A Generalized Probability Mass Function for Partial Discharge Electron Avalanche

Equipment and electric machinery working under a high voltage stress, are at risk of an insulation failure. Usually, insulation failure processes start with inception of a Partial Discharge (PD) which generates PD signals. Monitoring of PD signals can prove aging of the insulation and the gradual deterioration of the solid dielectric. There are different methods for estimation of the charge involved in the PDs phenomena to be used for determination of insulation deterioration level. Some of them are based on application of an impedance for apparent charge determination (conventional methods, presented in IEC60270 standard) and the others are based on wireless measurement of the high frequency induced PD signal in an antenna as a non-conventional method, presented in IEC62478 standard. For PD estimation through non-conventional methods, it is necessary to have a proper probability mass function for number of electrons in the electron avalanche. In this paper, a general numerical method will be introduced for determination of this function in an arbitrary environmental condition, i.e., under a specific electric field intensity, a specific pressure, and a specific temperature. This method can be later employed for PD calibration when using non-conventional PD measurement method.