Dielectric response function for nonhomogeneous insulations

Dielectric response function f(t) of an insulation allows its behavior estimation in any electric field, constant or time variable. Generally, for the f(t) computation, a DC voltage U₀ is applied, for a long enough period of time, on the insulation and the resorption (depolarization) current i_r (t) is measured. In the present paper, the dielectric response function is determined based on its Fourier transform, taking into account the frequency variation curve of real part of complex permittivity. Thus, the time variation curve of resorption currents and frequency variation curve of real part of complex permittivity have been determined and, based on them, the dielectric response function has been calculated for two different kinds of samples, mineral oil impregnated paper and water treed polyethylene. Finally, the time variation curves of f(t) obtained with both methods are analyzed.