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Introduction. This study investigates substation failures caused by lightning strikes, which significantly affect operational reliability. Given the random nature of lightning strikes, a robust statistical approach is essential for accurately assessing their effects. Method. The research develops a comprehensive procedure to analyse the random distribution of non-vertical lightning strikes on transmission lines using the Monte Carlo method, a widely recognized statistical simulation technique. The goal of this work is to evaluate the performance of air-insulated substations under various lightning strike scenarios affecting the connected transmission lines. This is assessed in terms of mean time between failures (MTBF), determined by the basic insulation level of the equipment. The study incorporates both vertical and non-vertical strikes to address a critical gap in the literature, offering practical insights to enhance the reliability and safety of air-insulated substations. By considering the angle of lightning strikes, the study improves the accuracy of evaluating lightning performance using precise modelling of system components. Results. MATLAB and EMTP software were used to simulate and analyse the substation’s response to lightning-induced surges at various strike angles. The results are more representative of real-world conditions and reveal that non-vertical lightning strikes significantly reduce MTBF, underscoring the importance of advanced protective measures. Practical value. The findings highlight the necessity of accounting for the angle of lightning strikes when assessing substation reliability. [ABSTRACT FROM AUTHOR]

Introduction. Insulation coordination requires accurate prediction of overvoltages at various points within a substation. Computer simulations of electromagnetic transients in real structures of substations become more precise due to the improvements of used models. Goal. This paper discusses in a first step the use of the modified ZnO arrester dynamic model alongside other substation equipment models, considering electrical phenomena like the corona model for reproducing the stresses that lightning can cause in an air-insulated substation and (method) then conducting a statistical approach based on the Monte Carlo method. The implemented MATLAB/ATP procedure estimates not only the substation Mean Time between Failures (MTBF), but also is used to select surge arresters or substation basic insulation levels (BILs). In this procedure ATP transients program is used to calculate lightning overvoltages and multicore environment for the calculations. Results. The obtained MTBF curves offer guidance for selecting appropriate insulation levels based on specific system requirements and conditions. The obtained results comply well with existing international insulation standards. This valuable approach significantly contributes to the field of lightning protection. References 31, tables 3, figures 10. [ABSTRACT FROM AUTHOR]

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• Surge currents with shorter risetime result in stronger induced coupling of the cable. • Double-ended grounding shield can reduce coupling, especially for high frequencies. • Amplitude Shielding factor exponentially increases with surge current risetime decreasing. Secondary cables are susceptible to lightning surge currents when substation is struck by lightning. Little work has been made to the effects of surge currents in substation secondary cables, particularly the effects of surge current rise time. Six types of simulated lightning surge currents with different rise times, ranging from 5.7 μ s to 25.4 μ s, were injected into the substation grounding grid, and the inductive voltage from core wire to ground and the shield current in the closed loop of the buried secondary cable were measured simultaneously. The inductive coupling characteristics and the effect of rise time on shielding factor (SF) of buried secondary cables were investigated using time-frequency domain method. The results indicate that the surge current with shorter rise time will induce higher core-wire voltage and higher the shield current on the secondary cable. Double-end grounding of the shielding layer can significantly reduce the cable coupling response, especially reduce the high-frequency component of the inductive voltage at 10 to 100 kHz with steeper surge currents. The SF of secondary cable increases exponentially from 1.91 dB to 8.15 dB as the rise time of the lightning surge current decreases. [ABSTRACT FROM AUTHOR]

