The dielectric properties of paper

This paper is an outline of a detailed investigation of the fundamental dielectric propeities of paper. Measurements were made under carefully controlled conditions covering a very wide range, on three representative kinds of paper, both in the dry condition, and after impregnation with oil. The currents flowing through the material under various conditions were found to be affected in widely different ways by changes of moisture content, temperature, and voltage. The laws governing the various changes lead to the following conclusions. Power-loss phenomena under ordinary conditions are manifestations of dielectric absorption obeying Hopkinson´s laws. The part played by normal conduction (leakage) in power-loss phenomena is usually negligible, but it is likely to be the determining factor in the breakdown of paper at high voltages. Impregnation with transformer oil merely serves to exclude moisture: it does not appreciably affect thebasic properties of the paper.