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

Foreword

This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1: Structure and Drafting Rules of Standardization Documents". Drafting.

This document is Part 7 of GB/T 11026 "Heat Resistance of Electrical Insulation Materials". GB/T 11026 has already published the following parts.

---Part 1: Aging Procedures and Evaluation of Test Results;

---Part 2: Selection of Test Judgment Criteria;

---Part 3: Procedures for calculating heat resistance characteristic parameters;

---Part 4: Aging Oven - Single Chamber Oven;

---Part 5: Precision ovens with aging temperatures up to 300°C;

---Part 6: Aging Ovens - Multi-chamber Ovens;

---Part 7: Determining the Relative Temperature Index (RTI) of Insulating Materials;

---Part 8: Determining the heat resistance index (TI and RTI) of insulating materials using the fixed time limit method;

---Part 9: Guidelines for calculating heat resistance using simplified procedures;

---Part 10: Guidelines for accelerating the determination of the relative heat resistance index (RTEA) based on activation energy calculations using analytical testing methods.

This document replaces GB/T 11026.7-2014 "Heat Resistance of Electrical Insulation Materials - Part 7: Determination of Relative Heat Resistance of Insulation Materials".

Compared with GB/T 11026.7-2014, the main technical changes in the "Real-Time Expansion (RTE) Index" are as follows, except for structural adjustments and editorial changes.

a) The term "Relative Heat Resistance Index (RTE)" has been changed to "Relative Temperature Index (RTI)" (see full text, 2014 edition).

b) Added "When thermal stress is the primary aging factor, the calculation procedure in this document is applicable to determining the heat resistance, etc., of electrical insulation systems." Level (see Chapter 1);

c) The term "validation test" has been changed to "inspection test" (see Chapter 1, 2014 edition);

d) The term "estimated heat resistance index" has been changed to "estimated temperature index" (see 3.1.2, 2014 version 3.1.2);

e) The term "relevant time" has been changed to "relevant time of RTI" (see 3.1.6, 2014 version 3.1.6);

f) The term "relative heat resistance index" has been changed to "relative temperature index" (see 3.1.10, 2014 edition of 3.1.10).

This document is modified to adopt IEC 60216-5:2022 "Electrical insulating materials - Heat resistance - Part 5: Determination of relative temperature Index (RTI) of insulating materials".

The technical differences between this document and IEC 60216-5:2022, and the reasons therefor, are as follows.

a) IEC 60216-1:2013 (see 5.3) has been replaced with the normatively referenced GB/T 11026.1 to improve operability;

b) Modify "shall comply with the requirements of IEC 60216-1:2013, 5.3.2, 5.4 and 5.5" to "shall comply with GB/T 11026.1". The requirements (see 5.3) are to increase operability;

c) IEC 60216-2:2005 (see Chapter 1) has been replaced with the normatively referenced GB/T 11026.2 to increase operability.

The following editorial changes have been made to this document.

---In accordance with the GB/T 11026 series standard numbering, the original English name has been changed to "Electrical Insulation Materials Heat Resistance Part 7: Determination" "Relative Temperature Index (RTI) of Insulation Materials";

---Replace IEC 60216-3 and IEC 60216-6 in the non-software examples of Informative Appendix C with GB/T 11026.3 and GB/T 11026.3 respectively. GB/T 11026.8.

Introduction

GB/T 11026 aims to establish test procedures, test judgment criteria, aging ovens, and relative standards for the heat resistance of electrical insulation materials. Procedures for evaluating heat resistance index, etc.

GB/T 11026 consists of the following 10 parts.

---Part 1: Aging Procedures and Evaluation of Test Results. The aim is to establish aging procedures for evaluating the heat resistance of insulating materials and to improve... How to evaluate the results of aging tests.

---Part 2: Selection of Test Judgment Criteria. The purpose is to propose criteria for judging the endpoint of thermal aging tests on insulating materials.

---Part 3: Procedures for calculating heat resistance characteristic parameters. The purpose is to establish the method for obtaining heat resistance characteristic parameters using GB/T 11026.1 and GB/T 11026.2.

The experimental data were used to derive a calculation program for the heat resistance characteristic parameters.

---Part 4: Aging Oven - Single-chamber oven. The purpose is to specify that the temperature used for heat resistance aging tests should be 20°C higher than ambient temperature.

A single-chamber oven that operates over the entire or a portion of the temperature range of 500°C.

---Part 5: Precision ovens with aging temperatures up to 300°C. The purpose is to specify the temperature relative to ambient temperature used in heat resistance aging tests.

A precision oven that operates within the entire or part of the temperature range of 20°C to 500°C.

---Part 6: Aging Oven - Multi-chamber Oven. The purpose is to specify that the temperature used for heat resistance aging tests should be 20°C higher than ambient temperature.

A multi-chamber oven that operates within or in part of a temperature range of 500°C.

---Part 7: Determination of the Relative Temperature Index (RTI) of Insulation Materials. The aim is to establish the use of GB/T 11026.1 and... The test and calculation procedures for deriving the relative temperature index from the test data obtained in GB/T 11026.2.

---Part 8: Determining the Heat Resistance Index (TI and RTI) of Insulating Materials Using the Fixed Time Limit Method. The aim is to establish the use of fixed time limits... The experimental and calculation procedures for deriving the heat resistance index were developed.

---Part 9: Guidelines for Calculating Heat Resistance Using Simplified Procedures. The aim is to establish simplified procedures for obtaining the heat resistance properties of insulating materials.

---Part 10: Guidelines for accelerating the determination of the relative heat resistance index (RTEA) based on activation energy calculations using analytical experimental methods. Objective The goal is to establish a thermal degradation activation energy obtained through thermal analysis and a lifetime point obtained through conventional thermal aging tests, and to evaluate the insulation performance.

The procedure for determining the relative heat resistance index of insulating materials.

1 Scope

This document establishes the criteria for deriving the relative temperature index of materials from test data obtained according to GB/T 11026.1 and GB/T 11026.2.

The test and calculation procedures are as follows. 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.

According to this, because all samples may have stopped at some point after the median time and before the endpoint time, therefore, from a non-destructive perspective... Data obtained from failure tests or inspection tests may be incomplete (see GB/T 11026.1).

This document provides guidance for the preliminary classification of the heat resistance level of insulating materials based on their thermal aging properties.

Although the heat resistance rating of electrical insulation materials is not directly related to the heat resistance rating of electrical insulation systems, the heat resistance of electrical insulation systems... The grading system follows the same concepts presented in this section. When thermal stress is the primary aging factor, the calculation procedures in this document are suitable for determining... Heat resistance rating of electrical insulation systems.

2 Normative references

The contents of the following documents, through normative references within the text, constitute essential provisions of this document. Dated citations are not included.

For references to documents, only the version corresponding to that date applies to this document; for undated references, the latest version (including all amendments) applies. This document.

GB/T 11026.1 Electrical insulating materials - Heat resistance - Part 1: Aging procedures and evaluation of test results (GB/T 11026.1-2016, IEC 60216-1:2013, IDT)

GB/T 11026.2 Electrical insulating materials - Heat resistance - Part 2: Selection of test criteria (GB/T 11026.2-2012, IEC 60216-2:2005, IDT)

GB/T 11026.3-2025 Electrical insulating materials - Heat resistance - Part 3: Procedure for calculating characteristic parameters of heat resistance (IEC 60216-3:2021, MOD)

Note: There are no technical differences between the content referenced in GB/T 11026.3-2025 and the content referenced in IEC 60216-3:2021.

3 Terms, Definitions and Symbols