Diagnosis for oil-immersed insulation using partial discharge due to bubbles in oil

This paper deals with the partial discharge (PD) phenomenon and its use in the detection of small bubbles in oil and application to insulation diagnosis for oil-immersed power transformers. Bubbles in the oil strongly affect the reliability of insulation of oil-immersed power transformers as well as foreign particles. As the first step of the diagnosis of discharges in oil-immersed transformers, we conducted experiments to study the PD phenomena by measuring the PD characteristics and by observing the behavior of bubbles in oil. The experimental results, show that the /spl Phi/-q patterns strongly depends on the size of bubble.