HVDC transformer insulation: oil conductivity

JWG A2/D1.41 (HVDC transformer insulation: Oil conductivity) reviewed techniques and standards and developed recommendations for conductivity measurements for oil and for oil-impregnated pressboard that are both simple and representative for the conditions in a HVDC insulation system and that exhibit reduced spread. Oil-conductivity values of HVDC transformers at production and in service were determined and the impact of the values found in respect of dielectric test effectiveness and reliability was analysed.