This International Standard now distinguishes between thermal classes for electrical insulation systems and electrical insulating materials. It establishes the criteria for evaluating the thermal endurance of either electrical insulating materials (EIM) or electrical insulation systems (EIS). It also establishes the procedure for assigning thermal classes.
The standard is applicable where the thermal factor is the dominant ageing factor.
Note A thermal class is not assigned to an EIM as related to its use in an EIS