Research On The Lightning Back-Flashover Performance Of Transmission Lines

The voltage level and transmission capacity of transmission lines are increasing, and once a fault occurs, it will cause a wide range of trip, which will cause serious economic losses. In addition, the increasing of the size of the transmission line corridor and triggered lightning leads power grid more vulnerable to lightning. At present, the operation of EHV / UHV power grid has happened a large number of lightning accidents, the safety operation of the transmission line has got a serious threat. There are two main reasons for the high rate of lightning trip-out rates of transmission line: one is that the design of the calculation method of lightning over-voltage is not reasonable, and it results in the defects on the lightning protection designing of transmission lines; and the second is that is can’t focused on the influencing factors of lightning protection level of the corresponding improvement measures to reduce the rate of lightning trip. So only establish the calculation model of counter over-voltage accurately and reasonably and take measures to improve the influence factors of lightning withstand level pertinently can better assess the lightning performance of transmission lines, reduce trips caused by thunder struck, improve the reliability of power supply, ensure the safety of power grid, and provide protection for our country to build a strong smart grid.This paper based on the electromagnetic transient simulation software PSCAD / EMTDC and built the simulation model of calculating the lightning striking voltage. Simulating and analyzing of the 345 kV line examples provided in authoritative literature, and it compares with the calculation results based on traditional standard method and the traveling wave counter method provided by the authoritative literature, this paper verified the validity of the lightning voltage simulation model. This paper establishes an equivalent circuit model for impact transient calculation based on the frequency domain characteristics, represents frequency domain characteristics by a quantitative mathematical, and uses vector matching method for numerical fitting creatively to build a suitable equivalent circuit model in various front time current excitation grounding device, which can be applied to a variety of waving front time current excitation. This paper studies the influence of various factors on the transmission line lightning protection performance counter, and in the light of the various factors it put forward some measures to improve the lightning withstand level of transmission line. The improvement effect of lightning protection measures are quantified, and the weight of each influence factor on the lightning withstand level are divided, so that this paper can choose the most ideal collocation of lightning protection measures.