDURE FOR SWITCHGEAR WITH TEST
POINTS
1. Open switch disconnector.
2. Check voltage status.
3. If voltage is not present, close the earthing switch.
4. Connect the testing equipment on top of the testing points
which hold the earth bar (B).
5. Remove the earth triangle and perform the test. Respect
maximum test voltage levels as detailed in table below.
Recommended test values can be applied with busbars
energized.
6. Refit the earth triangle. Tightening torque: 25 Nm.
Maximum cable test voltages when testing cables using the cable test points of the switchgear
Rated voltage of the switchgear Ur (kV rms) 12kV 17,5kV 24kV Time
Power frequency cable test voltage Uct(ac) (kV rms) 12kV 17,5kV 24kV 15 min.
DC cable test voltage Uct(dc) (kV peak) 24kV 34,8kV 40kV 15 min.
VLF cable test voltage (Sine-wave, 0,1Hz) Uct(VLF) (kV rms) 18kV 26,1kV 28kV 15 min.
VLF cable test voltage (Cosine-rectangular, 0,1Hz Uct(VLF) (kV peak) 25,5kV 36,9kV 40kV 15 min.
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