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[Objective] In light of a growing number of oil and gas pipelines crossing or running near power lines,the issue of lightning overvoltage at these locations has garnered increasing attention within these two industries. [Methods] In this study,a calculation model was developed using COMSOL Multiphysics software to depict the generation mechanism of potential difference between pipelines and their anticorrosive coatings at locations where these pipelines cross or run near power lines.Simulation calculations were performed to analyze the impact of soil resistivity and soil layering on pipeline overvoltage amplitude.As a result,a pipeline overvoltage protection method was proposed,considering the dispersion of current over the grounding grids at nearby towers/poles. [Results] The simulation results confirmed the effectiveness of the proposed optimization solution in limiting the voltage,establishing its practical application value.Although the potential on the pipelines and the withstand voltage of their anticorrosive coatings were generally balanced,the difference between them was notably influenced by the direction of current dispersion from the grounding electrodes.Under typical soil resistivity conditions,the withstand voltage difference between the pipelines and their anticorrosive coatings remained within limits.Additionally,it was observed that individual lightning discharges alone were insufficient to cause breakdown in the three-layer polyethylene (3PE) anticorrosive coatings.However,the withstand potential difference did contribute to the enlargement of local damage points that already existed within the coatings.To mitigate the withstand potential difference,an effective approach is proposed involving adjustments to the included angle and relative distance between the pipelines and grounding electrodes at nearby towers/poles. [Conclusion] It is proposed to effectively reduce the potential difference between pipelines and their anticorrosive coatings by modifying the configuration and current dispersion dimensions of the grounding grids at nearby towers/poles.With proven technical feasibility and economical efficiency,the findings of this study serve as a valuable reference for the design,construction,safe operation,and maintenance of oil and gas pipelines.

Copyright of Journal of Guangxi Normal University - Natural Science Edition is the property of Gai Kan Bian Wei Hui 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.)

In order to ensure the safe and stable operation of high voltage direct current (HVDC) systems, this paper studies the lightning overvoltage at the neutral point of the HVDC converter transformer. The work first introduces the basic types of lightning overvoltage based on the CIGRE Benchmark 500 kV HVDC transmission system which is modeled in the electromagnetic transient program (EMTP) software. The high-frequency model of the HVDC transmission system is considered where lightning overvoltage at the converter transformer neutral point is studied at different values of the small reactance connected at neutral point grounding and different lightning strike locations. Although increasing the small reactance value can effectively suppress the lightning current, the lightning overvoltage will gradually increase. When the neutral point is grounded by 11 Ω small reactance, the lightning overvoltage is most serious, where the peak value can reach 415 kV. Also, the farther the lightning strike position from the converter transformer, the smaller the lightning overvoltage.

Dry-type air-core reactors of DC filter are important Equipments in HVDC converter stations. Four abnormal noises occurred in the pole II DC filter field of a ± 800kV converter station of china in 2020. The video monitoring shows that the dry reactor area has discharge, and the turn to turn insulation damage of dry-type reactor is found during power outage maintenance. According to the lightning location system, lightning falls at the four times of dry reactor discharge in the channel of DC transmission line. The fault recording of DC bus and DC filter shows that bipolar bus intrudes into lightning wave at the time of reactor discharge, so it is determined that reactor discharge is induced by lightning. Since arresters are paralleled on both ends, and L1 both ends withstand voltage not exceeding the design value, so the first turn-to-turn discharge shall be caused by insulation deterioration. Transmission lines of HVDC system are generally long, Equipments of converter station frequently subject to lightning intrusion. Research related to insulation aging under this working condition shall be strengthened.

