Research On Characteristics Of Surface Charge Accumulation Of Basin Insulator

Gas Insulated Transmission Line has many advantages in practice,with high transmission power,low accident rates and less pollution to the environment,which has led to a gradual increase in its use in recent years.When the central conductor of a gas-insulated transmission line is energised with DC voltage,a charge builds up on the surface of the basin insulators connected between the conductors,which causes a sudden change in the electric field on the surface of the basin insulators and a reduction in the insulator flashover voltage,resulting in the failure of the insulated line to operate properly.It is therefore of great practical importance to investigate the charge build-up characteristics on the surface of basin insulators under DC power.In this thesis,a surface charge test device for basin insulator shrinkage model specimens is manufactured.This device simulates the operating environment of basin insulators in a gas-insulated transmission line and measures the charge build-up afterwards,and analyses the influencing factors of surface charge build-up from the test results.The device consists of six main components:the GIL（gas-insulated transmission line）test tank,the robotic arm system,the motion control system,the measurement system and the data storage system.The GIL test tank simulates the actual operating environment of a gas pipeline.The motion control system and the robotic arm system work in conjunction with each other to automatically complete the measurement of the surface charge.A data storage system allows the potential data to be stored.The surface charge test device was used to experimentally investigate the factors affecting the build-up of surface charge.The test results show that an increase in pressurisation time and voltage amplitude leads to an increase in the amount of charge built up on the surface of the insulator model specimen,that different polarities of the power supply lead to different polarities of charge,and that the amount of charge built up on the surface of the insulator model specimen decreases when the gas pressure increases.The simulation analysis of the electric field of the actual 252kV basin insulator shows that the electric field of both convex and concave surfaces tends to increase and then decrease along the radial direction,and the electric field strength of the convex surface is higher than that of the concave surface,but the electric field strength of the concave surface is slightly higher in the area near the central guide rod.Finally,a simulation analysis of the charge accumulation effect on the surface of the basin insulator shows that when there is charge accumulation on the surface of the basin insulator,the electric field strength increases at the location of the accumulation and decreases in the vicinity of the location.When negative charges accumulate at the same location on the surface of the basin insulator,the electric field strength at the accumulation location decreases and the electric field strength near the location increases.When different densities of charge accumulate on the surface of the basin insulator,when the line charge density is 2.7×10^-6c/m,it is the same as the original electric field distribution,and the value of the surface charge density that does not affect the insulation performance can be calculated by this method.