Study On Partial Discharge Characteristics Of GIS Typical Defect Model Under AC And DC Voltage

Partial discharge is one of the main causes of Gas Insulated Switchgear (GIS) insulation degradation. Research on the typical partial discharge characteristics of GIS devices under AC and DC condition could provide theoretical bases for the insulation performance evaluation and insulation structure design and improve equipments reliability and service life cycle. It has major significance for power system stable operation.This paper dissertates the basic theory and analysis methods of of partial discharge signal characteristics under AC and DC condition. The emphasis is on analysis of the following several aspects:characteristics of partial discharge maps, characteristic parameter, discharge response and approximately linear relationship between discharge repetition rate and withstand voltage. In addition, the paper also discusses about the DC partial discharge detection methods uses the AC methods and points out special partial discharges characteristics under the DC voltage. With a experimental detection system foundation, the partial discharge detection and analysis data of two common and representative typical insulation defects model in GIS operation are obtained. The experimental results of needle defect model and metal spherical particle defect model show that the larger diameter or length value of defect models have, the lower voltage partial discharge occurs required. Discharge phase distribution have obvious differences between the needle defect model and metal spherical particle defect model under the AC voltage and discharge phenomenon of spherical particle defect model is not as intense needle defect model’s. Under positive polarity DC voltage discharge initiation voltage is the lowest and metal spherical particle has the most sensitive electric field take-off. Two defect model types with different sizes under equal DC voltage level, the positive discharge density is greater than the negative discharge density.The partial discharge characteristics of typical defects models under AC and DC could be identified through comprehensive analysis of discharge characteristics and each main parameter statistics, thus theoretical and experimental basis in further study about basis partial discharge of common typical insulation defects in GIS equipment are provided.