The article presents the results of the development of new methods aimed at more accurate interval estimate of the experimental values of voltages on grounding devices of substations and circuits in the control cables, that occur when lightning strikes to lightning rods; the abovementioned estimate made it possible to increase the accuracy of the results of the study of lightning noise by 28 %. A more accurate value of interval estimation were achieved by developing a measurement model that takes into account, along with the measured values, different measurement errors and includes the special processing of the measurement results. As a result, the interval of finding the true value of the sought voltage is determined with an accuracy of 95 %. The methods can be applied to the IK-1 and IKP-1 measurement complexes, consisting in the aperiodic pulse generator, the generator of high-frequency pulses and selective voltmeters, respectively. To evaluate the effectiveness of the developed methods series of experimental voltage assessments of grounding devices of ten active high-voltage substation have been fulfilled in accordance with the developed methods and traditional techniques. The evaluation results confirmed the possibility of finding the true values of voltage over a wide range, that ought to be considered in the process of technical diagnostics of lightning protection of substations when the analysis of the measurement results and the development of measures to reduce the effects of lightning are being fulfilled. Also, a comparative analysis of the results of measurements made in accordance with the developed methods and traditional techniques has demonstrated that the true value of the sought voltage may exceed the measured value at an average of 28 %, that ought to be considered in the further analysis of the parameters of lightning protection at the facility and in the development of corrective actions. The developed methods have been tested in surveys of the electromagnettic environment of 27 active high voltage electric substations with a 110 kV outdoor switchgear. The application of the techniques amended the accuracy of the information collected, the correctness of the evaluation of the electromagnetic environment of high-voltage substations with a 110 kV outdoor switchgear, the effectiveness of the developed adequate measures to protect against lightning effects.

Copyright of Electrical Engineering & Electromechanics is the property of National Technical University, Kharkiv Polytechnic Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A thin-wire model of conductors with arbitrary cross sections for a finite-difference time-domain (FDTD) method is proposed for the study of lightning transients in electrical systems. The proposed thin-wire model considers both the frequency-dependent characteristics of the wires and the influences of the surrounding media. The model represents a wire using four FDTD cells with an equivalent side length and modified material parameters. A rational equivalent circuit is added at the center edge of the FDTD cells to represent the internal impedance of the wire. An analytical formula for determining the equivalent side length and the modified material parameters of the FDTD cells are also presented. The proposed formula gives a new prospect to build the thin-wire model in FDTD. In this model, the equivalent side length can be set arbitrarily and much larger than the original wire, which can greatly reduce the computation time. Meanwhile, the method can be extended to the thin-wire structure with arbitrary cross sections. The model is verified with various measurements. Finally, a practical grounding grid of a substation with external water supply is analyzed. [ABSTRACT FROM AUTHOR]

This paper introduces application of genetic algorithm (GA) in designing air-termination system of the high-voltage (HV) open-air substation external lightning protection system (LPS). As far as the authors are informed, this is the first proposal for using GA in designing LPS of substations. The complex air-termination system, as a part of the external LPS of HV substation, is known to be cumbersome to design using traditional techniques, where optimisation is often relegated to the trial-and-error approach. In addition, traditional methods are often associated with geometric constraints and implementation difficulties. This paper proposes a novel approach which utilizes a combination of statistical LPS efficiency and GA in designing techno–economically optimal external LPS of open-air substations. The LPS optimisation problem is particularly well suited to the GA solution approach, due to the stochastic nature of lightning, expert knowledge involved in constructing the fitness function, and the fact that the optimal solution is not, strictly speaking, a unique value (it can be obtained using different combinations of the air-termination system elements). Proposed approach offers a LPS designer unique and valuable assistance in optimally arranging elements of air-termination system for obtaining maximum lightning shielding effects with minimum total investments. [ABSTRACT FROM AUTHOR]

Lightning phenomenon has resulted into several losses to both supply-side and load-side of the electricity infrastructure. Quite a handful of research has investigated strategies for its mitigation. This work is an application of the Fernandez-Diaz arrester model to the section of Eko Distribution network. The procedure involves simulation of the network in respect of the influence of the surges and surge arresters using MATLAB/SIMULINK. The study reveals that whenever lightning strikes, the resulting overvoltage causes distortion to the voltage waveform, as well as the current waveform. This indicates the presence of harmonics. Meanwhile, with the installation of the arresters, the overvoltage reduces by 86% at the nearest node of installation. However, at the other nodes within the same branch, the installed arrester attenuated the surge overvoltage by approximately 60%. This suggests that more arresters need to be installed at other nodes along the branch in order to eliminate the occurrence of overvoltage. Moreover, the study reveals that a surge arrester installed at one of the two branches of the network has negligible effect in attenuating voltage surge at the other branch of the same network. [ABSTRACT FROM AUTHOR]

