Insulating paper

In a paper concerning important properties of electrical insulating papers by H. H. Race, R. J. Hemphill and H. S. Ehdicott (1) information concerning the types of papers commonly used in electrical apparatus and typical data concerning some of their physical and chemical properties are presented along with a description of test methods used to evaluate and control these properties. It is pointed out that the desired electrical properties are directly dependent upon the physical and chemical properties incorporated into the paper by the maker. Power factor is said to be one of the most important characteristics of capacitor paper and methods of measurement and calculation of the power factor of impregnated paper are described. The conclusion is reached that the dielectric loss in impregnated paper depends upon the dielectric loss in the paper and on the relative dielectric constants of impregnant and paper but ordinarily not on the power factor of the liquid impregnant. In these calculations the assumption that the paper and the impregnant act in series most nearly fits the experimental results, there are, however, little understood effects resulting from adsorption of polar molecules by the cellulose which are difficult to calculate.