Efficient Lightning Protection of a Gas Insulated Substation Replacing an Air-Insulated Substation

Abstract

This contribution highlights a procedure that aims at assessing the different possibilities to improve the lightning performance of an overhead line, connected to a substation that will be transformed from air- to gas-insulated. Therefore, the probability of a shielding failure was first calculated for each span width, using the simplified electro-geometrical model. Then, the overvoltages arising from these shielding failures were calculated using transient simulations. Special attention was paid to the implementation of the dynamic flashover characteristics of the insulators as well as corona-damping effects, as they will significantly influence the outcome of the calculations. It was found that both, a reinforced ground wire protection as well as the installation of line surge arresters at the first tower can drastically reduce the probability of overvoltages within the GIS. If the first option is chosen, an efficient length can be chosen with the help of the calculated probability density functions, sorted after the point of origin of the lighting strike.