Resin based reactive compounds used for electrical insulation — Part 2: Methods of test
1Key Takeaways
IEC 60455-2:2023 RLV contains both the official IEC International Standard and its Redline version. The Redline version is available in English only and provides you with a quick and easy way to compare all the changes between the official IEC Standard and its previous edition. IEC 60455-2:2023 specifies methods of te…
2Expert Interpretation
An in-depth interpretation of the international standard IEC 60455-2:2023, Test methods for reactive resin compounds for electrical insulation, covering a full range of test methods for reactive compounds and their components, physical and chemical properties of cured compounds, electrical properties, thermal properties, etc., providing standardized technical support for the quality control of electrical insulation materials.
Standard Overview and Technical Background
IEC 60455-2:2023, "Reactive resin-based compounds for electrical insulation — Part 2: Test methods," is the fourth edition of the standard published by the International Electrotechnical Commission (IEC), replacing the third edition published in 2015. This standard, part of the IEC 60455 series of standards, specifically addresses solvent-free resin-based reactive compounds and their components for electrical insulation. It consists of three parts: Part 1: Definitions and general requirements; Part 2: Test methods; and Part 3: Specifications for individual materials.
This edition of the standard undergoes significant technical revisions. Major technical changes include the introduction of test methods related to IEC 60455-3-8 and the supplementation and updating of resin test methods. These changes reflect the latest developments in electrical insulation material technology, particularly the refinement of test requirements for resins used in cable accessories.
Analysis of the Standard Structure Framework
The IEC 60455-2 standard adopts a systematic structural design, classifies test methods according to material status and application characteristics, and establishes a complete test system framework.
| Test category | Number of test items | Main test parameters | Applicable material type |
|---|---|---|---|
| Reactive compounds and their components | 28 items | Flash point, viscosity, storage stability, curing characteristics, etc. | Unsaturated polyester, epoxy resin, phenolic resin, etc. |
| Curing reactive compounds | 23 items | Mechanical properties, thermal properties, electrical properties, chemical properties | All cured resin-based compounds |
| Special test methods | 5 items | Water-curing, thick-layer curing, and degree of cure determination are available. | Resin compounds for specific application scenarios |
Detailed Test Methods for Reactive Compounds and Their Components
Basic Physical Property Tests
Chapter 5 of the standard specifies 28 test methods for reactive compounds and their components, covering comprehensive quality control from raw materials to processing.
Processing performance tests include viscosity measurement (5.3), isothermal viscosity increase (processing time, 5.6), storage life (5.7), pot life (5.22), and gel time (5.23). These parameters directly impact the processability of the resin compound and the quality of the final product. In particular, the isothermal viscosity increase test accurately assesses the material's processing window at a specific temperature, providing a basis for temperature control during production. Thermal performance tests include flash point (5.1), softening temperature (5.9), and exothermic temperature rise (5.24). Flash point testing utilizes the closed cup equilibrium method (ISO 1523) and the Cleveland open cup method (ISO 2592) to ensure operational safety. Exothermic temperature rise testing has specialized testing procedures tailored to different resin types, with particularly stringent testing requirements for resin compounds used in cable accessories.
Chemical Composition Analysis
The standard specifies detailed chemical composition analysis methods, including:
- Volatile Organic Component Content (5.5): Evaluates environmental friendliness and safety of use
- Chlorine Content Analysis (5.12): Includes total chlorine content, inorganic chlorine content, and easily saponifiable chlorine content, which has an important impact on electrical properties
- Epoxy Equivalent Weight (5.14): A key quality indicator of epoxy resin
- Isocyanate Content (5.15): An important parameter of polyurethane system
- Hydroxy Value (5.17) and Acid Value (5.18): Important indicators of reactivity
Technical Analysis of Curing Compound Test Methods
Mechanical Properties Test System
Section 6.4 of the standard establishes a complete mechanical properties test system, using internationally accepted test standards to ensure the comparability of the results:
| Performance parameters | Test standards | Main test indicators | Application significance |
|---|---|---|---|
| Tensile properties | ISO 527 | Tensile strength, elongation at break, elastic modulus | Evaluate material tensile strength and toughness |
| Compression properties | ISO 604 | Compression strength, compression modulus | Evaluate pressure bearing capacity and dimensional stability |
| Flexural properties | ISO 178 | Flexural Strength, Flexural Modulus | Evaluate flexural strength and rigidity |
| Impact Strength | ISO 179-1/2 | Charpy Impact Strength | Evaluate impact resistance and toughness |
| Hardness | ISO 2039-1, ISO 868 | Ball Indentation Hardness, Shore Hardness | Evaluate surface hardness and wear resistance |
Thermal Performance Testing Technology
Thermal performance testing is a key step in the evaluation of electrical insulation materials. Section 6.5 of the standard specifies comprehensive thermal performance test methods:
Glass transition temperature (6.5.4) is measured using differential scanning calorimetry (DSC, ISO 11357-2) and thermomechanical analysis (TMA, ISO 11359-2). This parameter is crucial for determining the upper temperature limit of a material's operating temperature.
