Equipment for on-site testing of HV insulation

On-site testing has often been requested by the utilities following installation of new HV cables and also to check the condition of HV power transformers suspected of a damaged insulation. Specialized equipment for on-site tests has to withstand off-road transportation, to pass under road-bridges, be equipped with its own power source, and what is most difficult, to make measurements at HV substations which are notorious for intense electromagnetic interference. At present a HV resonant test set-up with the partial discharge (PD) measuring instrument and the C-tgδ bridge with built-in test voltage source are the most frequently used mobile test equipment. This paper presents a mobile HV resonant test set-up for installed cable testing and measuring instruments designed for on-site transformer insulation testing