A new approach to lightning transient studies including complex grounding grids is presented in this paper. The grounding system is modeled in Matlab/Simulink based on the transmission line theory. Using a bottom-up approach and considering the properties of the fundamental elements, a detailed view of measurement values will be presented and analyzed. The Matlab/Simulink grounding system models are interfaced for co-simulation with EMTP-RV trough Functional Mock-up Interface (FMI) 2.0. This modeling approach allows the use of the full component library and network design by EMTP-RV to evaluate and analyze the effects of the grounding system and transmission network simultaneously in Matlab/Simulink. The results present a simplified transmission system where a surge is injected, Conseil International des Grands Réseaux Électriques (CIGRE) 1 kA 1.2/50, in far-end of a transmission line. When reaching a substation, the surge is injected into the grounding system through a surge arrester.

In this paper, application of gapless transmission line arresters (TLAs) in substation lightning protection is analyzed. Deterministic calculations in accordance with IEC 62305 are performed. Substations with non-standard configuration equipped with Gas Insulated Switchgear (GIS), long cables, and a direct cable connecting GIS and power transformer are considered. It is concluded that 220- and 400-kV substations lightning performance can be significantly improved by using TLAs at only one or two overhead line towers in front of the substation. In some cases, TLAs provide better lightning protection of power transformer than surge arresters installed in GIS. Positive effects of TLAs application are noticed both in the case of back-flashovers and in the case of shielding failures. TLAs energy stress increases with the decrease of the system rated voltage. Maximum estimated values in the analyzed substations are below 2.5 and 0.5 kJ/kVr for TLAs installed in 220- and 400-kV systems, respectively. [ABSTRACT FROM PUBLISHER]

Lightning strikes may result in widespread power outages with long supply interruption times and severe impacts to economy and society. To prevent this from happening now and in the future, power system planning and operation practices must be revisited so that the probability of outages caused by lightning strikes can be reduced. In this context, this article presents a probabilistic framework for impact assessment of lightning strikes on the grid which investigates power system exposure to lightning strikes. This new framework incorporates information about failure rates attributed to lightning protection system design and asset condition together with the probability of lightning activity over time for a probabilistic impact assessment of lightning strikes on the grid. Notably, the probability of lightning activity is conditioned by information about weather patterns and seasons obtained through collaboration with the Met Office. Furthermore, it is demonstrated in the reduced 29-bus Great Britain transmission system model with weather data collected from 2010 to 2019 and validated against historical fault data recordings provided by the National Grid's Transmission System Performance Reports and by the National Fault Interruption Reporting Scheme. Therefore, the framework is envisaged to assist power system planners to investigate best design and maintenance practices and grid modernization interventions and power system operators to deploy smart operational measures that reduce the probability of power outages caused by lightning strikes. [Display omitted] • Probabilistic impact assessment of lightning strikes on the grid over time. • Probability of lightning activity based on UK's Met Office adopted practices. • Lightning protection failure rates given by design criteria and asset condition. • Power transmission components of concern: overhead lines and outdoor substations. • Validation through comparison with historical data of power outages in the UK. [ABSTRACT FROM AUTHOR]

The operating voltages of low-voltage control circuits in power plants and substations have decreased with the installation of digital control equipment. This increases the susceptibility of control equipment to abnormal surges, which arise mainly from lightning. To protect control equipment from lightning, it is necessary to predict lightning surges invading power plants and substations and design effective lightning protection methodologies. Compared with conventional simulation techniques based on circuit theory, full-wave numerical approaches are advantageous in handling three-dimensional structures such as transmission line towers, grounding structures, nonhorizontal wires, such as incoming power lines to power plants and substations, and lightning-induced effects. In this study, to apply the finite-difference time-domain (FDTD) method to the lightning surge analysis of an air-insulated substation, we first propose techniques for simulating the nonlinear breakdown characteristics of short-air-gap arcing horns and transmission line surge arresters installed in 77 kV transmission lines for FDTD-based surge simulations, and compare the breakdown characteristics calculated using the proposed techniques with measured results for validation. Second, as an example of the application of the proposed techniques to practical surge analysis, it is confirmed that we can reproduce the measured results of lightning surges invading a 77 kV air-insulated substation in the case of a direct lightning strike to its nearby transmission line tower by taking into account lightning-induced voltages arising from the lightning current flowing through the lightning channel and transmission line tower, which are commonly ignored in conventional circuit-theory-based simulations, multiphase back-flashover phenomena, and the effect of applied AC voltages. [ABSTRACT FROM PUBLISHER]