Failure of the high-voltage diode rectifier caused by lightning will cause huge losses. The traditional analysis of overvoltage induced by the high-voltage diode rectifier shell under lightning stroke cannot adapt to the overvoltage process caused by lightning stroke-induced conduction invading the inside of the high-voltage diode rectifier. Therefore, this paper proposes to establish a high-frequency equivalent model of the core components of the high-voltage diode rectifier, including diodes, reactors, transformers, and overhead lines. On this basis, a lightning overvoltage model of lightning-induced conduction into the high-voltage diode rectifier is built, and the transient process of diode lightning overvoltage under the constraint of reverse recovery charge is analyzed. Then, we describe the transient distribution of overvoltage in high-voltage diode rectifiers caused by lightning stroke. The transient distribution of overvoltage induced by lightning in series diodes under different diode equivalent models is analyzed by simulation. The simulation results show that the inconsistent parameters of series diodes can easily lead to diode damage due to uneven voltage distribution when lightning strikes. Therefore, this paper puts forward a scheme to reduce lightning damage, including selecting diodes with the same parameters and adding fast-melting fuses at the transformer's secondary side and in front of the series diode bridge arm. The simulation shows that the scheme proposed in this paper can effectively prevent the high-voltage diode rectifier from being damaged by lightning strikes. [ABSTRACT FROM AUTHOR]

Lightning strikes are one of the main causes of power system trip-outs. When the overhead transmission line (TL) connected to a wind farm is struck by lightning, large currents propagate to the substation, resulting in severe problems. To enhance the performance of wind farm substations, the transient behavior during lightning must be analyzed. The main contribution of this paper is to study the lightning behavior of wind farm substations whose design is different from other conventional substations. The lightning surge overvoltages caused by back flashover and shielding-failure of the 132 kV overhead TL connected to the 33/132 kV air-insulated substation (AIS) of Miramar wind farm are calculated. This wind farm has been built in Argentina to achieve grid connection and power transmission with a total capacity of 98.7 MW. The work investigates the fast-front lightning transient overvoltages in the AIS caused by lightning flashes striking the 132 kV overhead TL. The distributed parameter model of the TL, including towers, phase-conductors, the shielding-wire, insulators, and the span, is investigated using Digsilent Power Factory software. In addition, the AIS apparatus, including surge arresters (SAs), two 60 MVA transformers, and circuit breakers, are also considered in the model. The strike is applied first at the shielding-wire, and the impact on the transient overvoltages at the TL and the substation during the back flashover phenomenon are analyzed. On the other hand, the shielding-failure is studied and the transient overvoltages at the TL and the substation are analyzed. The impact on the transient overvoltages at the TL and the substation is investigated, taking into account the SA protection operation, and its dissipated energy during lightning flashes is calculated. The study results are important for the lightning protection systems design of wind farm substations connected to overhead TLs.

Copyright of Electric Power Automation Equipment / Dianli Zidonghua Shebei is the property of Electric Power Automation Equipment Press 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.)

In order to study the influence of electrical power towers on the nearby natural gas pipelines and the protective measures when lightning strikes power towers, a power line and natural gas pipeline model was established with the professional lightning protection calculation software CDEGS, and the influence of grounding grid with a single approaching, departing and parallel epitaxial ray on the potential of pipelines was studied under different influencing conditions of current amplitude, soil resistivity and distance. Further, a pipeline overvoltage optimization scheme based on the forced commutation was proposed. The results show that, the increase of soil resistivity and current amplitude will lead to the increase of pipeline overvoltage, and increasing the distance between the power tower and the pipeline can reduce the pipeline overvoltage. With the increase of the redirection angle of the epitaxial rays, the overvoltage on the pipeline and the potential difference suffered by the coating show a decreasing trend. Generally, the forced commutation based optimization scheme proposed herein could significantly mitigate the lightning overvoltage risk of power lines to the adjacent natural gas pipelines.

