Lightning Performance Evaluation Of Ehvac Transmission Lines Based On Lightning Detection Data

Tower height and width of right of way are increasing with the development of power system, which leads transmission lines exposed to more lightning flashes. Guangdong is a high lightning activity area, where lightning flash is one of the main factors. In order to minimize the loss caused by lightning accidents, it is necessary to study lightning acativities which are of great importance for lightning protection design in a special area and to evaluate the lightning performance of extra-high voltage AC (EHVAC) transmission lines.This paper adopted the lightning detection data in Guangdong province collected by lightning location systems to analyze the lightning acativities. The critical lightning spots of EHVAC transmission lines were found out by developing an electro geometric model (EGM)-based model.1) Spacitial and temporal distributions of thunderstorm days, number of lightning flashes and ground-flash density were examined by Matlab in Guangdong, in the area through which 500kV Nengbo transmission line passes as well as along the right of way of 500kV Nengbo transmission line. The spacitial distributions of lightning acativities were shown in Google Earth (GE). Meanwhile, the relationship between lightning day and ground lightning density had been investigated. Cumulative frequency distributions of peak lightning current were involved.2) The whole line had been divided into multiple statictical sections according to the half separation and minimum distance between two adjacent towers, lightning strike-effect radius. Under each different circumstance lightning stroke number of the segments where each tower belongs to had been calculated.3) Indices had been introduced including lightning stroke frequency, back stroke probability and shielding failure probability, back stroke severity and shielding failure severity, back stroke flashover severity and shielding failure flashover severity, lightning stroke severity to estimate lightning performance of EHVAC transmission lines. Lightning flashover severity was employed to distinguish the critical lightning spots. The impact of line sectioning method on lightning performance evaluation had been studied. Compared with actual lightning faults along Nengbo transmission line with the results calculated by the procedure, the evaluation model showed practical and reliable properties. Therefore it can be considered as a reasonable estimate of lightning performance of EHVAC transmission lines.key words:Lightning Location System; Extra High Voltage Alternative Current; Lightning Performance Evaluation; Electro Geomatric Model; Lightning Strike-Effect Range;Critical Lightning Spots; Lightning Stroke Severity;Lightning Flashover Severity...