Study of charge accumulation along the insulator surface in the DC GIL

In order to promote the flexibility of the selection of transmission corridors, the DC gas insulated transmission line (GIL) can be utilized to substitute parts of the overhead line or cable in some special environments. One of the key factors that greatly threaten the insulation level of the DC GIL was the accumulation of surface charges along the supporting insulators. The plane-plane electrode system was established to simulate the electric field distribution of the coaxial cylinder configuration in the GIL. The electric charging mechanism of insulators in the DC GIL, as well as the influence of the insulator's geometry and conductivity of SF6 gas on surface charge accumulation, was investigated. Results show that surface conductivity of the insulator made of PTFE is influenced more greatly than volume conductivity by the electric field. Charge accumulation can be significantly checked when the normal component of the initial field strength along the insulator's surface is small. The polarity of accumulated charges is influenced by the ratio of the gas conductivity and the surface conductivity of insulators.