Experimental research of the correlation between partial discharges in polyethylene insulation and fractal characteristics of causing them treeing

The following correlations between partial discharge (PD) distributions and fractal characteristics of calling them dendrites are revealed in an outcome of the experimental researches reported. Asymmetrical distribution effect on the positive and the negative half-wave of the applied voltage distributions of frequencies of phases of PD appearances with smoothed tops are intrinsic to a bushing-like treeing. The distributions of frequencies of phases of PD appearance on the negative and the positive half-wave of the applied voltage are similar to a treeing-like dendrites with low fractal dimension: they are positively asymmetric and weakly pointed. It is observed, that lengthwise growth of a bush-Eke dendrite decelerates or ceases, an average PD quantity during a period decreases, a diameter of branches thickens from 1-3 micron to 6-10 micron at various magnitudes of the applied voltage. This phenomenon is connected with different character of electric field strength distribution at a treeing-like and a bush-like form of a dendrite and accordingly with different coefficients of electrical field heterogeneity.