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2.5
Selection of the surge voltage
The selection of the surge voltage depends both an the test
voltage of the faulty cable and an the ignition behaviour of the
fault. The ignition behaviour is governed not only by the
voltage level, but also by the duration of the surge impulse.
The latter again mainly depends on how the Impulse
capacitors are connected.
In practice, 2,5 or 4 kV are recommended for low voltage
cables. In the event of medium or high voltage cables, it might
be necessary to determine the surge voltage to be set by trial.
In this case one should always start with the lowest voltage of
2,5 kV.
Surge impulses which do not cause a flashover are reflected at
the cable end, whereby their impulse voltage is doubled. This
fact is to be taken into account as laid down by VDE 0298.
2.6
Safety terms as per VDE 0104
2.6.1 Ready for mains connection
Indicated by a white pilot lamp (6).
Mains voltage is connected.
Instrument is not on.
2.6.2 Ready for operation
Indicated by a green pilot lamp (7).
Instrument is on.
No high voltage.
Output earthed.
5
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