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This paper presents the study on the potential distribution of the ac 1000-kV ultra-high voltage metal-oxide arrester (MOA). Based on the idea of field-circuit combination, the 3-D finite-element method (FEM) and circuit-analytic method are applied to analyze and improve the potential distribution of the 1000-kV MOA. The 3-D FEM is used to obtain the 1000-kV MOA's potential distribution and stray capacitances to build the equivalent circuit of the MOA. With the equivalent circuit, the method to improve the potential distribution of the MOA by adding parallel capacitors is analyzed. A scheme to obtain the recommended values of parallel capacitors is achieved to improve the potential distribution coefficient within [+ or -] 5%. In addition, the influences of the grading ring and mounting height of the MOA on the potential distribution are also discussed. The potential distribution of the developed 1000-kV surge arrester was tested by the photoelectricity measurement method, which is close to the analysis results. Index Terms--Circuit analysis, finite-element method (FEM), metal-oxide arrester, parallel capacitor, photoelectricity measurement method, potential distribution, ultra-high voltage (UHV).

Three-phase short-circuit arcs often cause the breakage of covered conductors on distribution lines, and their movement processes have become an important problem in power-distribution systems. This paper presents the studies on the movement simulation of the three-phase short-circuit arcs. Based on the latest electric arc model and the coupling of magnetic field and motion, this paper develops the procedure to simulate the movement processes of the arcs. Simulation results show that the arcs have different movement directions and behaviors, which are in agreement with the experimental phenomena. This paper is very helpful to design an effective device that prevents the arcs from causing the breakage of the conductor and the damage of the insulator. Index Terms--Distribution line, magnetic field, movement simulation, three-phase short-circuit arcs.

Covered conductors have been widely used on overhead distribution lines, and are very easily broken by short-circuit arcs caused by direct lightning strokes or lightning induced overvoltages. The analysis and comparison of all measures and devices to prevent breakage of covered conductors applied in different countries are presented. All of these methods are classified into three categories according to their operation principles, and according to their functions, these methods are summarized into the arc-blocked method and the arc-guided method. Index Terms--Covered conductor, distribution line, insulation layer, lightning stroke, power frequency arc, protection measure, shield wire, surge arrester.

For the problem of lightning breakage of covered conductors on overhead distribution lines, two kinds of 10-kV surge arresters, namely a metal-oxide arrester with a ring-shaped series gap and stab electrode metal-oxide arrester with series gap were developed in this paper. Their structure, installing mode, and experiments were presented. Large amounts of lightning impulse flashover tests validate that these arresters have good effects. Based on these developed arresters, the protection measure for a 10-kV feeding line in substations was proposed. Now these arresters have been applied in China and have the potential for wide applications prospect. Index Terms--Breakage, covered conductor, distribution line, lightning stroke, power frequency arc, surge arrester with series gap.

The electric fields under high-voltage direct current (HVdc) transmission fines and the ions produced by corona affect each other greatly. This paper presents an iterative method to calculate ion flow fields under HVdc bipolar transmission lines in the presence of wind. Both the electric fields and the ion densities are calculated by integral equation method. The method is fast and stable. The results are in good agreement with the experimental data. The ion flow fields under a [+ or -] 800-kV bipolar direct current (dc) transmission line are analyzed. Index Terms--Electric fields, high-voltage direct current (HVdc) transmission lines, integral equations, ions.

Based on the field-circuit equivalence concept, the equivalent circuit to analyze the voltage distribution of a 500-kV dc transmission-line voltage divider under impulse voltages has been developed. The hybrid finite-element analytical approach is applied to extract the capacitance and inductance parameters of the equivalent circuit, and the Milne method is used to solve this complicated circuit. The voltage distribution along the resistor coils of the divider under impulse voltages is calculated and its nonuniformity is discussed. The analysis results are in good agreement with the measurement results. The selection of capacitors parallel with the resistor turns to improve the voltage distribution along the resistor coils is studied, and the optimal selection of these capacitors is suggested. Index Terms--DC transmission line, impulse voltage, voltage distribution, voltage divider.

It is essential to extract the stray parameters accurately and efficiently in analyzing impulse responses of a power apparatus. In this paper the stray capacitances and stray inductances of a 500-kV dc transmission-line voltage divider are extracted by the hybrid finite element-analytical approach, and the corresponding equivalent circuit for analyzing the impulse voltage response of the voltage divider is established. According to the discussion of the results of the extracted stray parameters of the voltage divider, reasonable simplification of the equivalent circuit of the voltage divider is made. In addition, the influence of the insulating housing and the electrical insulation oil on the stray capacitances of the voltage divider is discussed. Index Terms--DC transmission line, field-circuit equivalence, hybrid finite-element-analytical approach, impulse voltage, parameter extraction, voltage divider.

