Research On Factors Influencing Lightning Withstanding Level Of Transmission Line In Heaviliy Lightning Areas

Long term operation statistical results showed that trip accident due to lightning striking occupies a large percentage of all transmission line accidents. With the construction of power grid turning for Extra High Voltage (EHV) in china, using four-circuit lines on the same tower is an inevitable trend. So it has important scientific meaning and practical value for researching lightning withstanding level of 220kV four-circuit lines on the same tower.First, this thesis analyzes lightning activity in Hui-Zhou region. Aim at lightning protection question of the Hui-Zhou 220kV four-circuit lines on the same tower, the PSCAD/EMTDC simulation model used for investigating the back stroking lightning withstanding level of transmission line was built. The flashover model of insulators which considered the wave tail flashover situation makes up for the shortcomings of traditional intersecting method. Multi-wave impedance model of tower can truly reflect the spreading course of lightning current on the tower. The new way of the differentiation of shielding failure and back flashover is presented based on the different the principle of lightning striking the tower top and conductor, which was verified by PSCAD/EMTDC simulation model. The results show that this method is simple and fast, which can accurately distinguish the form of lightning.At last, by calculating and analyzing various of factors that affect the lightning withstanding level of 220kV four-circuit lines on the same tower based on the back strike simulation model and the improved electric-geometry model (EGM). We can draw the conclusions: the result by intersecting method is more accord with the practical circumstance than that by existing standard methods. Reducing the footing resistance is one of the most efficienct methods to reduce the back stroking lightning withstanding level of single-circuit and multi-circuit transmission lines. The height of tower on the impact of the lightning withstanding level is also evident. The conductors should be used reverse phase sequence. Installing two sets of arresters is best in the top, and the program of installing arresters at the upper three-phase is still a considerable effect. Ground obliquity is the main factor that affects the maximum of the shielding failure lightning withstand level. When the ground obliquity. increases, the shielding failure lightning withstand level will increase nonlinearly. The lower the tower is, the higher lightning withstand level of four-circuit lines on the same tower will be. These results will propose reference for the same type of transmission line.