Study On Differentiation And Lightning Protection Of 500 KV Transmission Line In Hunan Based On Improved Electrical Geometry Model

Lightning strike is one of the important causes of high voltage transmission line fault.With the continuous operation of high-voltage and ultra-high voltage transmission lines,compared with the traditional transmission lines,the lightning failure presents new characteristics:On the one hand,due to the high level of lightning-resistant transmission lines such as high voltage and ultra-high voltage,lightning current The probability of amplitude exceeding this value is very low,and the possibility of counterattack is very small.However,due to the complicated geography of hilly areas with high voltage and extra-high voltage transmission lines,Fault,and then accurate assessment of the transmission line around the trip rate is of great significance on the line lightning protection;the other hand,the transmission line corridor through the mountains,plains,hills and other terrain,due to lightning parameters and the line structure parameters Different,often on the impact performance is also different,to some extent,lightning protection transmission lines are different.Therefore,it is very important to consider the influence of the topography of the line,the structure of the tower and the level of thunder and lightning on the lightning strike performance of the transmission line.The higher the voltage level of the transmission line,the greater the proportion of the bypass trip,so the model of the circle-strike calculation is emphatically studied.At present,transmission lines are often used to analyze the lightning protection performance of the line around the lightning by the method of law,the pilot model and the electrical geometry model(electrical geometry model).The electrical geometry model combines the parameters of line structure and lightning discharge characteristics and puts forward the concept of striking distance,which is widely used in lightning protection calculation of transmission lines.However,in the practical application of the electrical geometric model,the calculation error is larger for the case of smaller lightning current amplitude,negative protection angle and ground inclination.From the aspects of calculation model and other aspects,the electrical geometric model is improved by considering the influence of ground inclination,lightning incident angle and so on.The improved electrical geometric model was used to evaluate the lightning protection.The lightning protection of the 500 kV mountain transmission line was modified.The lightning,topography,tower and other parameters of the transmission line were calculated.Based on the improved electrical geometry model,Shielding the tripping rate,assess the mine risk level and lightning performance,according to the assessment results targeted lightning protection measures to carry out mine transformation.Through the operation example analysis,it proves that the transformation has good technical and economic benefits.Through the improvement of the calculation model of the shielding failure in the differential lightning protection method and the example of the differential lightning protection for a 500kV transmission line,methods and experience guidance are provided to ensure the safety of the transmission line power supply and improve the economy of the lightning protection transformation.