Surface Charge Accumulation Characteristics of Cone-shape Insulator Under DC/AC

In order to investigate the charge accumulation characteristics of a basin-type insulator in GIL under DC and AC voltages, a downsized cone-shape insulator of epoxy material was designed. Based on the electrostatic probe method, the surface potential of insulator was measured, and the charge distribution was obtained by a charge inversion algorithm. Moreover, the law of charge accumulation characteristics and transformation under DC and AC voltages were analyzed, and a method of extracting the phase of AC voltage truncation time was also proposed. The relationship between charge distribution and the development of AC voltage can be obtained by combining the macroscopic measurement results with the microscopic discharge process. It is shown that, in this coaxial electrode configuration, the charge accumulation on insulator surface is mainly caused by bulk current under DC voltage, while it is caused by partial discharge under AC voltage. Under DC voltage, the charge polarity is the same as the applied voltage, and the surface charge density is mainly affected by the voltage amplitude and applying time of voltage. However, the charge polarity under AC voltage is related to the phase of voltage truncation moment. The surface charge density is affected by repeated neutralization between positive and negative charges, and its value is about two to three orders of magnitude smaller than that under the DC voltage. © 2019, High Voltage Engineering Editorial Department of CEPRI. All right reserved.