The Effect of Heat on Paper Insulation

A discussion is given in detail of the mechanical properties of paper especially as influenced by drying, heating, and impregnating. Tests for measuring the changes due to these causes are discussed and it is shown that tensile tests are unsatisfactory for this purpose. A measurement of tearing resistance is found to be satisfactory and two machines for this purpose are described. Measurements are given of rate of deterioration of paper at different temperatures. The relation of these data to allowable operating temperature is considered. No discussion is given of the various causes including heating due to dielectric losses which affect the limiting temperature of high-voltage, cables. The rapid increase of deterioration with temperature is shown. Emphasis is placed on the importance of not exceeding intended temperatures through lack of knowledge of conditions.