scope:

This test procedure is intended to give a direct evaluation of the thermal aging characteristics of the composite insulation system of a liquid-immersed distribution or power transformer. The evolution of bubbles or their effect on dielectric strength is not considered. It is to be noted that the liquid in which the transformer is immersed is to be considered a part of the insulation system.

It is the intent of the procedure to provide that each component of the insulation structure operate during the test under conditions that are, as nearly as possible, the same as those that it would encounter in service. Thus, it is intended that each component be evaluated in accordance with its actual function.