A special feature of importance of the d.c. test is the testing of cables which are expected to operate under a.c.
conditions. If the tests are done under a.c. conditions, a high charging current would be drawn and the
transformer used would have to have a current rating. It is thus normal to subject the cable (soon after laying it,
but before energising it ) to carry out a high voltage test under d.c. conditions. The test voltage would be about 2
(working voltage ) and the voltage is maintained from 15 min to 1.5 hrs. This d.c test is not complete equivalent
to the corresponding a.c. conditions , it is the leakage resistance which would determine the voltage distribution,
while in the a.c. conditions, it is the layers of different dielectrics that determine the voltage distribution in the
cable. Although the electric field differs in the 2 cases, it is likely that the cable will stand up to the required a.c.
voltage.