Multifractal analysis on polarisation and depolarisation current of the transformer insulation

In this paper multifractal nature of polarisation (pol) and depolarisation (depol) current of a transformer insulation is identified and shown using a multifractal spectra. Multifractal analysis is carried out on pol and depol current of oil-impregnated pressboard samples of different moisture contents. Multifractal analysis is also carried out for pol and depol current of a transformer before and after oil reclamation. It is shown using multifractal spectra that pol and depol current of transformer insulation are fractal and scales with time. The sandbox method is used in this work to determine multifractal spectrum of pol and depol current for the moment order q = -10 to q = 10, and application of sandbox method to determine multifractal spectrum of pol and depol current is demonstrated.