Abstract:Gas-insulated transmission line (GIL) has many advantages, such as large transmission capacity, small occupation of land, small maintenance and small environmental impact, and has gradually become the first choice to replace overhead lines in special environments. Aiming at a hybrid transmission line system with two 500 kV overhead lines partially reformed to GIL, a GIL-overhead line hybrid transmission line model is established in PSCAD based on the structure and electrical parameters of GIL and overhead line, and short-circuit faults are set up at different positions of the line for simulation, so as to study the differences between fault characteristics. And suggestions for line reconstruction are proposed based on the simulation results.