AC flashover dynamic theoretical and experimental model under fan-shaped and longitudinal pollution on silicone rubber insulator

Due to wind and uneven distribution of the field along the insulator, a kind of non-uniform contamination is deposited on the insulator surface as fan-shaped and longitudinal pollution. This paper investigates such non-uniform pollution from theoretical and experimental points of view. For this aim, the residual resistance of the pollution layer is formulated based on the geometry of fan-shaped and longitudinal non-uniform pollution. Also, the arc current is formulated using the arc Obenaus's equivalent circuit for a constant arc voltage in terms of arc length propagation. Finally, the AC dynamic theoretical model of pollution flashover is proposed that can estimate flashover parameters for different values of the fan-shaped density degree (J), extension degree (K) and longitudinal non-uniform pollution density degree (Z) considering instantaneous variables in arc progression. It results that with increasing Z, the flashover voltage increases, while by increasing the J and K, the flashover voltage decreases. To validate this model, the experimental tests are performed on the sample silicone rubber (SiR) insulator that show acceptable accuracy of theoretical model. Furthermore, based on experimental results, a new correction coefficient is proposed under fan-shaped and longitudinal pollution that varies in the range of 0.85-1.62.