Simulated calculation and analysis of lightning performance of UHV A.C. transmission line

Lightning stroke is the key problem for safe operation of UHV transmission line. Because of the large scale of the tower and the high operation AC voltage, the shielding design of tower became one of the most important aspects of the UHV transmission line design. This paper was based on the typical towers of China 1000 kV AC transmission line: waist-type single-circuit tower, cup-shape single-circuit tower and double-circuit tower. The lightning protection performance of all the three towers was calculated and analyzed with EGM and EMTP. The results show that the cup-shape tower performs best in the prevention of lightning shield failure while the waist-type tower performs worst. And in the prevention from back flashover, the lightning trip-out rate of the double-circuit tower is much bigger than waist-type tower and cup-shape tower, mostly because of its larger height. The lightning stroke trip-out rate of the three types of typical towers for 1000 kV transmission line were compared under different shield angles, ground slope angles and ground resistance. The results also indicate that the trip-out rate of all these types of UHV towers will rise obviously as the shield angle or ground slope angle gets larger.