Electrical and optical-emission parallel study of natural ester liquids stressed by impulse high voltage

Dielectric insulation liquids are employed in a diversity of high voltage equipment due to their unique properties. Especially, natural ester oils exhibit high bio-degrability, non-toxicity and fire resistant properties, just to refer a few, making them a promising alternate of mineral oil dielectrics. Hereby, an effort for better understanding of breakdown phenomena in natural ester oils is attempted. In-situ electrical and optical emission signals are recorded during oil stressing by impulse high voltage (standard switching waveform). Point-to-plane electrode configuration is used, with constructive features imposed by the IEC 60897 Standard for non-homogenous field production. Two gap distances are examined i.e. 1 cm and 2 cm. We specially focus on the pre-breakdown phenomena which are well distinguished from the optical emission signals in the wider gap separation.