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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).