Use of a mixed-weibull distribution for the identification of PD phenomena

The interaction between partial discharge (PD) phenomena occurring in insulating systems is investigated in this paper. In particular, the recognition of two PD phenomena simultaneously active is approached by means of a 5-parameter additive Weibull distribution. Various shapes of the PD height distribution, obtained from measurements performed on specimens of stator bars and windings of ac rotating machines, are considered. It is shown that the proposed probability function fits well the partial discharge height distributions. By this way the probability distribution relevant to each concurring PD phenomenon can be derived, analyzed and identified. Moreover, the standard average quantities are estimated for each phenomenon.