Partial Discharge Characteristics of Millimeter Metal Particle on a GIS Insulator Surface Under Long-Term Constant Voltage

It is unavoidable for metal particle to be brought in gas-insulated switchgears (GISs) during the production, installation, and operation of the equipment. Currently, the metal particle is considered as one of the critical factors in insulation failures. In this paper, the partial discharge (PD) test of metal particle on the surface of an actual 220-kV insulator is performed under operation electric field of 1100 kV GIS insulators. Then the discharge characteristics of millimeter particle under a long-term constant voltage are investigated. The experiment result indicates that the PDs of metal particles is intermittent under working condition. In the initial period of the experiment, the discharge level can attain 9 pC, and a maximum of 150 discharges occur per second. Subsequently, when the test voltage keeps unchanged, the discharge level and repetition rate of PDs gradually decrease. Finally, the discharge tends to disappear within 60 min after the voltage application, and then suddenly become intense again briefly when t = 210 min and t = 270 min. The results in this paper gives an important basis for knowing the discharge characteristics of small metal particle well and can help to improve the reliability of GISs.