Influence of Gas-Insulated Transmission Line (GIL) on Energization Overvoltage

Energization overvoltage is very important for security and stability of power grid, and it also provides reasonable reference for insulation coordination. This article proposes the influence of GIL on energization overvoltage. Parameter characteristics for GIL are presented and analyzed in detail, which are different from that of overhead line (OHL). Thus, with GIL applied to transmission system, the traditional methods for analysis of energization overvoltage could not be used. However, amplitude of energization overvoltage and voltage attenuation speed can be simply discussed only for a fully-GIL or a fully-OHL. Analysis on how the length, ratio and location of GIL effect the energization overvoltage, need to be obtained based on simulation results. The study includes various sensitivity analyses to find out the impact of transmission line parameters on overvoltage. By the statistical analysis, it has been discovered that energization overvoltage of a hybrid OHL-GIL circuit are lower than those of a fully-OHL circuit with the same transmission lengths. There is no evident changing regularity of overvoltage in different locations of GIL. The attenuation speed of a hybrid OHL-GIL circuit is lower than those of a fully-OHL and fully-GIL.