Technical progress since 1969 revision of this standard has resulted in general agreement that a number of service stresses or factors, influence the life of electrical insulation, in materials tests and in systems used in electric equipment. While earlier editions of this standard made note of this fact, no guidance was provided to equipment committees who found a need to incorporate these additional factors into specific test guides.

These principles are intended to serve as a guide in the preparation of IEEE and other standards that deal with the selection of temperature limits and the measurement of temperature for specific types of electric equipment. They include an outline of the fundamental considerations and a review of the elements to be considered in applying the principles to specific cases. Guiding principles are included for the development of test procedures for 1) Thermal evaluation of electrical insulating materials; 2) Thermal evaluation of insulation systems; 3) Thermal classification of insulation systems for use in rating electric equipment. For many types of equipment proper evaluation of their electrical insulation for service conditions requires controlled exposure to a range of aging stresses which may or may not include thermal aging. The aging factors of influence may include thermal, electric, ambient (environmental), and mechanical stresses. Thermal aging has been widely used as a single ...