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• Evaluate the effect of different insulator profiles on Flashover Voltage (FOV). • Analyze the risk of the insulators utilization under different ambient conditions. • Effect of different pollutions and humidities variations on the reliability of the aged Silicone Rubber (SiR) insulators. • Reliability of the aged Silicone Rubber (SiR) insulators has been calculated. In this paper, the effect of different pollution and humidity variations on the reliability of aged Silicone Rubber (SiR) insulators are investigated. Firstly, four different types of 20 kV SiR insulators have been selected to evaluate the effect of different insulator profiles on Flashover Voltage (FOV). Then artificially accelerated aging tests with 1000 h duration have been conducted for the aging of insulators. Numerous FOV tests have been carried out on the aged SiR insulators under different humidity and pollutions. Next, the risk of insulators utilization under different ambient conditions have been calculated by using the experimental test's data. Finally, the reliability of insulators under different conditions have been calculated and a new mathematical model for the reliability in different humidity has been proposed. The effect of SiR insulator profiles on FOV has been studied and the results have been shown that lower FOV is related to insulators with thicker profiles as well. [ABSTRACT FROM AUTHOR]

• A dynamic theoretical model is proposed for AC flashover under pollution condition. • It calculates flashover parameters for the fan-shaped non-uniformly degrees. • The experimental tests are performed on the sample insulator to validate model. • With increasing non-uniformly degrees, the critical flashover voltage decreases. • Using experimental results, the propoer insulation level is selected for a sample system. The geometry of fan-shaped pollution on the surface of an insulator accounts for two different values of Salt Deposit Density (SDD), conductivity, and resistance on the leeward and windward sides of the insulator. This paper proposes a novel dynamic theory model of AC flashover based on equivalent resistance in the presence of a fan-shaped pollution layer. The proposed model can calculate flashover parameters for different values of the fan-shaped pollution density degree (T) and extension degree (J) considering instantaneous variables in arc progression. In this model, the arc current is formulated using the arc equivalent circuit for a constant arc voltage in terms of arc length propagation. Also, the Form Factor (F) is defined as a function of the arc length by sampling from the desired insulator and curve fitting. To validate the analytical model, some experiments are performed on an insulator unit of suspension porcelain by applying artificial pollution at three levels: light, medium, and heavy. Test results show that the critical flashover voltage (CFO) is reduced by 19% by varying J from 1 (uniform pollution) to 1/15. Moreover, by varying T from 10% to 30%, the CFO decreases by 9%. As the non-uniformity degree increases, the correction factor varies in the range of 0.798 ~ 0.938. The proposed modeling of flashover provided by the paper could be used to perform a dimensioning method on insulators under fan-shaped pollution conditions. Also, the proposed model can be included in the EMTP-type platforms to determine the minimum insulator flashover characteristic that will provide an adequate flashover performance under pollution conditions. [ABSTRACT FROM AUTHOR]