Thermal Stability of Micaceous Insulation of High Voltage Machines

The steady state condition of heat flow is important to design engineers to establish norms for insulation systems in respect to operating voltage and consequent temperature rise to prevent thermal instability, causing run-away conditions. The temperature distribution equation has been solved and the results have been applied to three practical situations, e. g. (1) ideally cooled system of electrodes where both iron and copper are at the same temperature, (2) water cooled machines, and (3) air cooled machines. This analysis gives the voltage at which thermal run away occurs. Suggestions to improve the maximum voltage by decreasing the dependence of loss factor on temperature, improving thermal conductivity, and reducing electrical conductivity, have been given in the paper.