In order to propose more reasonable protection measures of transformers, the electromagnetic transient of distribution transformers under the lightning strike fault should be given enough attention. In this article, a 35-kV distribution transformer under the lightning strike is taken as the research object. First, the lightning overvoltage model of the transformer is established utilizing the double exponential model. The electromagnetic transient change of the transformer under the rated voltage superposed the lightning overvoltage is analyzed. Second, the magnetic flux distortion of the transformer core and the current distribution law of the transformer windings during the lightning invasion are calculated and summarized, respectively. Finally, on the basis of revealing the whole process that the lightning wave invades the transformer windings, a new type design scheme of transformer lightning protection is proposed. The results show that the additional windings of the lightning protection scheme can greatly reduce the positive and negative overvoltage of lightning wave acting on the transformer. The feasibility of the proposed protective measures is verified, which can provide some scientific references for improving and perfecting the lightning protection measures of the distribution network. [ABSTRACT FROM AUTHOR]

Horizontal grounding conductor is often used to obtain low grounding resistance. Simulation results of voltages and currents in a circuit including a grounding system are sometimes different from measured results because the grounding resistance depends on temperature and water content. Lightning surge characteristics of a grounding conductor are important for lightning protection design. Simple formulas for the surge characteristics of the grounding conductor are useful for engineers to estimate the influence of parameters of grounding system on lightning overvoltages. This article describes measurement results of the surge characteristics of grounding conductors for various conductor lengths and terminal conditions. This article proposes simple formulas for surge impedance and propagation velocity of horizontal grounding conductor based on the measured results. A simple equivalent circuit of grounding conductor is described. The constants of the equivalent circuit are obtained using the proposed formulas. Simulation results of voltage on a grounding grid using the proposed formulas and the equivalent circuit of grounding conductor are compared with experimental results. [ABSTRACT FROM AUTHOR]

• Analysis of the lines shielding failure and back flashover performance. • Investigating the impact of each flashover parameter by multivariate analysis. • Simulated fault waveforms exhibit similar pattern with recorded field waveforms. • The average peak voltage difference between the simulated and actual data is 6 %. • Obtained waveforms are useful for designing lightning fault classification system. Lightning overvoltage causes outages of transmission lines (TLs) in tropical countries. Identifying and analyzing the key factors responsible for tripping the lines can improve the performance of the lines. In this work, the flashover patterns due to direct lightning strikes on 275 kV double circuit TLs and towers in Malaysia was evaluated with Electromagnetic Transient Program (EMTP-RV). Three parameters that include lightning current magnitude, power frequency angle and tower footing resistance were analyzed on the line performance during direct lightning strikes. The simulated results found that two key parameters, lightning current at 270 kA and footing resistance at 50 Ω, reveal the highest impact on the insulator flashover. This finding was also verified from multivariate analysis results which is rarely found in the previous works in this field. As a key contribution in this work and in validation to the model, the simulated fault waveform patterns and voltage magnitudes were compared with the actual site data obtained from six different locations in Peninsular Malaysia. The analyzed results show a similar waveform pattern with an overall average voltage magnitude difference of 6.0 % before and after fault. The model is useful to electric utilities for analyzing transient performance of TLs. [Display omitted] [ABSTRACT FROM AUTHOR]

Purpose. The complex approach to calculating thunderstorm overvoltage on substation equipment is considered when lightning strikes in a lightning rod. Methodology. The conditions of safe passage of lightning current through a lightning arrester are formulated. Results. It is shown that the calculation of the permissible length of air insulating gaps in the substation is based on the breakdown of the air tension, which is assumed to be 500 kV/m. This leads to an error in calculating the length of the air gap and, as a consequence, the probability of its breakdown, the value of which is used to calculate the indicator of the lightning resistance of the substation. A technique is proposed for calculating the permissible voltage on the transformer case when a lightning strike strikes the lightning receptacle of the transformer portal. On the basis of the nonlinear pulsed electric strength of the ground, the specified minimum permissible ground distance between the grounding rod of the lightning rod and the nearest point of the protected device is obtained. Originality. Refined calculation of the length of the minimum breakdown gap in the air and in the ground. Practical value. The proposed approach makes it possible to calculate thunderstorm overvoltage on substation equipment.

