The Lighting Overvoltage Analysis Of500kV Transmission Lines

As an important part of the power system, the safe operation of the transmission lines is the premise and guarantee to the power system stability. The lightning discharge phenomenon is common in nature, and lightning is one of the important reasons caused transmission line faults. With the improvement of the voltage level of the power system, the transmission line faults caused by lightning overvoltage incidents has occurred. Therefore, in-depth study in the characteristics of the transmission line faults caused by lightning impulse,the analysis on lightning withstand level of transmission lines accurately identify effect items around strike lightning over-voltage,or counterattack lightning over-voltage, targeted to take protective measures for reducing the rate of transmission lines trip is very important.In this paper, using ATP/EMTP,a common electromagnetic transient simulation program, simulated500kV transmission line being struck by lightning, according to the latest research results in the world, build a model of the line in lightning condition. The model includes the lightning current model, transmission line tower model, string insulator flashover model. Creating lightning model, in order to simulate lightning overvoltages on real analog line, take full account of wave propagation attenuation and distortion produced by lightning impact corona,and working voltage is exist when lightning in transmission lines.Characteristics of line back detour overvoltage or counter overvoltage in considering or ignoring the impact corona on transmission line is developed. Both of the waveform will be attenuated and oscillated, but the attenuation of back detour overvoltage is slightly lower than counter overvoltage. Change the parameters of the lightning current, the influence of the two probability occurrence of lightning overvoltage on the500kv transmission line is discussed. Based on the fact that voltage with50Hz power frequency is exist when the line be striking, through the simulation its influence on lightning overvoltage is calculated.Lightning over-voltage due to lightning current waveform and amplitude, wire and lightning line layout, grounding resistance and other factors have an impact, ATP/EMTP software to study these factors change around the strike and counter the impact of the voltage. The same time, according to the established simulation model to analyze the counter-attack, around the strike, lightning overvoltage transient characteristics not fault the three cases, and comparative analysis of whether or not in accordance to consider the impact of the corona, find out the lightning strike the top of the tower and wires the overvoltage characteristics of these two cases both ends of the insulator string voltage waveform characteristics and overhead wires, lightning line. The results of this study lightning overvoltage transmission line research laid the theoretical foundation, to raise the level of the existing transmission line lightning protection and provide a reference of lightning protection of new lines design.