Breakdown behaviour of new insulation liquids under AC and DC stress and gap distances over 10 mm

Insulation liquids are well known and therefore used in many high voltage applications. Due to their high breakdown voltages, breakdown tests are usually done with gap distances of 2,5 mm according to IEC standards to allow compact test arrangements. However, in high voltage equipment oil insulated gaps can reach multiple centimetres. But because of the volume effect, the breakdown voltage does not increase linear with the gap distance. Additionally for newer insulation liquids and for the more and more important high voltage DC applications, less experience exists, because tests are usually done at frequencies of 50 or 60 Hz. In this experimental study a test vessel is constructed to allow breakdown test at longer gap distances and with voltages of up to 300 kV AC and 400 kV DC. The test…