HVDC pollution testing of insulation: experience from service, laboratory and test station

The need for testing at HVDC and UHVDC levels has increased dramatically over the last few years. Typically test objects include valves, cables, line insulators, cable accessories, optical instrument transformers and station post insulators. Some of these tests are dielectric tests and in many cases the tests include also pollution testing, which is a main dimensioning parameter for outdoor insulation in DC. This publication focuses on the experience that STRI has gained throughout years of investigating and testing insulators under HVDC in polluted conditions. Examples from service and field stations and laboratory investigations of artificially and naturally polluted ceramic and polymeric insulators are presented. Examples of practical implementation of laboratory results in design practice are also given.