Research on the adhesiveness between core rod and sheath for composite insulators on the transmission lines

Due to the corrosion problem, there emerge various fracture phenomena for composite insulators on several 500kV AC transmission lines in China, which has caused serious threat to the normal operation of power system. Therefore, it is urgent to analyze the fracture mechanism and propose feasible evaluation method for the failure of composite insulators. In this paper, appearance observation, water diffusion test and dissection test for the fractured 500kV AC composite insulators were carried out, and the results indicated that the main factor that led to the fracture was the bad adhesiveness between core rod and sheath. In view of this, one classification method was proposed to evaluate four operation composite insulators in order to investigate and evaluate the adhesiveness, and the results demonstrated that the adhesiveness was related to not only the bonding quality in production process but also the electric field intensity in operation process. The classification evaluation method was proved to be effective for the adhesiveness between core rod and sheath, which could provide valuable references for the production and maintenance of composite insulators.