Study On Shielding Failure Characteristics Of 220kV Multi-Circuit Transmission Lines On The Same Tower

Lightning is an inherent phenomenon in nature.Lightning strike transmission lines seriously endanger the stable operation of the power system,so lightning protection is critical.With the prosperity and development of China's social economy,the land utilization rate is getting higher and higher,and improving the utilization rate of the line and stabilizing the continuous power supply has become a problem to be solved.According to long-term operation experience,the probability of twin-circuit and Multi-circuit Transmission Lines with the same tower having more loops,longer spacing,higher pole and tower and being subjected to shielding failure is higher and higher.The main reason for lightning trip-out of UHV and hybrid double-voltage lines is shielding failure.Therefore,accurate evaluation of the lightning level of the line is of great significance for guiding the safe and stable operation of the transmission line.Electrical Geometry Model?EGM?is the most important method to calculate the transmission characteristics of transmission lines.This method can link the lightning parameters of the lightning to the performance of the lightning through the geometric parameters of the line.The calculation results are closer to the lines.The situation is therefore of certain accuracy.However,the traditional EGM model only considers lightning as vertical downward by using the average height of the conductor,so as to estimate the shielding failure performance of transmission lines,it will produce large errors.In this paper,the direction of lightning strike is extended to[?/2,?_max]by using the improved electrical geometry model.By calculating the projection of the exposed arc and shielding arc on the ground at different lightning incidence angles,the shielding trip probability is obtained according to the probability distribution of the pilot incidence angle.In this paper,a three-dimensional electrical geometry model is introduced to extend the bare arc surface of transmission line in three dimensions.The change of shielding trip rate along the length of each section of the line and the tower is calculated.The final shielding trip rate is obtained by integrating along the direction of the shied.Finally,the accuracy of the calculation is verified by the calculation of the example and comparison with other literatures.The three-dimensional electrical geometric model considering the incident angle of lightning is used to calculate the grounding trip angles under different ground inclination angles,protection angles,tower heights and cross-arm lengths of the single tower,double and four transmission lines on the same tower,and analyze various factors for the tripping of the bypass.The impact of the rate and recommendations for lightning protection.Finally,the risk assessment of lightning protection for 220kV transmission lines in TONGHUA area is carried out,and then the modification scheme of lightning protection and lightning protection is given.