Growing urbanization coupled with increased power demands have led to increasing use of mixed power transmission lines with sections of overhead lines (OHL) and underground cables. Due to differences in surge impedance of cables and OHL, voltage surges experience reflections and refractions at their boundaries which make the transient behavior of mixed high voltage direct current (HVDC) line quite peculiar. Lightning strikes on overhead sections of lines induce voltage surges that travel along OHL and enter the cable section. Lightning overvoltage can cause OHL insulators to flashover and stress cable insulation or cause its permanent breakdown. In this paper, we simulated a fast front model of a mixed HVDC transmission line using an electromagnetic transient simulation program (PSCAD) to analyze its transient behavior under a lightning strike. The leader progression model has been used to predict the dielectric performance of OHL insulators. It has been shown that transition towers adjacent to the cable section are much less vulnerable to flashover than subsequent towers. The length of a riser section (connecting OHL and cable) and tower footing impedance have shown to significantly influence the flashover performance of OHL insulators. In addition, the length of cable segments and sheath grounding impedance has been found to influence cable overvoltage. This paper can be used to evaluate the insulation coordination and overvoltage protection requirements for a mixed HVDC transmission line.

Corona is the partial discharge that occurs around the wires and edges in inhomogeneous electric field. Minimum intensity of the electric field for the impact ionization of the gas is around 2.6 MV/m in dry air. In power systems, the corona is the unwanted effect caused by overvoltages. In this study the propagation of the overvoltage wave due to negative lightning along the transmission line is numerically simulated. The effect of the corona is modelled by the drift-diffusion-reaction equations for the electrons, the positive and the negative ions. [ABSTRACT FROM AUTHOR]

Due to the high UHV AC/DC transmission line tower, the working voltage amplitude on the wire is large, causing lightning accidents. The paper first analyses the impact of lightning strike point on lightning overvoltage of 1000 kV UHV transformer substation and determines the research object of lightning intruding wave overvoltage. Second, the influence of the impact grounding resistance of transformer side lightning arrester and transmission line tower on invaded wave is analysed. Finally, the commutation failure of HVDC system was analysed, and the simulation tests were carried out by CIGER standard model in PSCAD and Simulink, valve voltage and valve current waveform can be used as a new basis for judgment. The conclusion shows that the analysis of UHV AC/DC hybrid system commutation failure should start from the DC system to study, and commutation failure directly related to the failure, operating conditions, and other factors.

In this paper, the effectiveness of lightning overvoltage protection of cables in high voltage overhead cable lines has been analyzed. Because of the high overvoltage level, the cables are protected by surge arresters and by metallic sheath earthing. However, in practice, quite a lot of cases of electricity-evoked damage to the cable outer sheaths are observed, proving that the effectiveness of the protection used is insufficient. As a result, the cables are exposed to environmental factors, especially moisture penetration, which contributes to cable degradation. To explain the causes of this situation, simulation studies were carried out to determine the relevant factors affecting the level of expected overvoltages. The circuit-field model of the overhead cable line in EMTP-ATP, COMSOL and MATLAB software was used for determining overvoltages on the main cable insulation and the outer protective sheath. The studies reveal that the efficiency of the cable insulation overvoltage protection is ensured regardless of the lightning strike location and the crest value of its current. However, the obtained results confirm that no matter the applied protection, the cable outer sheaths may be exposed to overvoltages with higher values than those of the main insulation. Although the analysis was performed for 110 kV lines, the conclusions are general and are also applicable to power lines with higher rated voltages.

