Investigation on Tower Collapses of 500 kV Renshang 5237 Transmission Line Caused by Downburst

In all kinds of natural disasters jeopardizing transmission lines, intense storm is the most minatory one, the accidents and failures in high voltage transmission lines and the damage to transmission towers caused by intense storm occur now and then. The authors firstly present the result of field investigation on the failures that ten towers of 500kV Renshang transmission line 5237 collapsed and the flashover of 500kV Renshang lines 5237 and 5238 of East China power grid occurred, those failures were caused by the downburst which hit Siyang County , Jiangsu province on June 14th, 2005. According to the order of severity of transmission tower collapse, the collapsed towers are classified; the destruction characteristic of downburst and its damage to transmission lines are analyzed. The results of preliminary analysis on the reasons of tower collapses show that the extraordinarily intensive downburst is the principal cause of these failures; the quantity of diaphragms designed according to the current design specification for transmission towers to resist wind is insufficient and the dynamic coupling effects between transmission towers and conductors cannot be neglected.