Some equivalent circuits and analytical estimation of the PD parameters
Nikolay V. Kinsht, N. N. Petrunko · 2016
The most important factors influencing the processes of the PD are: the properties of the insulation, picture of the electric field in the core of the transformer, the location of the inclusions as potential defects (its “energy coordinates”), the electrical and physical properties of the potential defects (defect size, breakdown and extinction voltages of the PD, the discharge volt-amps diagram). Report focuses on analytical describing of the PD arising process. There are used both the circuit theory and the theory of electric field. First, permittivity, joule and polarization losses are used as the parameters of the insulation. Second, inclusion charge and area of field distortion are estimated in terms of analytical description of the electric field around inclusion. Further, the equivalent impedance of the environment relative to inclusion seeks in terms of analysis of two electric field modes (breakdown mode and short circuit mode) and with Thévenin theorem. Inclusion during PD time regards as a two-pole circuit element. The impedance together with the inclusion discharge volt-amps diagram are used for formalization of the description of PD current and estimation of the extinction voltage value.