抄録
In this paper the effect of water on the high field conduction and breakdown in insulating oils is discussed from a viewpoint of the state of water. The FT near infrared spectrometry is used to analyze the state of water. By means of decomposing the observed NIR spectra, it is found that there are three different states in the water dissolved in dioctyl-phthalate (DOP), namely free water, cluster water and hydrogen bonded water.
When the water content is lower than 200ppm, most of dissolved water consists of the hydrogen bonded water. In this region a rapid rise of conduction current does not occur. On the other hand when the water content is higher than 200ppm, dissolved water consists of the cluster water. The conduction current, therefore, increases by the dissociation of the cluster water by the effect of applied field.
From this study it is found that the cluster water acts as the source of the free water, and the breakdown strength depends on the amount of the free water. Furthermore the hydrogen bonded water has little effect on the high field conduction and breakdown in insulating oils.
