• Energy Research

A surge arrester is modeled as a simplified electrical circuit in power frequency applied voltage that consists of a capacitance branch in parallel with a nonlinear resistor. Under applied harmonic voltage, the obtained resistive current of the simplified model exhibits some deficiency, especially in its harmonic contents. This paper presents a harmonic model for metal-oxide surge arresters that can be utilized to simulate their performances under applied harmonic voltage. It has three parallel RC branches to simulate fundamental, third and fifth harmonics contents of total leakage current. Proposed and conventional models have been simulated under different applied harmonic voltages to show the capability of the proposed model. Also, real voltage and leakage current signals, which have been measured experimentally from a 20 kV metal-oxide surge arrester, have been compared with simulation results. Results show that the proposed model can simulate the performance of metal-oxide surge arresters more accurately than the conventional ones under applied harmonic voltages.

Purpose This paper aims to focus on the inclusion of the frequency behavior of grounding system effect on surge arrester (SA) model parameters’ estimation. Design/methodology/approach The grounding system impedance and its frequency behavior are the factors that have influence on the SA performance. Up to now, the grounding system impedance effect and the frequency behavior of the soil parameters have not been studied for the estimation of the parameters of the SA frequency-dependent model. In this paper, the grounding system’s influence on the SA dynamic model has been simulated for rod- and counterpoise-shaped electrodes. Particle swarm optimization with a grey wolf optimization algorithm has been implemented as an optimization algorithm to adjust the parameters of the SA dynamic model. Findings The results show that the frequency behavior of the grounding impedance and soil electrical parameters can impress the optimum parameters of the SA frequency-dependent model and should be considered for more reliable results. Also, the results evidence that the proposed optimization method provides more accurate results compared to other optimization methods. Originality/value To the best of the authors’ knowledge, this work is one of the first attempts to investigate the effect of frequency grounding system on SA frequency-dependent model parameters.

Metal oxide surge arresters are one of the most important equipment for power system protection against switching and lightning over-voltages. High-energy stresses and environmental features are the main factors which degrade surge arresters. In order to verify surge arresters good condition, their monitoring is necessary. The majority of surge arrester monitoring techniques is based on total leakage current decomposition of their capacitive and resistive components. This paper introduces a new approach based on time-delay addition method to extract the resistive current from the total leakage current without measuring voltage signal. Surge arrester model for calculating leakage current has been performed in ATP–EMTP. In addition, the signal processing has been done using MATLAB software. To show the accuracy of the proposed method, experimental tests have been performed to extract resistive leakage current by the proposed method.

AbstractMetal oxide surge arresters (MOSAs) have been widely used as protective devices against switching and lightning overvoltages in power electrical systems. MOSAs have dynamic characteristics in low‐ and high‐current regions. The unique model of MOSA, which is able to evaluate all the possible operating conditions of power systems, would surely be so complicated. Therefore, by the selection of an operating condition, the appropriate model of MOSA has been created. Many parameters affect MOSA performance in low‐ and high‐current regions. As a result, MOSA's performance under different operating conditions has been investigated by using a MATLAB GUI environment. To make a software environment to simulate MOSA performance in a high voltage laboratory, temperature variations influence on leakage current and its harmonic components under power frequency applied voltages and also the efficacy of impulse parameters variations on MOSA's residual voltage have been investigated. The designed graphical environment has been used by 40 electrical engineering students. The results showed that the use of the graphical environment had a great impact on the concepts' understanding of MOSA's performance.

Abstract 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 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 This paper presents proper indicators for evaluation of the surge arrester condition based on the leakage current analysis. Maximum amplitude of fundamental harmonic of the resistive leakage current (Imr1), maximum amplitude of third harmonic of the resistive leakage current (Imr3) and maximum amplitude of fundamental harmonic of the capacitive leakage current have been used as indicators for surge arrester condition monitoring. The effects of operating voltage fluctuation, third order of voltage harmonic, over-voltage and varistor aging have been investigated to show the ability of introduced indicators for accurate diagnostic of arrester’s conditions. In order to have accurate values of stray capacitors, 3D-FEM has been used. Moreover, surge arrester model for calculating leakage current has been performed in ATP–EMTP. In addition, the signal processing has been done using MATLAB software. This study shows that the introduced indicators are proper criteria for surge arrester condition monitoring.

AbstractService unavailability of transmission lines, due to the direct and indirect lightning strikes, is evaluated as a challenging issue within electric companies. The lightning event can produce dangerous overvoltage, equipment failures, and power supply interruptions. Here, externally gapped line arresters (EGLAs) performances installed on a 63 kV transmission line are modelled using EMTP‐ATP to investigate their capability to withstand current and energy discharged by lightning strokes during back flashover phenomena. Frequency behaviour of the grounding system impedance, first and subsequent lightning current parameters effects on insulators back flashover and lightning flashover failure rate have been considered by Monte‐Carlo method. Then, extensive analysis has been carried out to study the absorbed energy of the EGLA and its expected life. The results show the dependency of failure rate and the EGLA expected life on the soil resistivity and lightning strike parameters. The selected EGLA must be provided sufficient lightning protection to the transmission line based on its absorbed energy capability, the soil and lightning parameters and be complied with the discharge energy capability requirement specified by the utility company.

AbstractThis paper conducts the frequency‐dependent grounding system impact on externally gapped line arresters (EGLAs) operation and their placement effects on the lightning performance of a transmission line (TL). The study involves placing EGLAs at different phases of a 400‐kV double‐circuit TL with two downstream shield wires and selecting the optimal state with fewer back‐flashover incidents. The results show that using a non‐linear grounding system leads to a higher back return current from insulators or EGLAs, resulting in a higher flashover rate compared to the frequency grounding system (FGS). Installing four EGLAs in the middle and upper phases of the TL provides satisfactory lightning protection, and the flashover probability is zero and 4.2% for the FGS and the non‐linear grounding system, respectively. A sensitivity analysis including soil resistor variation, economic analysis, and grounding electrode configuration has been performed that confirms installing downstream shield wires and EGLAs is an effective and economical technique for lightning protection.