This paper presents the study of a long electric are in free air due to lightning stroke on the parallel gap lightning protection device (PGLPD) on high-voltage overhead transmission lines. Based on the latest electric arc model, the analysis method of the magnetic field generated by the current flowing through the PGLPD, electric arc, transmission lines, steel tower, and ground wires is developed, and the movement process of the long arc along the surface of the insulator strings is simulated. The simulation results are in agreement with the experimental results. The study is very helpful for the optimal design and suitable assemblage of the PGLPD. Index Terms--Long electric arc, movement simulation, parallel gap lightning protection device (PGLPD).

Lightning is the main cause of transmission line failure, and it is important to improve the lightning protection level of the transmission line for the stability of the power system. Traditional solutions for the shielding failure of transmission lines is to use the electrical geometric model method. However, with the improvement of the voltage level, the physical size increases, and the calculation of lightning protection for ultrahigh-voltage dc lines has a greater difference with operating experience. Based on the Ningxia-Shandong dc transmission lines in China, this study utilised the lead development model to describe the flashover of insulators and the breakdown of the gaps. A comprehensive calculation method of shielding failure trip-out rate considering terrain, earth resistance and weather was proposed. The accuracy was much higher when compared with the traditional calculation and the result can be a reference for other similar calculation for dc lines. [ABSTRACT FROM AUTHOR]

In order to solve the operation problems of traditional lightning protection equipment (for example, line arrester and parallel gap) for 220 kV AC transmission line, a novel lightning protection equipment – lightning flashover limited equipment for 220 kV AC transmission line – has been developed successfully, which owns the advantages of line arrester and parallel gap. Technical parameters, and electrical and mechanical performances are researched through theoretical calculation and experimental verification, and an installation structure of new split type is designed. The results show that the lightning flashover limited equipment has good electrical and mechanical performance and meets insulation, tensile, and bending requirements. By now, more than 200 sets of lightning flashover limited equipment for 220 kV AC transmission line have been applied on lines in four provinces of China. About 2 years of operating experience show that all the sets of lightning flashover limited equipment work safely and reliably. [ABSTRACT FROM AUTHOR]

In order to improve the lightning withstand level of ±660 kV DC transmission line in China, the authors had begun to develop the ±660 kV DC line arrester since 2014, which was developed successfully in 2016. The structure, technical parameters, protection performance, and installation of line arrester are analysed in detail. The arrester adopts the structure of polymer housing with an external series air gap and a four-section body. The technical parameters and protection performance are designed and calculated according to the relevant standards. The results show that the arrester has good electrical and mechanical performances, and it meets the requirement of insulation coordination. Pillar insulator supporting installation is used in the arrester application. Up to now, the ±660 kV DC line arrester has been used in the ±660 kV DC transmission line in China, which works safely and reliably over a long time. The successful operation can accumulate operating experience and provide a basis for the large-scale application of the line arrester on the ±660 kV DC transmission line in the future. [ABSTRACT FROM AUTHOR]

A single-station-based lighting mapping system comprising a microphone array, which detects electromagnetic (EM) and thunder signals, has recently been developed and deployed for lightning observations. Using one microphone array consisting of 19 electret microphones installed on a 3-D steel frame, this system receives and processes the EM and thunder signals to determine the location of lightning thunder sources. We implement a new broadband direction-of-arrival estimation technique, namely, the maximum power beamforming algorithm and derive the 3-D location results based on the time difference between the acoustic signal and the EM signal. In this paper, four cloud-to-ground flashes with different branch channels recorded by the system are analyzed and presented in which the located thunder sources of two lightning flashes are compared with the photograph of the high-speed camera. The details of the system implementation along with the successful reconstruction of the lightning channel in 2-D and 3-D space are discussed. The results indicate that the location system could effectively map the lightning thunder sources, and the result is highly consistent with the high-speed video camera images. Moreover, the acoustic mapping system is capable of locating the main channel produced by the return stroke process; it also depicts the branching channels. It is shown that the system is capable of distinguish different branches of the same lightning; it also obtains different lightning channels occurring almost simultaneously. [ABSTRACT FROM AUTHOR]

This article proposes the deconvolution method to evaluate the lightning channel-base current from the lightning magnetic field. We have verified the method using the magnetic field with/;without noises. The deconvolution results are both in good agreement with the simulated current. Also, we have discussed the deconvolution results when the condition number of the deconvolution matrix, $U_{{0}}$ , is different, and found that the deconvolution results will oscillate if the condition number of $U_{{0}}$ is very large. Note that the deconvolution method presented in this paper also works when using other engineering current models, such as transmission line (TL) model, and the modified TL model with exponential current decaying with height model, and so on. The deconvolution method is an efficient method to evaluate the lightning channel-base current from the electromagnetic field. This approach is also useful in research related to lightning characteristics and lightning protection. [ABSTRACT FROM PUBLISHER]

