Failure Investigation on Field Aged Porcelain Suspension Insulators

A specific type of cap and pin suspension insulator has resulted in a number of pole fires while in service. To identify the underlying failure mechanism, electrical, mechanical, and material quality tests were performed. Despite appearing visually in good condition, and retaining higher than required mechanical strength, some samples were highly conductive at relatively low voltages. Porosity tests, resistance, power factor, and partial discharge measurements were inconclusive in defining the cause of failure prompting further investigation.