Evaluation of Long-term Performance of Composite Insulators for ±400kV Overhead Line on Tibet Plateau

The long-term performance of composite suspension insulators for a DC +/- 400kV overhead transmission line was evaluated after 6-year field operation on Tibet Plateau with high altitude and strong UV radiation. The study was performed under laboratory conditions. The overall electrical and mechanical performances of insulator were tested according to IEC 61109 after visual inspections and hydrophobicity class measurements. Thereafter, the mechanical strength and dielectric strength of high temperature vulcanized silicone rubber (HTV-SR) sheds were examined; furthermore, physicochemical analyses were conducted on the shed specimens. The results showed that the SR shed represented a very slight decrease in hydrophobicity, tensile strength, elongation at break, dielectric strength and have a stable chemical structure. It was demonstrated that the composite insulator with advanced HTV-SR sheath has long-term lifetime even operated under the extremely environmental stresses.