IEC 60667-2:2020

Overview

IEC 60667-2:2020 is an international standard developed by the International Electrotechnical Commission (IEC) that specifies the methods of test for vulcanized fibre sheets used in electrical applications. This document is the second part of a series addressing vulcanized fibre for electrical purposes, focusing on standardized testing procedures to ensure consistent and reliable assessment of material properties. The standard emphasizes that materials conforming to IEC 60667-2 meet established performance criteria, but actual material selection depends on application-specific requirements.

This 2020 edition supersedes the original 1982 release, introducing key technical revisions such as updated test methods for thickness, density, flexibility, internal ply adhesion, and arc resistance. It excludes composite materials made by laminating vulcanized fibres with adhesives.

Key Features include:

• Standardized conditioning and drying procedures for test specimens
• Measurement methods for thickness and density
• Mechanical and electrical property evaluations, including tensile strength, flexural strength, and electric strength
• Tests for water absorption, moisture content, shrinkage, internal ply adhesion, and arc resistance

The standard plays a vital role in ensuring the safety, performance, and quality of vulcanized fibre when used as an insulating material in electrical devices and systems.

Key Topics

Conditioning and Drying of Test Specimens

• Conditioning: Specimens must be conditioned under controlled temperature and humidity (23 °C ± 2 K, 50% ± 5% RH) for specified time intervals based on thickness to ensure consistent moisture content.
• Drying: Drying is conducted in a ventilated oven at 105 °C ± 2 K, with drying times varying depending on material thickness.

Thickness and Density Measurement

• Thickness is measured using ten points along the specimen’s circumference per IEC 60641-2 methodology, reporting mean values.
• Apparent density tests use multiple samples, ensuring precise measurement of mass, length, width, and thickness.

Mechanical Properties Testing

• Tensile strength and elongation: Assessment of material's response to uniaxial stress.
• Flexural strength: Evaluated through bending tests to understand the resistance to deformation.
• Flexibility (bending): New bending methods added to assess material flexibility under practical conditions.

Electrical Properties Testing

• Electric strength up to 3 mm thickness: Assessment of breakdown voltage to ensure adequate insulation resistance.
• Arc resistance: A newly added test to measure resistance to high-voltage, low-current arc discharges, critical for electrical safety.

Additional Evaluations

• Water absorption and moisture content: Determined to predict material behavior in humid environments.
• Internal ply adhesion: Verification of the bond strength between plies, vital for mechanical integrity.
• Shrinkage: A critical dimension stability parameter included to assess long-term reliability.

Applications

IEC 60667-2:2020 is primarily targeted at manufacturers, testing laboratories, and quality assurance professionals involved with vulcanized fibre sheets for electrical insulation purposes. Typical applications include:

• Electrical and electronic insulation components such as washers, spacers, and insulating sheets.
• Components in transformers, switchgear, and circuit breakers where reliable dielectric and mechanical properties are mandatory.
• Use in manufacturing electrical devices operating under various environmental and mechanical stresses necessitating standardized testing.
• Assisting engineers and designers in the selection and qualification of vulcanized fibre materials meeting precise specifications for durability and safety.

By following IEC 60667-2’s methodologies, companies ensure conformity with internationally recognized standards, thereby enhancing product reliability and global market acceptance.

Related Standards

IEC 60667-2 is part of the broader IEC 60667 series focused on vulcanized fibre materials:

• IEC 60667-1: Definitions and general requirements for vulcanized fibre for electrical purposes.
• IEC 60667-3: Specifications for individual vulcanized fibre materials, detailing performance criteria for different grades.

Additional normative references integral to testing methods include:

• IEC 60641-2: Methods for testing pressboard and presspaper used in electrical insulations.
• IEC 61621: Resistance tests to high-voltage, low-current arc discharges for dry solid insulating materials.
• ISO 178: Plastics determination of flexural properties.
• ISO 287: Determination of moisture content in paper and board materials.

These standards complement IEC 60667-2 by providing frameworks for material characterization and ensuring consistent electrical performance, which are essential in the electrotechnical industry.

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Keywords: IEC 60667-2, vulcanized fibre, electrical insulation, methods of test, arc resistance, tensile strength, flexural strength, moisture content, internal ply adhesion, electrical insulating materials, IEC standards, electrical safety testing.