Reasons For Insulators Losing Their Hydrophobicity

When operating under heavy loads, the electric field strength on the overhead power line insulators surface increases significantly. High-voltage discharge accelerates the volatilization of low molecular weight substances (LMWs) in the silicone rubber surface layer; these small organosilicon molecules originally contributed to the material's hydrophobic properties. Electro-aging causes the Si-O-Si main chain to break, and the content of methyl groups in the side chains to decrease, making the material surface more polar and thus reducing hydrophobicity.

Heavy loads also lead to increased heat generation and rising internal temperature in the tension insulator material. Under the combined effects of high temperature and high humidity, the microstructure of the silicone rubber surface deteriorates—cracks and pores increase, and the surface becomes rough and uneven. These microscopic defects alter the contact characteristics between water droplets and the material surface, making water droplets easier to wet and adhere to, and the hydrophobicity grade gradually decreases from HC5 to HC4 or even lower.