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This study aims to predict the flashover voltage (FOV) of silicone rubber (SiR) insulators. Accordingly, it benefits from two methods, including an artificial neural network (ANN) model and a FOV gradient fitting model. The FOV and leakage current (LC) tests are carried out on one un‐aged and three aged specimens under uniform and longitudinal non‐uniform pollution circumstances. The proposed ANN model is designed based on equivalent salt deposit density (ESDD), pollution non‐uniformity degree, aging time, LC first harmonic magnitude I1, and total harmonic distortion. Furthermore, a FOV gradient model is proposed based on ESDD, I1, and creepage distance. To validate the proposed models, the FOV and LC tests are conducted on two different types of SiR insulators. Then, the predicted FOV from the ANN model and calculated FOV from the voltage gradient model are obtained. The results indicate that the relative errors of the ANN model and FOV gradient fitting model are <6.4 and 7.3%, respectively. [ABSTRACT FROM AUTHOR]

The current distribution, ampacity and magnetic field of parallel power cables are calculated. The calculations are performed in both sinusoidal and harmonic current profiles. The simulations are conducted on the underground medium voltage cables with metallic sheaths. The effects of single‐point bonding and solid bonding of sheaths grounding system are evaluated. In this study, cables are installed in flat formation with three cables in each phase and the effect of different distances between cables on the parallel cables parameters is studied. Computations are conducted for all possible arrangements of parallel cables and the worst and the best arrangements from the point of balancing current division, maximum ampacity and minimum magnetic field are presented. Furthermore, the effects of placing parallel cables in one row or two rows above each other are investigated. Calculations of current distribution and magnetic field are performed using the sub‐conductors method that considers the skin and proximity effects. Finite element method thermal simulations are excited to determine the power cable ampacity in different configurations. Experimental tests on parallel cables in both single‐point bonding and solid bonding systems are carried out and the results verify the accuracy of simulations. [ABSTRACT FROM AUTHOR]

Metal-oxide surge arresters are one of the most important equipments for power system protection against switching and lightning over-voltages. Surge arresters leakage currents increase by the operating time. In this study, the important factors on leakage current variations such as surface contamination, ultraviolet ageing and varistor degradation have been studied. To accomplish this purpose, experimental tests have been performed on various polymer housed surge arresters. Fast Fourier transform analysis has been performed on measured leakage currents. Results show that ultraviolet radiation and varistor degradation affect resistive harmonic components, especially the third and fifth harmonics. Moreover, it is observed that surface contamination has influence on fundamental harmonic variation more than ultraviolet ageing. In addition, combination of ultraviolet radiation and pollution had more effect on leakage currents. The investigation and the discussion of the results can be used to easily analyse arresters condition leading to effective schedule maintenance. [ABSTRACT FROM AUTHOR]

Metal‐oxide surge arresters are one of the most important equipments for power system protection against switching and lightning over‐voltages. Surge arresters leakage currents increase by the operating time. In this study, the important factors on leakage current variations such as surface contamination, ultraviolet ageing and varistor degradation have been studied. To accomplish this purpose, experimental tests have been performed on various polymer housed surge arresters. Fast Fourier transform analysis has been performed on measured leakage currents. Results show that ultraviolet radiation and varistor degradation affect resistive harmonic components, especially the third and fifth harmonics. Moreover, it is observed that surface contamination has influence on fundamental harmonic variation more than ultraviolet ageing. In addition, combination of ultraviolet radiation and pollution had more effect on leakage currents. The investigation and the discussion of the results can be used to easily analyse arresters condition leading to effective schedule maintenance. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]