Analysis of surface charge decay process on insulators in SF₆ and air

The surface of insulators is prone to generate charges under a DC high-voltage for a long time, which has a great impact on insulation performance of the insulators. Surface charges decay by three mechanisms, by volume and surface resistivity of the insulator as well as by neutralization from the gas. To study surface charge decay process on insulators, a set of surface charge measurement device was designed, which could measure the surface charge distribution on insulators in different gases and different air pressures. The insulator which was used during experiments was made of epoxy resin, and the capacitance probe method was used for measurement. The surface charge decay processes were experimentally measured in air at 0.1 MPa and in SF₆ at 0.5 MPa. The experimental results reveal that, the decay process of the surface charge is similar to exponential decay process, and the time constant of the decay rate is 10⁴ s. The rates and mechanisms of charge decay in different environments are discussed in particular. The surface charges mainly decay by volume and surface resistivity of the insulator. The effect of surface charge accumulation on insulators stimulates a wide interest among many countries as the SF₆ gas-insulated is widely applied. The surface of insulators is prone to generate charges under a DC high-voltage for a long time, which has a great impact on insulation performance of the insulators. Surface charges decay by three mechanisms, by volume and surface resistivity of the insulator as well as by neutralization from the gas. To study surface charge decay process on insulators, a set of surface charge measurement device is built, which can measure surface charge distribution on insulators in different gases and different air pressures. The insulator which is used during experiments is made of epoxy resin. The capacitance probe method is used for measurement. The surface charge decay processes are measured by experiments in air, 0.1 MPa and in SF₆, 0.5 MPa. From the experiments results, the decay process of the surface charge is similar to exponential decay process, and the time constant of the decay rate is 10⁴ s. The rates and mechanisms of charge decay in different environments are discussed in particular. The surface charges mainly decay by volume and surface resistivity of the insulator. Also, the results will give some help for the insulator design.