Degradation Studies on Polymeric Insulators used for EHV and UHV Transmission

Abstract

High voltage insulators used in overhead power transmission systems are of key im- portance for safe, reliable, and effcient operation of transmission line in transferring huge amount of electrical power. Conventionally, ceramic/ glass insulators were used in electri- cal power transmission, recently composite/ polymeric insulators are being used in over- head transmission lines. The polymeric insulators offer numerous promising advantages over conventional insulators such as light weight, higher impact strength, better pollution performance, resistance to vandalism due to its slim design etc. Moreover, the inherent property of polymeric insulators of being hydrophobic make it more advantageous over conventional insulators. However, the polymeric material being organic in nature, un- dergo degradation due to different stresses such as environmental stresses (thermal, UV, moisture, fog etc,), and electrical stresses. Further, the presence of electrical discharges such as corona, surface scintillations, occurrence of dry band arcing, operation in adverse conditions, etc., are recognized as the major accelerating factors for material degrada- tion. Presence of heavy ionic deposition over the surface leads to surface discharges and localized temperature rise leads to material erosion which results in electrical tracking formation and eventually leads to ash-over/ line outage of power transmission. In the present work, silicone rubber based polymeric insulators are experimentally in- vestigated for their material properties and long-term service performance. The available literature show that polymeric insulators are quite sensitive to their local environmental conditions and their long-term performance depends on field service environment. The material properties get affected in adverse environment and foul weather condition. The unavoidable service conditions such as moisture, fog, acidic rain, snow, pollution etc., alter their service life by accelerating their aging which directly affect their long-term perform...