The electric field in and around a 2.6-m-long substation arrester, on which a 1 MV lightning impulse is imposed, has been analyzed using the finite-difference time-domain (FDTD) method. The arrester is represented as a combination of 10 mm × 10 mm × 10 mm cubic cells, each of which has a nonlinear resistivity (or conductivity) in each of the x-, y-, and z-directions, dependent on the electric field in each direction. This simple representation requires no iterative procedure, and is suitable and useful for the FDTD simulation of an overvoltage-imposed arrester. The transient electric field in and around the overvoltage-imposed arrester, and the spatial distributions of vertical and radial electric fields along the surface of the arrester are shown. The influence of a shield ring is also shown. [ABSTRACT FROM PUBLISHER]

The accuracy of lightning overvoltage evaluation of electrical equipment has been improved based on circuit analysis such as the Electro-magnetic Transients Program, but analyzing phenomena whose plane wave propagation (TEM) mode cannot be assumed remains unsolved. Since numerical analysis of electromagnetic fields such as the finitedifference time-domain (FDTD) method directly solves Maxwell?s equations, it is an appropriate means for solving this issue. In this paper, the lightning surge waveform due to the back-flashover is analyzed using the FDTD method; bearing detailed modeling of transmission towers and incoming substation lines in mind. An open end of a circuit breaker of a 500 kV air-insulated substation was selected as the subject of analysis, and ac operation voltage was considered as an analysis condition. Following FDTD analysis, a 150 kA lightning stroke to the first tower, which is the standard lightning stroke of the lightning protection design, does not cause back-flashover, but a 200 kA lightning stroke to the first tower and a 150 kA lightning stroke to the second did do so. The flashover occurred in the later timing than the result of conventional circuit analysis, and the rise of the lightning surge was also slower. The voltage waveform of the open end of the circuit breaker reached its peak after repeating reflections, and the overvoltage value became lower than the circuit analysis. According to the FDTD analysis, the required withstand voltage value after the waveform evaluation with a 200 kA lightning stroke is 1,337 kV, which is lower than the present lightning impulse withstand voltage (LIWV) 1,550 kV. The lightning stroke current 200 kA is the value adopted in the lightning protection design of the UHV system. Therefore, the existing air-insulated substation equipment is considered highly capable of withstanding overvoltage at the time of a back-flashover. [ABSTRACT FROM AUTHOR]

Higher accuracy in the lightning-surge analysis has been pursued; based on circuit analysis. However, the need to analyze phenomena where a plane wave propagation mode cannot be assumed is an outstanding issue. The finite-difference time-domain (FDTD) method is a dominant measure to solve such issue. This study evaluated surge waveforms intruding into a 500 kV air-insulated substation due to a back-flashover through FDTD simulation. The lightning surges were calculated with the inclined angle of the incoming line changed from 0 to 69 degrees and the voltage of the lightning surge intruding into the substation decreased with increasing incline angle of the incoming line. At the open end of the incoming line to the substation at the circuit breaker, the voltage was minimized and maximized when the span length was 20 m and 200 m respectively. This result differed in terms of characteristics from that obtained using the conventional circuit analysis model, whereby the voltage was minimized when the span length was 200 m. The lightning overvoltage at the circuit breaker terminal based on FDTD analysis was lower than that based on circuit analysis. Their relative ratio is 0.557 for a standard incoming line span length of 150 m, showing a 44 % reduction in FDTD analysis from the circuit analytical result. Since the current lightning impulse test voltage is evaluated based on this circuit analytical result, it was clarified that the lightning impulse test voltage level could be potentially reduced with consideration of the inclined conductors at the incoming line span, the vertical conductors of the tower and lightning path, and their mutual coupling with the transmission line. [ABSTRACT FROM AUTHOR]

