Testing equipment: Variations and their effect on the apparent dielectric strength of insulating fluids

Some time ago a survey of the electric power companies showed that the dielectric strength measurement was the one test most relied upon to determine whether insulating oils were satisfactory for initial service and for continued service in both oil cooled electric equipment and electric switch gear. Its popularity as a service test is probably due in part to being simple to perform and in part to the fact that a number of contaminants which adversely effect service operations tend to lower the dielectric strength of insulating fluids.