Temperature index (6.5.10) is measured in accordance with the IEC 60216 series of standards. This thermal aging test evaluates the long-term thermal stability of a material, providing a basis for the design life of electrical equipment.
Flame retardancy testing (6.5.5) uses the 50W horizontal and vertical flame test methods specified in IEC 60695-11-10 to evaluate the material's fire safety performance.
Electrical performance test requirements
As the core performance of electrical insulation materials, Section 6.7 of the standard specifies the electrical performance test methods in detail:
- Volume resistivity (6.7.1): Evaluates the basic insulation performance of the insulation material, with particular attention to performance changes after water immersion
- Dielectric loss factor and Relative permittivity (6.7.2): Measured in accordance with IEC 60250, evaluates the performance of the material under high-frequency electric fields
- Breakdown voltage and Electrical strength (6.7.3): Evaluates the voltage withstand capability of the material using IEC 60243-1
- Tracking index (6.7.4): Measured in accordance with IEC 60112:2020, evaluates the performance of the material in a humid and polluted environment
- Electrolytic Corrosion (6.7.5): Evaluates the corrosion potential of materials to metal components in accordance with IEC 60426.
Innovation and Application of Special Test Methods
Aqueous Cure Testing Technology
The aqueous cure test, specified in Section 5.26 of the standard, is a specialized test designed to address the effects of moisture that may be encountered in actual application environments. This test simulates the curing process of resin in a humid environment and, using a dedicated casting apparatus and testing procedures, evaluates the effects of moisture on the curing process and final performance.
The test apparatus includes a constant-temperature water area, a casting mold, and an inspection grid. After curing, the specimens are visually inspected for surface condition, internal condition, and voids, and a rating is assigned according to four tables in the standard. This test is crucial for quality control of insulation materials used in outdoor electrical equipment and humid environments.
Thick Layer Cure and Curing Process Emissions Testing
The Thick Layer Cure Test specified in Section 5.28 focuses on heat buildup and volatile emissions during the curing of large volumes of resin. Using a mold of specific dimensions, the test observes temperature changes and gas emissions during the curing process under controlled conditions.
This test provides valuable guidance for the insulation casting process of large electrical equipment, helping to optimize curing process parameters and avoid performance defects and safety issues caused by heat buildup.
Recommendations for the implementation of the standard and key points for quality control
Standardization of test sample preparation
Chapter 4 and Section 6.2 of the standard put forward clear requirements for the preparation and conditioning of test samples:
- Preparation and conditioning (4.1): Sample conditioning shall be carried out in accordance with ISO 291 standard atmosphere to ensure the consistency of the test environment
- Test sequence (4.2): A reasonable test sequence shall be specified to avoid the influence of previous tests on subsequent test results
- Test report (4.3): The necessary information that the test report should contain shall be clarified to ensure the traceability of the test results
Calibration and verification of instruments and equipment
Test instruments mentioned many times in the standard, such as rotational viscometer, Karl Fischer moisture meter, Health and Safety Precautions
Informative Annex A specifically discusses health and safety issues, reminding users to pay attention to the following when conducting tests:
- Potential skin irritation and allergic reactions of resin components
- Inhalation risk of volatile components
- Exothermic reactions and gas emissions during curing
- Appropriate personal protective equipment and ventilation requirements for the operating environment
Technology Development Trends and Standard Outlook
IEC 60455-2:2023 reflects the latest developments in the technology of resin-based compounds for electrical insulation, particularly the increasingly stringent requirements for environmental protection, safety, and reliability. The future development of the standard may focus on the following directions:
- Environmentally friendly materials: Requirements for the content of volatile organic components and restrictions on hazardous substances will be more stringent
- High performance: Test methods for special application environments such as high temperature and high frequency will continue to be improved
- Intelligent testing: The application of digital and automated testing technologies will improve test efficiency and accuracy
- Life prediction: Life prediction methods based on accelerated aging tests will be more accurate
The implementation of this standard will provide unified technical specifications for electrical equipment manufacturers, material suppliers and testing agencies, promote product quality improvement and technological innovation, and provide important guarantees for the safe and reliable operation of power systems.