Research Of The Application And Characteristics On The Lightning-proof Parallel Gap Of The Overhead Transmission Lines

Electric power is an important energy source related to the development of the national economy,power operation in a safe and stable condition was of great significant. Lightning strike accidents have already been the major problem. At present, lightning protection measures of the overhead transmission line was to improve the lightning withstand level. But with the strengthen of the power grid and ubiquity of the reclosing devices, lightning protection measures by way of “leading” have been an important method to protect the overhead transmission line and get more and more attention.This paper investigated and surveyed parallel gaps running in Jiangsu province and studied the protective results of the parallel gap to the insulators. Results showed that the mainly parallel gaps running in Jiangsu province were used for 110 kV composite insulators and 110 kV porcelain insulator stings. Discharge traces were found on the grading ring and arcing horn of the 110 k V composite insulators and the surface of the composite insulators was undamaged.In addition, in this paper, breakdown characteristic of the lightning on the arcing horn of porcelain long rod insulators was studied. 50% lightning impulse breakdown voltage and 100% breakdown voltage was measured and under 3 conditions(without arcing horn, installed one sided arcing horn and installed double sided arcing horn). Results showed that with the increase of the distance of the parallel gaps, U50 and U100 all increased linearly. But the incensement of the voltages was very small and in the same conditions, the breakdown voltage of the double sided arcing horn was 10-70 kV higher than that of the one sided ones. the breakdown channel was recorded to study the preventive effect of the porcelain long rod insulators by the arcing horn. The breakdown channels of the one sided arcing horn all developed through the arcing horn and that of the double sided arcing horn developed through the two side arcing horns randomly. And the arc would not tilt to a specific side. The breakdown process would not do damage to the porcelain long rod insulators.In this paper, influence relations between the structure parameters of the parallel gap and the 50% flashover voltages was discussed under positive and negative polarity lightning impulse voltage. And frequency of the surface flashover was measured. The influence law of structure parameter as Z/Z0(ratio of the parallel gap and insulation distance), and Xc, Xp(distance between the end of arcing horn and center line of the insulators) were considered. Studied showed 50% lightning impulse breakdown voltage were nearly related to the parallel gap distance Z. Parameter of X has an effect on the U50 due to the change of electric field distribution.