Measuring voltage response:: a non-destructive diagnostic test method of HV insulation

In insulation materials several chemical and physical deterioration processes arise, such as thermal and electrical ageing, and moistening, due to operational and environmental stresses. As well as electrical strength, these deterioration processes influence the dielectric processes, the conduction and the polarisation of the insulation. The dielectric strength of insulation cannot be determined without destroying it, but the intensities of dielectric processes can be investigated by non-destructive diagnostic test methods. Consequently, by diagnostic tests the ageing state of the insulation, i.e. the probable decrease in its electrical strength, can be detected without damaging it. By using the voltage response method for diagnostic testing of electrical insulation its condition can be easily determined, i.e. the probable decrease of the dielectric strength and the reliability of the insulation can be indirectly inferred. By testing cables with impregnated paper insulation the two main deterioration processes, i.e. thermal ageing and moistening, can also be distinguished.