Study On Corona Characteristics Carised By Lightning Strike And Its Influence On High Voltage Distribution Lines

In designing lightning insulation margin of substation equipment, the attenuation and distortion of intruding wave caused by Corona in the transmission lines is neglected, thus making too strict insulation requirements on the electrical equipment, it necessary to study the Corona effect of AC transmission lines. In this paper, based on the analysis of the Q-V characteristics of impulse corona, using the simulation software ATP-EMTP established a dynamic model of impulse corona and its lightning transmission line model, analysis the Corona effect impact on lightning overvoltage wave in transmission line when transmission line strike by lightning with strike back. The simulate results of this model is consistent with the reality. The main results are as follows:(1)Based on the basic concepts and assumptions of Corona, the transmission line equations considering Corona are deduced, based on the Q-V characteristics, established mathematic model of impulse corona. On this basis established the dynamic model of impulse corona by using custom modules in the ATP.(2) With the model of lightning strike transmission line when consider the Corona effect in the ground line found that if regardless of Corona effects, the amplitude of voltages are increased by 33%, and 65% and 88% respectively compared with considering Corona effect when distance lightning at points 100m, and 200m, and 300m respectively; With the impact of Corona effect, the rise-time from original of 3.1μs, and 4.0μs, and 4.4μs increases to 5.2μs, and 6.8μs and 7.9μs respectively, the amplification for 68%, and 70%, and 79% respectively. Corona effect not only elongated the rise-time of lightning wave but also reducing the peak of lightning wave. It can be said that the wave occurred attenuation and distortion, the distance from lightning strike point and measuring point is longer and the more severe distortion the wave happened.(3) With the model of lightning strike transmission line when consider the Corona effect in the phase line found that with amplitude of 1 OOkA lightning current strike 1000kV AC transmission line, if regardless of Corona effects, the amplitude of voltages are increased by 34%, and 41% and 57% respectively compared with considering Corona effect when distance lightning at points 100m, and 200m, and 300m respectively; The distance from lightning strike point and measuring point is 300m, considering Corona effect the amplitude of voltage is 1098kV, without considering Corona effect the amplitude of voltage is 1720kV, the difference between the two is 622kV.This improves the lightning withstand level of transmission line indirectly, it’s beneficial for transmission line lightning protection.(4) By simulating the different cases of lightning current waveform Corona effect on the lightning stroke of lightning overvoltage on power transmission lines found that the longer half peak time the lightning current waveform have, the corona effect on lightning overvoltage wave of the greater the degree of influence.(5)In the case of only change the tower grounding resistance, when transmission line or ground line direct strike by lightning and back flashover happened, with the tower grounding resistance is greater, the corona effect on lightning overvoltage wave of the greater the degree of influence, the areas of higher soil resistivity should consider the influence of Corona, which is good for lightning protection of transmission line.