Lightning-induced overvoltage in substations is one of the main causes of insulation damage in transformers. As the complexity of power grids is continuing to increase, the existing lightning overvoltage statistical waveform may no longer meet the requirements of modern power systems. It is therefore necessary to obtain the statistical characteristics of lightning-induced overvoltage on transformers. However, the existing devices in current power systems cannot meet the requirements for monitoring of the lightning-induced overvoltages because of their limited bandwidths and sampling rates. This paper proposes a method for monitoring of lightning-induced overvoltages on substation transformers based on the principle of ZnO lightning arrester block voltage division. Consistency testing was performed on the voltage division ratio of a ZnO lightning arrester block in both the linear and nonlinear regions. The experimental results confirmed the feasibility of the proposed method and field applications using this sensor showed that long-term research will be helpful in obtaining the characteristics of lightning-induced overvoltage. [ABSTRACT FROM AUTHOR]

In order to study the problem of damage that caused by lightning overvoltage to the transistor, we designed the experiments of combined wave impact on the transistor under different conditions by analyzing the theory of the secondary breakdown of the transistor caused by the lightning electromagnetic pulse. These cases are carried out under the condition of no protection, transient protection diode (TVS) parallel protection, and TVS tube parallel protection in the actual base amplifier circuit. It is concluded that transistor can cause it to further deteriorate under the condition of lightning overvoltage impact, and the situation of the damage can be divided into two categories, transient suppression diode in parallel with a transistor that is struck by a lightning voltage can effectively protect the transistor, which can obviously improve the resistance of the transistor. In practical amplifying circuit, applied voltage reduces the tolerance level of transistors, however, the tolerance level of transistors with transient suppression diodes in parallel is still better than the tolerance level without protection, which confirmed the conjecture that transient suppression diodes can be applied to actual circuits to protect transistors in parallel. In this paper, the theoretical analysis and experimental research on the damage of the lightning voltage on the transistor, the tolerance level of the transistor to the lightning voltage and the protection effect of the TVS tube on the transistor are carried out, which has certain reference value in the actual lightning protection of the transistor. [ABSTRACT FROM AUTHOR]

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.)

Wind turbine generators in a windfarm are connected by underground cables. Lightning sometimes strikes a nacelle or a blade. Lightning overvoltages due to a direct lightning strike to the system cause damages in the underground cable. Many parameters should be investigated to establish a rational lightning protection design for wind power generation system. Numerical simulation is a useful method to discuss the influence of the parameters on the lightning overvoltages. This paper uses an Electro-Magnetic Transients Program for the lightning surge analysis. This paper discusses the influence of grounding method of metallic sheath of the cable and grounding resistance on the lightning overvoltages for the direct lightning strike to the generation system. [ABSTRACT FROM AUTHOR]

Due to the high UHV AC/DC transmission line tower, the working voltage amplitude on the wire is large, causing lightning accidents. The paper first analyses the impact of lightning strike point on lightning overvoltage of 1000 kV UHV transformer substation and determines the research object of lightning intruding wave overvoltage. Second, the influence of the impact grounding resistance of transformer side lightning arrester and transmission line tower on invaded wave is analysed. Finally, the commutation failure of HVDC system was analysed, and the simulation tests were carried out by CIGER standard model in PSCAD and Simulink, valve voltage and valve current waveform can be used as a new basis for judgment. The conclusion shows that the analysis of UHV AC/DC hybrid system commutation failure should start from the DC system to study, and commutation failure directly related to the failure, operating conditions, and other factors. [ABSTRACT FROM AUTHOR]

Nowadays, the analysis of the lightning performance of high-voltage (HV) underground sections has become increasingly important, thanks to their increasing usage with overhead transmission lines. In this way, the objective of this paper is to investigate the sensitivity of the overvoltages, at the terminal of underground cables (UCs), due to the incidence of negative lightning flashes at the shield wire or the tower top. It is done by means of different representations of the grounding behavior, different points of lightning incidence, different values of soil resistivity, and considering or not the variation of the soil electrical parameters with frequency. It is observed that a reliable investigation on lightning overvoltages is important and it must consider a suitable representation of the grounding behavior. An improper modeling can lead to nonrepresentative results. In this way, it is highlighted how the frequency dependence of the soil parameters influences the results in many different situations. For long distances from the UCs and low soil resistivity regions, all the grounding models produce similar results. On the other hand, for regions with high soil resistivities, the use of a proper model for the tower grounding is important, since the discrepancies between the results produced considering or not the dependence of the soil parameters with frequency become substantial. The inclusion of the grounding behavior with frequency allows to obtain reliable simulations of the transient behavior of the insulated cables, which constitute the underground section under study. [ABSTRACT FROM AUTHOR]

