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The V-I characteristic of ZnO varistor which has been obtained from experimental test, is an important parameter to model surge arrester electrical behavior. Generally, in grid voltage, this characteristic depends on temperature variations. In this paper, an improved metal oxide surge arrester electrical model has been proposed under grid voltage. Temperature effects on surge arrester performance have been considered in the proposed model. Artificial neural network has been used to determine V-I characteristic at temperature variations. Therefore, in proposed model, the V-I characteristic of each varistor has been estimated based on applied voltage and operating temperature. To validate proposed model, laboratory setup and infrared thermal camera have been arranged and experimental tests results have been compared with simulation ones. Results revealed that there has been a good agreement between simulation and experimental results. Moreover, electrical behavior of surge arrester is predictable with high precision through the proposed artificial model. [ABSTRACT FROM AUTHOR]

The most monitoring techniques of metal oxide surge arresters are based on harmonics analysis of resistive leakage current. Therefore, the extraction of resistive component from total leakage current is required. Up to now, several methods have been proposed for resistive leakage current extraction such as time-delay addition method. This method is only able to separate accurate resistive component under pure sinusoidal applied voltage. An improved time-delay addition method is proposed in this paper which is able to extract surge arrester resistive component under applied harmonic voltage. To accomplish this purpose, experimental tests have been performed on 20 kV surge arrester and obtained voltage and leakage current signals have been applied to the proposed and previous algorithms for resistive component extraction. In addition to investigate the ability of proposed algorithm, a typical surge arrester has been simulated in ATP-EMTP software and total leakage currents have been applied to both algorithms for resistive leakage current extraction. Results show that the proposed method is able to extract resistive component under applied harmonic voltage more accurate than previous one. Therefore, it is an improvement with respect to previous one that only works for sinusoidal voltage. [ABSTRACT FROM AUTHOR]

Metal oxide surge arresters are important equipments that apply to power system for protection against switching and lightning over-voltages. Surge arrester monitoring technique based on leakage current analysis is a conventional monitoring method. Lack of proper features and thresholds is most important limitation of this method. In this paper, new monitoring indexes for surge arrester diagnostic are proposed to determine surge arrester condition under different situations including clean condition, surface contamination and ultraviolet aging. The experimental tests have been performed on polymer surge arresters to evaluate the ability of the proposed indexes for distinguishing the operating condition of surge arresters. Results have been shown the viability of the new indexes on surge arrester monitoring procedures. The investigation and the discussion of the produced results can give good ideas the electric engineers in order to easily analyze arresters’ condition leading to effective schedule maintenance. [ABSTRACT FROM AUTHOR]

• Leakage current magnitude decreases under longitudinal non-uniform pollution. • Leakage current magnitude increases with increasing the aging time and humidity. • Phase angle of leakage current is analysed based on the insulator pollution level. • The non-uniformity of pollution distribution has little effect on the phase angle. • Increase of humidity leads to a slight decrease in the phase angle. This paper presents the comprehensive analysis of Leakage Current (LC) of a silicone rubber insulator under uniform and longitudinal non-uniform pollution conditions based on a large amount of test data. The experimental tests are carried out under different humidity levels for un-aged and aged samples. The results obtained indicate that the LC harmonics magnitudes increase with increasing the salt deposit density, aging time, and humidity, while they decrease with increasing the pollution non-uniformity degree. The analysis of phase angle difference between LC and applied voltage (θ I - V °) demonstrates that the θ I - V ° is in the range of 54.3°–60.4°, 20.1°–32.5°, and 7.5°–11.8° under clean condition, light pollution and moderate pollution conditions, respectively. In addition, the θ I - V ° is less than 2.3° under heavy pollution condition. The non-uniformity of pollution distribution and insulator aging time have very little effect on the θ I - V ° , while the increase of humidity leads to a slight decrease in the θ I - V °. [ABSTRACT FROM AUTHOR]