A transmission tower model that can reproduce the lightning surge response is important for analyzing the lightning surge. In developing such tower model, however, studies have been conducted using a stand-alone tower or a condition where the tower and transmission lines are orthogonally crossed. This could be attributable to the difficulty in handling a complex layout in conventional experiments and theoretical studies. The present paper verifies the accuracy of the FDTD analysis, based on a comparison with the experimental results. Subsequently, it studies the influence of the layout and the inclined angle of the incoming lines to the substation on the surge response of the tower under near-real facility conditions via electromagnetic field analysis using the FDTD method. As a result, the voltage of the insulator strings peaked with a zero-degree incoming angle and it declined with increasing angle, namely by about 20% when the inclined angle was 37.5 degrees. Finally, the current waveform was analyzed in addition to the voltage characteristics and the generation mechanism of the line voltage was explained. [ABSTRACT FROM AUTHOR]

Recent lightning current observations have suggested that a front duration of 1.7 \mus is more appropriate than the conventional 1.0 \mus for the lightning protection design of ultra-high voltage (UHV) systems in Japan. This study examined overvoltages at gas-insulated subsystems (GIS) and transformers in a UHV (the rated voltage of 1100 kV) substation during backflashovers, with the front duration of lightning stroke current waveforms taken as a parameter. The dependence of overvoltages on the front duration of the lightning stroke current is significant at GIS and relatively small at the transformer. Generally speaking, the shorter the front duration is, the higher the voltage will be. The transformer capacitance, ranging from 0 to 1000 pF, equivalently increases the distance to the surge arrester, and a voltage increase was observed at the transformer terminal. However, the steepness of the intruding surge waveform is reduced and the voltage increase suppressed at 1000 pF and over. The effect of overvoltages on insulation design was also evaluated and the results thereof indicated the possibility of reducing the lighting impulse withstand voltage. [ABSTRACT FROM PUBLISHER]

Accurate predictions of lightning surge overvoltages are essential to power equipment insulation design. Recent observations of lightning strokes to uiltra-high-voltage designed transmission lines confirmed direct lightning strokes caused by shielding failure and found phenomena unexplainable by conventional shielding theories. However, there are few detailed studies of direct lightning surge overvoltages. This study assumed direct lightning stroke currents based on observational data and performs Electromagnetic Transient Program analysis of the gas-insulated switchgear (GIS) and transformer overvoltages at substations to study the basic characteristics of overvoltages due to direct lightning strokes and evaluate lightning protection design. Consequently, the maximum GIS overvoltages were found during back-flashovers, and the locations of maximum overvoltages from direct lightning strokes and back-flashovers differ. Direct lightning strokes may be more severe than back-flashovers for transformers. This paper also studied the overvoltage generation mechanism and showed the relationship of the maximum voltage to lightning stroke current and transformer capacitance. [ABSTRACT FROM AUTHOR]

This paper presents the observation results of surge waveforms in substations and the frequency components of such waveforms. In the Higashikanazu 77 kV power system, distribution transformers were damaged three times by winter lightning. In particular, almost the same parts were damaged at the No. 3 transformer in Katayamazu substation. To investigate the cause of the transformer failures, observation apparatus were installed at four substations in the Higashikanazu power system. Approximately 490 waveforms of incident surge were measured during the observed period. In 11 cases, simultaneous measurements of the incident surge waveforms at the four substations were achieved. By the analysis of the observed waveforms, the specific frequency components were found. From the investigation of theoretical and analytical approaches, it became clear that these frequency components depended on the power system configuration. By comparing the specific frequency components of the observed waveforms and the natural frequency components of the transformer, it was clearly shown that the overvoltages due to the internal resonance phenomena were the cause of failures. As a result, the internal resonance phenomena should be considered in the design of transformers, and the specific frequency components should be also estimated by the theoretical and analytical approaches. [ABSTRACT FROM AUTHOR]

The grounding systems are simply handled as lumped resistances with constant values in traditional lightning transient analysis of substation. A complete transmission line model is proposed to consider the actual transient process of power network and the grounding grid of the substation and the grounding devices of transmission towers. A loss transmission line model with time-variable parameters is proposed to calculate the transient characteristics of grounding systems under lightning current in which the soil ionization phenomena around the ground conductors are considered. The analyzed results by the proposed model have large differences with those obtained by the traditional simplified method. The transient characteristics of grounding systems have strong influence on the lightning transient process of substation. [ABSTRACT FROM AUTHOR]

