Design Of Surface Charge Test And Measurement System Of Insulator At Gas-Solid Interface

With the improvement of transmission voltage levels in recent decades, the insulation materials have to sustain much higher electric field strength. Surface charge can accumulate on insulator surface at the gas-solid interface under the stress of high voltage, especially in the high voltage Gas-Insulation-Switchgear, since in such kind of apparatus the support insulator endures unidirectional voltage perennially. Surface charge accumulated on insulator can lead to local electric field enhancement and sometimes can result in abnormal flashover of the insulator. Therefore, it is very important to study the phenomena of surface charge accumulation for improving the dielectrics properties and insulating performance of insulator.There are various factors which affect the surface charge accumulation, such as the shape and material of insulator, the waveform, magnitude and polarity of the voltage, the configuration of electrode, and the humidity of gases and so on. The larger the relative dielectric constant of insulator is, more serious the surface charge accumulation is. The higher the voltage magnitude is, the more prone the surface charge is to accumulate.In the field of electrical insulation research, the surface charge measurement of insulator belongs to the category of electrostatic measurement, so it can not be done with conventional measurement techniques. On the base of previous research the electrostatic probe is improved in the present paper and the analytic results show that the electrostatic probe designed in this thesis has the properties of high resolution. In order to investigate the mechanism of surface charge accumulation and its effect on flashover characteristics of the insulator at the gas-solid interface, the paper designs a DC and impulse high-voltage generator, and the surface charge measurement system is also presented in the research. The electric field on the surface of insulator is also simulated using the finite element analysis software and the mechanism of surface charge accumulation is studied based on the simulation. The results show though various factors can affect surface charge accumulation, normal-field strength on the surface of insulator is the essential factor for the deposition of surface charges at the interface of gas-solid dielectrics. Under the same experimental conditions, sometimes the maximum value of accumulated surface charge along the insulator are different; the conductive surface coating can prevents the surface charge accumulation.