Calculation And Analysis On Shieding Failure Of 500 KV Single Circuit Transmission Line Around The Lightning Strike Are

In recent years, lightning stroke is one of the important causes of the accidents that occur on transmission lines. With the increase of voltage grade of transmission line, the proportion of outages because of shielding failure also increases. Therefore, exactly evaluating lightning-withstanding level and shielding failure flashover rate (SFFOR) of transmission line, is especially important for system service and stable operation.At present, the main methods to evaluate the characteristic of shielding failure for transmission line are the standard method, leader progression model(LPM)and electric geometry model(EGM).The electric geometric method relates the lightning discharging characteristic with structural dimension of transmission line together, and"striking distance"is introduced to describe the object's lightning attracting ability. It is much more advanced than the traditional method. Therefore, the electrical geometry model (EGM) is used as the foundation method to study on transmission lines and the buildings around the protection of lightning strike is mainly by at present.Because EGM is a engineering calculation model that based on the field observation data of the lightning strike. So designing the lightning protection shielding of the transmission line , we also need to accumulate the operation experience.In view of this reason, as people gain more knowledge about long air clearance discharge and lightning stroke discharge, Eriksson, Dellera and Rizk used the recent research results of long air clearance discharge in the study on shielding failure flashover and proposed the leading progression model (LPM). Actually leading progression model is the further development of the EGM, it said: in the downward leader role, objects on ground produced would produce and extent the upward leader which encounter the downward leader at last. This encounter made the decisive role in shielding failure flashover. The paper bases on the basic ideas of electrical geometry model and studied on east China power grid single loop transmission lines. The calculation method of both A-W electrical geometry model and the leading progression model would be strong explored in paper. A-W electrical geometry model and would be built. Especially important parameters of these two models would be deduced in detail. AWEGM method would be used in studying LuoFei 500 kV line to find out the highest shielding failure flashover rate of one pole in whole line and the leading progression model would be used in studying LuoFan 500 kV line to calculate shielding failure flashover rate of line. Establish all kinds of parameters in the two models, especially to determine formula of striking distance. On the basis of these records, some important relative aspects would make inflection on shielding failure flashover rate and some kinds of measures would be given to strengthen the lightning protection performance.