Prediction of PD Magnitudes using Three-Dimensional Finite Element Analysis

The use of 2D finite element analysis (FEA) to predict PD magnitudes for ellipsoidal and spheroidal cavities has been demonstrated for well over a decade. However the introduction of an arbitrary defect, such as a track along an interface, converts even an axisymmetric 2D geometry to 3D, and prediction of PD from such arbitrary defects was not possible prior to the practicability of routine 3D FEA. We have used 3D finite element analysis to model a separable connector with a track along various interfaces, which facilitates computation of the PD magnitude as a function of track length and position along the interface. The PD magnitude is estimated by calculating the change in capacitance which occurs when the defect goes from nonconducting to conducting and multiplying by the partial discharge extinction voltage. Our predictions on this basis are in good agreement with measurements.