Protection of transformers, as one of the most expensive equipment in the power system, against lightning overvoltage impulses is a vital task. This paper, for the first time so far, investigates the effects of a filtered spark gap on the protection level of transformers against lightning overvoltage impulses. The filter is an inductor that is placed in series with the transformer and before the spark gap aiming to reduce the voltage at the connection point of the spark gap, and hence, enhancing the protection level of the transformer under lightning overvoltages. The experimental laboratory tests are accomplished on a 400 kVA, 22/0.4 kV, Delta-Star ( Δ − Y ) connection type transformer under 110 kV, and 125 kV overvoltage impulses, whereas the size of the spark gap is set to 80 mm and two inductors of 35 μ H and 119 μ H are considered. In order to perform a more in-depth analysis, a model that works reasonably close to the empirical case is developed in the EMTP-RV software. An optimization algorithm is used to determine the sensitive parameters of the double-exponential function, which is used to reproduce the applied laboratory lightning impulse voltages in the EMTP-RV environment. Moreover, the transformer is modeled according to the Cigre Guidelines (Working Group 02 of Study Committee 33). The behavior of the spark gap is simulated as close as the practical situation using the disruptive effect method. The preciseness of the simulated filtered spark gap model is verified by comparing the results of the simulated model in the EMTP-RV with the results of experimental tests. After verifying the model, different sizes of inductors are studied in the EMTP-RV environment to investigate whether larger or smaller inductors provide better protection for the transformer under lightning conditions. A comparison is performed among the conventional spark gap, surge arrester, and the filtered spark gap to provide a better analysis of the potential of the proposed device. The results indicate that proper sizing of the inductor, within an effective range, slightly enhances the protection level of the transformer.

Transient overvoltages appearing at line terminal of power transformer HV windings can cause failure of winding insulation. The failure can be from winding to ground or between turns or sections of winding. In most of the cases, failure from winding to ground can be detected by changes in the wave shape of surge voltage appearing at line terminal. However, detection of insulation failure between turns may be difficult due to intricacies involved in identifications of faults. In this paper, simulation investigations carried out on a power transformer model winding for identifying faults between turns of winding has been reported. The power transformer HV winding has been represented by 8 sections, 16 sections and 24 sections. Neutral current waveform has been analyzed for same model winding represented by different number of sections. The values of α (‘α’ value is the square root of total ground capacitance to total series capacitance of winding) considered for windings are 5, 10 and 20. Standard lightning impulse voltage (1.2/50 μs wave shape) have been considered for analysis. Computer simulations have been carried out using software PSPICE version 10.0. Neutral current and frequency response analysis methods have been used for identification of faults within sections of transformer model winding.

In order to solve the frequently occurring lightning flashover problems on ±500 kV dc transmission lines in China, the authors have conducted the research on the dc line arrester since 2011. In this paper, the structure and installation, technical parameters, and protection performances, as well as their deterministic processes of the arrester are presented and analyzed in detail. In 2013, the authors successfully developed the arrester products, and the type tests show that they have excellent performance parameters and can act effectively against the lightning impulse and cutoff the dc follow current. By now more than 500 dc line arresters have been installed and used on seven ±500 kV dc transmission lines in eight provinces of China. About four years of operating experience shows that the arresters work safely and reliably over a long period of time, and have been effectively reducing the lightning flashover rate of the ±500 kV dc lines. [ABSTRACT FROM PUBLISHER]

