Study on Lightning Surge of Overhead Line-GIL Hybrid Line

Gas-insulated transmission line (GIL) has a high risk of lightning overvoltage as it is usually connected to exposed overhead line. The transient models of hybrid transmission system, including overhead line, GIL, transmission tower, insulator string and lightning arresters, etc., have been developed in EMTP environment, and sensitivity analysis, such as the lightning impulse waveform, lightning strike location, shielding failure or back flashover on lightning surges, have been performed in this research. Lightning arrester is one of the most effective measures to suppress overvoltage, and there are two lightning arrester schemes proposed in our work. The results of the study show that the installation of lightning arresters at the terminals of the GIL does not guarantee the lightning surge withstand level of the GIL. The joint, GIL and terminals of the overhead line, where the line lightning arrester must be installed, which is necessary for GIL operation.