Application of Analytical Modeling of Flashover Derived for Flat Samples to Polluted 11-kV SiR Insulators

This article introduces a complementary criterion for flashover (FOV) of polluted insulators based on the concept of equivalent impedance variation with discharge length and leakage current. An analytical electrothermal model enabling the calculation of critical FOV voltage and critical current of polluted insulators is developed using this complementary criterion and the equivalent impedance criterion. It is shown that the critical parameters depend on the thermal characteristic of the discharge and the components of the equivalent electrical circuit. The comparison of the computed FOV voltage and critical current is in good accordance with the experimental ones for a laboratory insulation flat sample model with different applied voltage waveforms. The application of the developed model to actual insulators destined for 11-kV systems, by including equivalent salt density deposit (ESDD) and the form factor, shows that FOV voltage values match very well with the experimental data in clean fog test conditions.