Preliminary Laboratory Tests on RTV-Coated Insulators Removed from Service

Transmission overhead power lines transport large amounts of electrical energy and consist of HV power conductors, poles, and strings of insulators that connect the earthed poles to the active conductors. These systems are typically designed to have an expected life of 50 years. Therefore, understanding the ageing phenomena related to operating conditions and environmental factors is fundamental to preventing faults, which could have severe consequences. In this regard, the present work investigates the ageing phenomena of modern Room Temperature Vulcanized (RTV) silicone-coated glass insulators, which have been used by Transmission System Operators for the past 10-15 years. This paper focuses on the results of preliminary laboratory tests carried out on a set of new and aged RTV insulators. The results provide an assessment of electrical characteristics in terms of AC flashover voltage and AC leakage current. Additionally, the study examines how the measured feature decay, due to operational and environmental conditions, varies depending on the location of the insulators in the string.