Development of the water drop–induced corona test method for composite insulators

Historically, line composite insulators have been used with success in relatively clean environments mainly due to the simplicity of handling and better pricing than ceramic insulators. Voltage upgrading and compact design of overhead lines are new typical nisch areas for composite insulators. Hydrophobicity is a key parameter of composite insulators providing insulation performance much higher than ceramic insulators. However, the outstanding hydrophobic properties of composite insulators may be deteriorated not only due to dry-band activity in polluted areas but also due to continuous corona activity on the housing material itself or corona from the metal parts (fitting, grading/ corona ring) onto the housing. In the worst case the insulator may suffer from erosion and other damages [1]. This puts higher importance on protecting the insulator from long-term aging.