The effect of absorbed water on electrical treeing in epoxy resins

The electrical tree growth behaviour in CY1300 and CT1200, the base resins used in switchgear and transformer bushings, have been examined after conditioning the samples over a range of temperature and relative humidity environments. The time to breakdown for both CY1300 and CT1200 samples stored in the laboratory or in water at 20/spl deg/C show the classic U-shaped dependence with sample age or moisture uptake. The anomalous diffusion model was found to be a good description of the experimental data over a wide range of temperatures and different relative humidity environments.