A systematic evaluation of the performance of the World Wide Lightning Location Network (WWLLN) over the Tibetan Plateau is conducted using data from the Cloud-to-Ground Lightning Location System (CGLLS) developed by the State Grid Corporation of China for 2013-15 and lightning data from the satellite-based Tropical Rainfall Measuring Mission (TRMM) Lightning Imaging Sensor (LIS) for 2014-15. The average spatial location separation magnitudes in the midsouthern Tibetan Plateau (MSTP) region between matched WWLLN and CGLLS strokes and over the whole Tibetan Plateau between matched WWLLN and LIS flashes were 9.97 and 10.93 km, respectively. The detection efficiency (DE) of the WWLLN rose markedly with increasing stroke peak current, and the mean stroke peak currents of positive and negative cloud-to-ground (CG) lightning detected by the WWLLN in the MSTP region were 62.43 and -56.74 kA, respectively. The duration, area, and radiance of the LIS flashes that were also detected by the WWLLN were 1.27, 2.65, and 4.38 times those not detected by the WWLLN. The DE of the WWLLN in the MSTP region was 9.37% for CG lightning and 2.58% for total lightning. Over the Tibetan Plateau, the DE of the WWLLN for total lightning was 2.03%. In the MSTP region, the CG flash data made up 71.98% of all WWLLN flash data. Based on the abovementioned results, the ratio of intracloud (IC) lightning to CG lightning in the MSTP region was estimated to be 4.05. [ABSTRACT FROM AUTHOR]

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]

We studied the effects of indium doping on the microstructure and electrical properties of ZnO varistors co-doped with Al 2 O 3 and Ga 2 O 3 . Scanning electron microscopy, current–voltage testing, capacitance–voltage testing, and X-ray diffraction were performed. The results showed that the leakage current of sintered varistors decreased as the indium dopant concentration was increased. The average grain size decreased slightly with increasing indium content, which improved the voltage gradient. A certain amount of the doped In 3+ dissolved into the grains causing the grain resistance to decrease, which resulted in a low level residual voltage. The sintered samples with 0.024 mol% indium, 0.2 mol% aluminum, and 0.42 mol% gallium showed excellent overall performance, exhibiting a nonlinear coefficient of 58.8, a leakage current of 1.82 µA/cm 2 , a 1-mA residual voltage of 433.9 V/mm, and a residual voltage ratio of 1.53. The obtained co-doped ZnO varistors will provide better protection and stability in applications as metal oxide arresters for power systems. [ABSTRACT FROM AUTHOR]

The overhead catenary system of high-speed railway, usually supported by viaducts, attracts more direct strikes than the conventional railway. However, there are ten thousands of slender steel rods in the reinforced concrete structure of viaducts. Therefore, it takes a lot of time to calculate the model of a long series of viaducts by the conventional electromagnetic field modeling method. An electromagnetic transient model for high-speed railway viaducts struck by lightning based on the decoupling method is proposed in this paper, in which the railway viaducts are divided into the box girder unit and viaduct pier unit. The viaducts model based on decoupling method (VMDM) is established by a series of box units supported by viaduct pier units at equal intervals. The equivalent circuit model of each unit was obtained by employing the vector fitting method based on the frequency-domain response. Experimental results of a newly built railway viaduct pier under lightning impulse current were presented to validate the equivalent circuit model of viaduct pier unit, which show high consistency with simulation results. In particular, the typical VMDM model of Beijing-Tianjin intercity railway viaducts was established with the proposed method. The result obtained from the VMDM model are compared with the simplified model. [ABSTRACT FROM PUBLISHER]

In order to investigate the different features of the positive leader propagation in the rod–plane and inverted rod–plane gaps, the discharge experiments in a 3-m rod–plane gap and a 3-m inverted rod–plane gap were carried out under switching impulse voltage. The positive leader propagation process was recorded by using a high-speed CCD camera. Some aspects to describe the positive leader propagation characteristics of the rod–plane and inverted rod–plane gaps are obtained and compared in this paper, including the critical corona radius, the average continuous leader inception voltage, the axial leader velocity, and the final jump length. The possible reason resulting in those differences is also discussed here. [ABSTRACT FROM PUBLISHER]

Experiments on the motion of long alternating current arcs in atmospheric air show that the anode and cathode arc roots have different motion characteristics because of different formation mechanisms. During a half cycle of the arc current, the anode arc root moves towards the direction of magnetic force and occasionally has a jumping motion, while the cathode arc root moves sufficiently slow to consider it stationary and hardly has any jump. The arc column has a complex shape and moves under the drive of the magnetic force and is also quickened by the lower arc root. [ABSTRACT FROM AUTHOR]