Premature Insulator Failure: Latent Damage Mechanisms Under Environmental And Electrical Stress
In long-term observation of power system operation, premature degradation of suspension composite insulator performance has become a major challenge for power grid maintenance personnel. Some outdoor composite suspension insulator units experience a significant drop in insulation resistance after only a few years of operation, sometimes even having to be taken out of service before reaching half their designed lifespan. Behind this phenomenon lie a variety of complex physicochemical mechanisms.
Environmental Stress and Material Aging
polymer suspension insulator is exposed to industrial pollution, salt spray, and ultraviolet radiation for extended periods. Strong ultraviolet radiation directly attacks the molecular backbone of silicone rubber, causing the Si-O-Si bonds to break. The combined effect of salt spray and moisture in coastal areas forms a conductive electrolytic layer on the suspension type insulator surface. The continuous flow of leakage current triggers electrolytic erosion of the material, resulting in irreversible hardening and cracking on the surface. Fourier transform infrared spectroscopy (FTIR) analysis confirms that a large amount of hydrophobic side chains are lost on the aged composite tension insulator surface, causing the material to transform from hydrophobic to hydrophilic and lose its original anti-flashover capability.
Electrical Stress and Interface Damage
The uneven electric field distribution at the high-voltage end accelerates the degradation process of high voltage transmission line insulators. Under strong electric fields, microcracks develop in the glass fibers at the core-sheath interface, and the epoxy resin matrix gradually decomposes. Ozone and nitrogen oxides generated by partial discharge cause secondary corrosion of the material. As operating time increases, the surface insulation resistance of the overhead power line insulators drops sharply from the GΩ level to the MΩ level, and the significant reduction in self-breakdown voltage directly threatens line safety. These changes in microstructure ultimately manifest as macroscopic insulation failure.
