Study And Development Of Lightning Risk Assessment System For Transmission Lines

Shielding failure is the main reason of causing lightning trip failure, andmicrotopography is one of the most important factors which affect the shieldingfailure of transmission lines. Therefore, to assess the impact of the microtopographyon the shielding failure of transmission lines accurately mean great scientificsignificance and applied value in engineering. The main contributions of the study inthis paper are as follows:(1) Take a number of vertical shear plane evenly from whthin the lines on bothsides of each tower, then calculate the shielding failure trip rate within each verticalshear planes, which is based on to assess the shielding failure resistance performanceof the transmission line. Take the largest one as the shielding failure trip rate of thistower, The improved model take consideration of changes of the microtopographyalong the line, which accords with the real situation and shows applied value inengineering through examples.(2) Based on Google Earth, this paper researches on the rule of howmicrotopography affects the lightning protection performance. Firstly, this paperintroduces how to form the KML files of transmission line. Secondly, according tothe lightning failure statistic in southern Hebei grid, the affects of microtopographyon lightning selectivity are statistically analyzed. Typical accidents such as farmpond, ridge top, hillsides and valley terrain conditions are analyzed, and the basic lawof how the four kinds of microtopography factors affect the lightning protectionperformance of shielding failure for500kV transmission lines is found(3) Based on C#programming language and the improved model as the kernelalgorithm, a lightning risk assessment system of transmission lines is developed. Thesystem can calculate the shielding failure trip rate of each tower of the500kVtransmission line in a province, draw the distribution curve of the shielding failuretrip rate of each tower within the whole line to assess the shielding failure resistanceperformance of the transmission line, and propose targeted rectification measuresagainst the weak points of the line, to improve shielding level of the transmissionlines.