EMTP has been widely used in Japan to analyze switching and lightning overvoltages to design power stations and substations from the viewpoint of insulation coordination. The Japanese standard of high voltage testing, JEC-0102-1994, and the insulation design and the coordination of an 1100-kV line of Tokyo Electric Power Company were mostly based on EMTP simulations. This paper presents a method of a lightning surge analysis using the EMTP recommended in the Japanese standard and related guidelines, and suggests further work to be done based on discussions of applicable limits and problems of the recommended models. [ABSTRACT FROM PUBLISHER]

A unique method of predicting lightning outage rates for substations, taking into account statistics-based lightning characteristics, has been developed. The proposed method features the application of a combination of two processes: a high-accuracy lightning surge analysis applying the electromagnetic transient program (EMTP) and a statistical data analysis using a general-purpose spreadsheet software. By employing an original tool applying the proposed prediction method, which is installed in a personal computer, an optimal lightning protection for substations can be designed. In this paper, several analysis models are proposed for lightning characteristics including lightning surge. The validity of the proposed method was confirmed by comparing the transmission line outage rates derived by the models with the outage data gained during actual observations. It was found that the predicted lightning outage rates for 500-kV substations were relatively low, and this finding revealed that it is possible to decrease the impulse withstand voltage level (LIWV). © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(2): 64–75, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10300 [ABSTRACT FROM AUTHOR]

In recent years, transmission line arresters have been installed to protect overhead power transmission lines from backflashovers caused by lightning. In addition, it has been expected that substation lightning surges incoming via transmission lines can be suppressed by them. However, the suppression effect by those with series gaps has not been investigated sufficiently. The author has measured lightning surges at two 77-kV substations from 1990 to 1993. As the transmission line arresters have been mounted on the towers since 1992, the lightning surges due to the sparkover of the series gap of the transmission line arresters can be observed at the substations. In this paper, the lightning surge waveforms due to such sparkover have been analyzed in detail. Next, an accurate EMTP simulation method considering the induced lightning surge voltages has been proposed. Finally, their suppression effect has been investigated by simulation corresponding to each mounting method. © 1999 Scripta Technica, Electr Eng Jpn, 126(4): 30–39, 1999 [ABSTRACT FROM AUTHOR]

In order to improve power supply reliability, it is necessary to prevent lightning faults in transmission lines and substation apparatus. However, faults are caused occasionally in lower-voltage power systems, particularly at the 77 kV level. The governing factor for insulation strength of substation apparatus is the lightning impulse voltage, and it is necessary to know the voltage level and distribution in a substation caused by lightning surges in order to investigate rational insulation coordination. For this purpose, the authors measured lightning surges at two 77 kV conventional substations from 1990 to 1993. In this paper, the characteristics of induced lightning surges and back flashover lightning surges are described. Comparisons of related surge voltages at two substations, the power line phases in grounding faults, and the equivalent capacitance of the substations are also discussed. © 1998 Scripta Technica, Electr Eng Jpn, 124(3): 40–48, 1998 [ABSTRACT FROM AUTHOR]

A new approach to lightning transient studies including complex grounding grids is presented in this paper. The grounding system is modeled in Matlab/Simulink based on the transmission line theory. Using a bottom-up approach and considering the properties of the fundamental elements, a detailed view of measurement values will be presented and analyzed. The Matlab/Simulink grounding system models are interfaced for co-simulation with EMTP-RV trough Functional Mock-up Interface (FMI) 2.0. This modeling approach allows the use of the full component library and network design by EMTP-RV to evaluate and analyze the effects of the grounding system and transmission network simultaneously in Matlab/Simulink. The results present a simplified transmission system where a surge is injected, Conseil International des Grands Réseaux Électriques (CIGRE) 1 kA 1.2/50, in far-end of a transmission line. When reaching a substation, the surge is injected into the grounding system through a surge arrester. [ABSTRACT FROM AUTHOR]