Effects of Types and Amounts of Additive Polymers on Resistivity and Dielectric Strength of Pure Water

We have been studying to use pure water harmless to the environment as a liquid insulating material of electrical power equipment. However, since the resistivity of pure water is much lower than that of insulating oils, the power loss in pure water becomes greater than that in oils. In addition, pure water tends to melt surrounding matters thereby the resistivity and the dielectric strength of pure water become low. In our previous studies, we reported that by adding non-ionic polymer surfactant to pure water, we can suppress the decrease in resistivity and improve the dielectric strength of pure water. This paper presents a study of the effects of types and amounts of additive polymers on resistivity and negative lightning impulse breakdown voltage of pure water. As the result, it was found that the resistivity and the dielectric strength of pure water with some non-ionic polymer individually added become higher than that of additive-free pure water. Furthermore, it was also suggested that the appropriate additive amount and the appropriate molecular weight of non-ionic polymer to pure water were in the ranges of 1 to 58 ppm and 2,000 to 1,000,000, respectively.