Influence of water content on breakdown behavior of transformer oil

This paper deals with investigations on the influence of solved water on the breakdown behavior of transformer oils. Experiments were carried out using weakly inhomogeneous fields in a rod-plane geometry with gap distance 60 mm and lightning impulse voltage. Both optical and statistical investigation were made in order to shed light on the effect. Water content varied from 10 to 85 ppm respectively. Unlike expected from measurements with AC-voltage, results showed that the impulse withstand voltages decreases first and reincreases with increasing water content. The effect of water on streamer shape and propagation velocity will be discussed in detail.