IEC 60216-5:2022

Overview

IEC 60216-5:2022 - "Electrical insulating materials - Thermal endurance properties - Part 5: Determination of relative temperature index (RTI) of an insulating material" specifies the experimental and calculation procedures for deriving the Relative Temperature Index (RTI) of electrical insulating materials. It is part of the IEC 60216 series and is intended to be read together with IEC 60216‑1, IEC 60216‑2 and IEC 60216‑3. This edition updates Annex C (computer program) and clarifies terminology (ATE/RTE → ATI/RTI).

Key topics and technical requirements

• Purpose: Defines how to calculate the RTI from thermal‑ageing experimental data obtained under the protocols of IEC 60216‑1 and IEC 60216‑2.
• Experimental procedures:
  • Selection of a reference electrical insulating material (EIM).
  • Selection of appropriate diagnostic tests to assess extent of ageing (destructive, non‑destructive or proof tests).
  • Ageing procedures including guidance for short‑term thermal ageing.
• Calculation procedures:
  • Calculation of intermediate thermal endurance parameters and derivation of RTI values.
  • Statistical and numerical tests (precision of correlation time, lower confidence interval of RTI, and extrapolation checks).
  • Guidance for assessment after a single fixed time and temperature without extrapolation.
• Results and reporting:
  • Required results, statistical tests, and recommended report contents for reproducible RTI reporting.
• Annexes:
  • Informative material on repeatability, thermal class assignment, selection of reference EIM and a reworked Annex C providing a computer program framework for the RTI calculations.

Practical applications and who uses it

IEC 60216‑5:2022 is used by professionals who need to evaluate or document the thermal endurance of insulating materials and assign thermal classes:

• Material manufacturers - to characterize and compare thermal endurance and declare RTI for product datasheets.
• Testing laboratories and QA teams - to perform standardized ageing tests, compute RTI, run statistical checks and issue compliant test reports.
• Design and R&D engineers - to select insulation materials and estimate thermal performance and longevity under elevated temperatures.
• Certification bodies and standards engineers - to verify compliance, support insulation classification and integrate RTI data into system-level thermal class assessments.

Related standards

• IEC 60216‑1:2013 - Ageing procedures and evaluation of test results
• IEC 60216‑2:2005 - Choice of test criteria
• IEC 60216‑3:2021 - Instructions for calculating thermal endurance characteristics

Keywords: IEC 60216-5:2022, RTI, relative temperature index, electrical insulating materials, thermal endurance properties, thermal class, ageing procedures, insulation testing.