Reproduction and Analysis of Decay-Like Aging Development Induced by Interfacial Discharge in Composite Insulators

In the last decade, the decay-like aging phenomena of fiber-reinforced plastic (FRP) core rods in composite insulators appeared frequently and have significantly affected the safety of power transmission lines. However, the mechanism of its occurrence and development is still unclear. In this work, a method based on rod-housing interfacial discharge is proposed to artificially reproduce the occurrence and development of decay-like aging in FRP core rods under laboratory conditions. The aging process is explored under a high-humidity environment, where high-acidity and high-temperature conditions are also provided by interfacial discharge. The micro- and macroscopic structures, physicochemical properties, and leakage currents of FRP samples are characterized during a 1000-h aging process. The laboratory aged samples resemble the decay-like phenomena in on-site insulators, indicating the effectiveness of this method. Experimental results show that interfacial discharge can trigger the decomposition of epoxy resin in FRP core rods, leading to exposure of glass fibers. Electrical erosion slows down as aging time increases, and the erosion rate is positively related to the porosity of core rods. Further discussion indicates that erosion is impeded by glass fibers in the surface aging layer due to its high thermal and chemical stability, and a three-stage erosion process model is proposed. Finally, a semiempirical model is proposed to describe this aging process, in which the influence of core rod porosity is taken into account. This work provides an effective laboratorial method to reproduce the decay-like aging of composite insulators and reveals its erosion process and the underlying mechanism.