Contents I. Introduction
Epoxy and its composite materials have been widely used in power devices worldwide for several decades [1]. Owing to the manifold advantages encompassing outstanding dielectric properties, corrosion resistance, and thermal stability, epoxy composites play a pivotal role as essential insulating materials in basin insulators designed to provide support for high-voltage conductors and to isolate different gas chambers in the enclosed and compacted environment of gas-insulated switchgear (GIS) [2], [3], [4]. Nevertheless, aging concerns have persisted since the adoption of polymeric insulation materials in high-voltage equipment. And insulation degradation remains a significant apprehension, particularly for GIS systems undergoing prolonged operation [5]. Currently, the initial set of GIS insulators in China, constructed around the 1980s, has been in operation for close to or even exceeding the initially designed operational life, typically considered as 30 years. The question of whether to perform maintenance, bulk replacement, or opt for an extensive replacement incurring substantial costs is a matter under consideration. There is an urgent requirement to study the aging characteristics and aging state assessment of the epoxy composites, considering both the equipment safety of GIS and the economic reason.
