Analysis of Electrical and Physicochemical Properties of GIS Spacer with Long-term Service

The aging of insulation materials in GIS leads to a series of electrical problems. As a fully enclosed device, GIS faces extremely complex repairing problems once an accident occurs comparing with the separated open equipment. The root cause of this problem is multifaceted, including not only the high voltage issues, but also the environmental factors in operation such as temperature, mechanical vibration, etc. All these lead to the aging of insulation materials and the failure of the equipment. Therefore, it is important to analyze the aging state of the GIS spacer, especially the GIS spacers in service. In this paper, to evaluate the aging state of the GIS spacer in service, the structural properties, as well as electrical performance of insulating material obtained from a GIS spacer served more than 15 years are characterized and compared with that of a new GIS spacer. To investigate the change in electrical properties, dielectric loss test, polarization current, surface resistance, and partial discharge measurement are delivered. And thermal characterizations including DSC, TGA and IR are also delivered to investigate the structure change of the insulation epoxy. The results show that the aging effect reduces the surface resistances and increases the dielectric loss, polarization current and partial discharge. And with the service time increases, the glass transition temperature and the thermal decomposition temperature of the GIS spacer declines.