High voltage insulation assessment using pulse analysis

The use of applied DC voltages to determine the response of dielectric materials in the time domain over extended periods of time is well known. Transformation to the frequency domain enables the presentation of the data in the form of the permittivity and the dielectric loss to be shown as functions of frequency of the applied electric stress. Dielectric materials deteriorate (age) with time when subjected to multifactor stresses. These stresses can be temperature, electric stress, mechanical stress and environmental factors resulting in chemical processes. The extent of ageing is of concern since most ageing processes result in a reduction in dielectric strength and residual life. Thus a method of nondestructive monitoring of the dielectric would be of considerable advantage. It is the purpose of this paper to investigate the dielectric behaviour of polyethylene subjected to an ageing process