Research On The Lightning Shielding Failure And The Electromagnetic Transient Of The UHVAC Transmission Lines

Ultra-high voltage (UHV) transmission lines is the trend for the development of the bulk power transfer technology, which features in its large transmission capacity, long transmission distance, low power loss, narrow corridor and savings in investment. The probability of lightning strike because of long distance and high tower height also increases. With the transmission capacity increasing, the internal overvoltage becomes more severely because of capacity effect of transmission lines. Therefore, research on the lightning shielding failure and the electromagnetic transient of the ultra-high voltage transmission lines, is especially important for UHV transmission lines service and stable operation. First of all, based on the improved electric geometry model, a method from the three-dimensional is presented to determine shielding failure rate. The method obtains area of exposure curved surface and protecting curved surface with the height of the conduct wires as variable. By means of ratio to real practical area, the formula about lightning shielding failure rate of whole span on transmission lines is obtained. The calculation result of an example shows that the formula is workable. The influences of lightning strike angle, ground obliquity, and angle of protection to shielding failure rate are discussed, some measures are discussed to reduce lightning shielding failure rate of Ultra-high voltage transmission lines. Secondly, according to the electromagnetism field theory, striking distance factor model considering the height of tower and working voltage is established. On the base of the model, the variations of striking distance factor and lightning shielding failure rate are analyzed by using the numerical simulation. The calculation results show that the striking distance will certainly be dissimilar between that of leading lightning to the shield conduct wire and that of leading lightning to the conduct wire when analysis shielding failure rate of ultra-high voltage transmission lines is based on electric geometry model. At last, the article based on the example of 1000kV ChangZhi-JingMen ultra-high voltage transmission line, the study of comprehensive simulation is carried out about fundamental frequency overvoltage, secondary arc current and recovery voltage. Moreover, the influences of the line arrangement, line structure, and arc resistance on the secondary arc current are analyzed.