Transactions section: Reprint of corresponding pages from the current annual AIEE transactions volume

The causes of dielectric loss in insulating oils and the means to reduce it to a minimum have always been important in high voltage engineering. In this study the relationships between the amount of impurities, which furnish a source of free ions in an oil, and the viscosity, which influences the mobility of the ions, on the one hand and the dielectric loss on the other are investigated. The results present some definite relationships between them and point out that in two oils of the same “electrical purity,” the one with higher viscosity will have lower dielectric loss.