Kerr electro-optic electric field measurement and electrical insulation performance in HVDC liquid dielectric systems

Abstract

A Kerr electro-optic electric field measurement technique was introduced for the direct measurement of electric field distributions and charging activities for a pressboard (PB) arrangement in oil/PB composite insulation systems, under HVDC and DC polarity reversal conditions. Next, under different PB arrangements in oil, the time dependent behavior of electric field stress was measured under both DC voltage and DC polarity reversal (DC-PR) conditions. The physical mechanisms of the movement and accumulation of charge carriers in the insulation systems were also clarified. Moreover, the breakdown discharge initiation by accumulated charges on PB was investigated and analyzed. FEM based electric field analysis techniques were also applied for liquid dielectric insulation systems, especially for the DC converter transformer structure. Finally, the electrical insulation performance for HVDC applications was discussed.