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Parallel gaps, as a new mode of "channel" type lightning protection, can do it with the sub insulator arc distance to effectively protect the insulator, but the corresponding line tripping rate will be affected because of this; Development method based on the leader in this paper the calculation method of the lightning path, the typical used tower of guangzhou trip rate change after the application of parallel gap situation has carried on the analysis, got a short distance and adopt reasonable reinforced insulation, the trip rates did not rise significantly.

The fault of transmission line is mostly caused by lightning, and a ground lightning stroke process is often accompanied by multiple strokes. The duration of ground lightning stroke are also different. In this paper, a method for evaluating the reclosing time of reclosure based on lightning parameters is proposed. In addition, this paper also gives an expression for the cumulative rate of the duration of ground lightning stroke, and an expression for probability distribution of the amplitude of lightning current in Guangdong area. We also proposed a method for calculating the probability of tripping of reclosure. By this calculating method, the average probability of tripping of reclosure is less than 1/10000 during a ground lightning stroke process, when the reclosing time t0 is greater than 1.012s.

In this paper, the actual trip of typical transmission line is analyzed. It includes the trip frequency of transmission lines and the tripping frequency caused by lightning, seasonal distribution characteristics of transmission line trip, and the success rate of reclosing on the transmission line. In this paper, the probability of the occurrence of the trip again is evaluated based on the duration of ground lightning stroke. With the increase of the time of reclosure, the probability of the occurrence of the trip will decrease. By this calculating method, the average probability of tripping of reclosure decreased significantly during a ground lightning stroke process, when the reclosing time t0 is 1s.

As a new kind of lightning protection, parallel gaps have simple structure, easy installation, good economy, and many other advantages. The traditional parallel gap due to the large short distance, can lead to lightning trip-out rate increases. Based on arc movement characteristics this paper presents a design of new type of parallel gaps and the analysis of the surface field strength, and the verification test, design a new kind of parallel gap are obtained.

Lightning is one of the most important reason of outage of distribution line. And nearly 90% of the accidents of lightning failure is result of lightning induced overvoltage. In order to protect the distribution line from lightning, it is required to have a comprehensive understanding of characteristic of lightning induced overvoltage. Due to the advantage of reduced scale experiment, which are controllable and practical, the characteristic of lightning induced overvoltage is got from it. Comparing the results of experiment with the results of calculation, it is found that changes of overvoltage with height and distance match well with the calculated results, which show that the reduced scale experiment is effective and proper.