• Analysis of NGLA, EGLA, and MCIA performance on mitigating double circuit tripping. • Installing four arresters per tower is the most optimal and universal solution. • All arresters are operating below manufacturers' maximum discharge energy level. • MCIA discharges 54% and 44% less energy than NGLA and EGLA respectively. • The most suitable arrester was selected based on the proposed protocol. Direct lightning strikes on overhead lines and towers causes power system outages. Optimal surge arrester placement is a practical and economical protection technique. From research trends, three types of transmission line arresters are in practice: Non-Gapped Line Arrester (NGLA), Externally Gapped Line Arrester (EGLA) and Multi Chamber Insulator Arrester (MCIA). This study proposed a simplified guide for selecting the most suitable line arrester considering the placement configurations, double circuit outage prevention and energy capabilities. Electromagnetic Transient Program was implemented to analyze back flashover performance of a typical 275 kV double circuit transmission line in Malaysia. Critical flashover parameters considered are lightning current magnitude, tower footing resistance, and power frequency angle. Analyzed results from the three arresters found that installing four arresters, two per circuit, at the lower and upper phases respectively, is the most optimal and universal double outage mitigation technique. Energy comparison reveals that MCIA discharges 54% and 44% less energy than NGLA and EGLA respectively. Also, from 132 kV system results, MCIA discharges 74% and 22% lesser energy respectively. From further validation of the simulation model, NGLA discharged 23.8% more energy than EGLA from experimental results. The proposed guide is applicable to double circuit lines below 275 kV. [ABSTRACT FROM AUTHOR]

This paper describes observation of lightning overvoltages in a 500 kV switching station at Kansai Electric Power Co., Japan. Three types of lightning overvoltages, such as back flashover, direct lightning hit to a phase conductor, and lightning-induced voltage have been observed. The lightning overvoltages due to a back flashover were lower than operation voltage of a surge arrester. The observation suggests that induced voltage caused by electromagnetic fields radiated from a lightning channel affects lightning overvoltages in a station. [ABSTRACT FROM AUTHOR]

Measurement of lightning and switching transient overvoltage in power system is significant to the research that guides the protection of power system. A new type of sensor for non-contact measurement of lightning and switching transient overvoltage in power system is designed in this study. This sensor is composed of two parts, namely, voltage induction and optoelectronic conversion units. Given the existing stray coupling capacitor C 1 between the transmission line or bus bar and a metal plate placed under it, a voltage induction unit is designed by utilizing the C 1 and a capacitor with fixed value C 2 connected in series, then the high-voltage non-contact induction on a transmission line or bus bar is achieved. The optoelectronic conversion unit is designed based on the Pockels effect of the LiNbO 3 crystal. The voltage signal induced by the voltage induction unit can be converted to an optical signal by the optoelectronic conversion unit for long-distance transmission through optical fibers without power supply at the monitoring site. Laboratory and field tests revealed that the new developed sensor possesses good linear region, high precision, and wide frequency band of the response to lightning and switching transient overvoltage in power system. The sensor can also be applied to the non-contact measurement of lightning and switching transient overvoltage in power system with different voltage levels by conveniently adjusting the distance between the sensor and the line. [ABSTRACT FROM AUTHOR]

Metal–oxide surge arresters (MOSAs) are essential equipments for power system protection and devices from lightning and switching transient overvoltages. Therefore, their operating condition and diagnosis are very important. In this study, a multi‐layer support vector machine (SVM) classifier has been used for MOSA conditions monitoring based on experimental tests. Three features are extracted based on the test results for determining surge arresters operating conditions including clean virgin, ultraviolet (UV) aged clean surface, surface contaminations after and before UV housing ageing, and degraded varistors along active column. Then, the multi‐layer SVM classifier is trained with the training samples, which are extracted by the above data processing. Finally, the five fault types of surge arresters are identified by this classifier. The test results show that the classifier has an excellent performance on training speed and reliability which confirm the high applicability of introduced features for correct diagnostic of surge arresters conditions. [ABSTRACT FROM AUTHOR]