Power cable sheath test

[salem]

33 kV cable, 10 km length being laid in sections of 500 m,and in order to control the test results, for each section the cable sheath is tested and another sheath test is done after jointing each section and finally a sheath test is done for the hall cable length with joints and terminations.
The test voltage used is 10 kV. Is this repeated process of testing will affect the cable (any damage or deterioration)

 

[ausphil]

Salem,

As long as the sheath is designed to handle this test voltage, there is no issue. IEC 60229 gives the site test voltage levels for certain sheath thicknesses - 4kV/mm. Note that the routine test in the factory before it gets shipped to site is 8kV/mm.

Some companies reduce the test voltage after commissioning for their routine maintenance tests, so using a reduced test voltage is an option if you feel uncomfortable retesting at 10kV.

I applaud you for doing it this way, because you can greatly reduce fault location times and accuracy if their is a problem. Also, you can rectify the problems prior to closing up the roads at joint bays, which pays for itself after finding one problem.

As for the question of loss of life of the insulation, all electrical stress ages insulation. By performing HV tests on the insulation, you may shorten its life by a matter of hours or days, which over the operating life of the asset will not be seen. The positives of this method far outweigh the negatives (more stress on the sheath insulation, more testing time,). We perform the testing and fault locating function, and finding sheath faults is very much easier, faster and more accurate in 500m lengths than 10km lengths.

ausphil