scope:

Guiding principles are included for the development of test procedures for -- Thermal evaluation of electrical insulating materials (EIM) -- Thermal evaluation of electrical insulation systems (EIS) -- Thermal classification(Footnote 1) of EIS for rating electric equipment The principles are presented in the following order: -- Clause 4, General concepts -- Clause 6, Evaluation of the thermal capability of EIM -- Clause 7, Limiting temperatures and their measurement for EIS -- Clause 8, Thermal evaluation of EIS In the application of these principles, variations are necessary to suit the widely different types of equipment and service conditions that are considered in equipment standards. When specific equipment, IEEE, or other recognized standards based on these principles are available, they should take precedence over this recommended practice. Footnote 1 - Historically, the term thermal classification has been used in reference to both insulation systems and to electric equipment. Therefore, for clarity, thermal classification should always be used in combination with the word system or equipment, for example, Class 155 System.

Purpose

This recommended practice is intended to serve in the preparation of standards that are principally concerned with the thermal endurance of EIM and simple combinations thereof, with the establishment of limiting temperatures of EIS, and with the provision of general principles for thermal classification of EIS.