GB/T 11026.7-2025 Electrical insulating materials—Thermal endurance properties—Part 7:Determination of relative temperature index(RTI)of an insulating material

Scope

This document establishes the test and calculation procedures required to derive the relative temperature index of materials based on test data obtained in accordance with GB/T 11026.1 and GB/T 11026.2. These calculation procedures supplement the calculation procedures in GB/T 11026.3. This document also provides guidelines for evaluating thermal aging at a single fixed time and temperature without extrapolation. In principle, test data can be obtained through destructive testing, non-destructive testing, and inspection testing. Destructive testing is typically used to obtain data, as all samples may have reached a point before the end time after passing the median time, and the test may have been stopped before this point. Therefore, the data obtained from non-destructive testing or inspection testing may be incomplete (see GB/T 11026.1). This document provides guidance for preliminary classification of the heat resistance of insulating materials based on their thermal aging performance. Although the heat resistance rating of electrical insulating materials is not directly related to the heat resistance rating of electrical insulation systems, the heat resistance rating classification of electrical insulation systems follows the same concept proposed in this section. When thermal stress is the main aging factor, the calculation procedures in this document are applicable to determining the heat resistance rating of electrical insulation systems.

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