Condition Monitoring of High Voltage Composite Insulators: Recent Trends and Findings

Composite insulators with polymeric housing are been increasingly used over porcelain and glass insulators in outdoor high voltage insulation structures due to some specific advantages such as light weight, high mechanical strength and better contamination resistance. Among several other used housing material silicone rubber (SIR) is highly preferred for electric power transmission networks operating at an extra-high voltage (EHV) and ultra-high voltage (UHV) levels because of its high hydrophobicity and hydrophobicity transfer capability. However, being organic in nature, polymeric housings degrade gradually with time and accessing their long-term service performance is a big issue. In general, twelve parameters are being identified by CIGRE WG D1-14 to access the health of polymeric insulating material and standardized test methods for accessing eight properties have already been specified. Therefore, this work comprehensively reports the state of the art with regard to the condition monitoring techniques/test methods being adopted for evaluating remaining four parameters viz. hydrophobicity, the resistance against corona discharge, flammability and UV weathering.