Loss and Recovery of Hydrophobicity of EPDM Insulators in Simulated Arid Desert Environment

Electrical insulators form a very important component of high voltage electric power networks. Along with the traditional insulators i.e. glass and porcelain, etc. presently the polymeric insulators are also used world widely. These polymeric insulators are very sensitive to various environmental parameters such temperature, environmental pollution, UV-radiations, etc. which seriously effect their electrical, chemical and hydrophobic properties. The UV radiation level in the central region of Saudi Arabia is high as compared to the IEC standard for the accelerated aging of the composite insulators. Commonly used suspension type of composite EPDM (ethylene propylene diene monomer) insulator was subjected to accelerated stress aging as per modified IEC standard simulating the inland arid desert's atmospheric condition and also as per IEC-61109 standard. The hydrophobic characteristics were studied by measuring the contact angle along the insulator surface before and after the accelerated aging of the samples. It was found that EPDM insulator loses it hydrophobic properties more proportional to the intensity of UV radiations and its rate of recovery is very low as compared to Silicone Rubber insulator. The effect of water salinity and drop size on the contact angle characteristics was also investigated.