is the ratio of the power in watts (W) dissipated in an insulating medium to the product of the effective values of voltage (V) and current (I) in volt-amperes; a measure of the tendency of an electrical insulating oil, which is a dielectric (nonconductor of electricity), to permit leakage of current through the oil, as determined by test method ASTM-D-924. Such current leakage is called dielectric loss. The lower the power factor, the lower the dielectric loss. Determination of power factor can be used to indicate not only the inherent dielectric properties of an oil, but the extent of deterioration of a used oil, since oxidation products and other polar contaminants reduce dielectric strength, causing the power factor to rise. Power factor is related to dissipation factor.