IEC 60641-2:2004

Overview

IEC 60641-2:2004 - "Pressboard and presspaper for electrical purposes - Part 2: Methods of tests" specifies standardized test methods for pressboard and presspaper used as electrical insulating materials. The standard applies to single-sheet pressboard and presspaper (not laminated materials) and defines how to perform physical, chemical and electrical tests to verify conformance with the material specifications given in IEC 60641-3. Where ISO methods are referenced, IEC 60641-2 provides identification only; the full ISO text must be used for procedural details.

Key topics and requirements

The standard defines test procedures and reporting rules for a comprehensive set of properties, including:

• Dimensional and physical tests

  • Thickness (gauge-setting, procedure, tolerances)
  • Apparent (bulk) density
  • Moisture content (oven-drying methods referenced to ISO 287)
  • Shrinkage and compressibility (revised methods)

• Mechanical properties

  • Tensile strength and elongation (non-folded and folded specimens)
  • Internal tearing resistance and edge tearing resistance (Elmendorf and related techniques)
  • Plybond/cohesion between plies (rewritten method)

• Chemical and contamination tests

  • Ash content (ISO 2144)
  • Conductivity and pH of aqueous extracts (conductivity method rewritten)
  • Oil absorption
  • Presence of metallic particles - new X‑ray detection method introduced (also chemical methods described)

• Electrical tests

  • Electric strength (test voltages, specimen preparation, tests in air and oil in accordance with IEC 60243-1)
  • Conducting path assessments and related acceptance criteria

• Editorial changes vs previous edition

  • Cancelled tests: flexibility, conductivity of organic extract, contamination of liquid dielectrics
  • Rewritten tests: compressibility, conductivity of aqueous extract, cohesion between plies
  • New test: metallic particles by X‑ray

Applications and who uses it

IEC 60641-2 is used by:

• Manufacturers of pressboard and presspaper for electrical insulation (quality control and product development)
• Independent testing laboratories and certification bodies (type testing, batch verification)
• Transformer, switchgear and electrical equipment designers specifying insulation materials
• Procurement/specification engineers ensuring supplied materials meet IEC 60641 series requirements
• R&D and failure analysis teams assessing material ageing, contamination or particulate inclusion

Using these standardized test methods helps ensure consistent electrical performance, long-term reliability and safe operation of high-voltage equipment.

Related standards

• IEC 60641-1: Definition and general requirements
• IEC 60641-3: Specifications for individual materials (pressboard / presspaper sheets)
• IEC 60243-1: Electrical strength test methods
• IEC 60296: Transformer insulating oils
• ISO 287, ISO 534, ISO 1924-2, ISO 1974, ISO 2144 (referenced test-method standards)

Keywords: IEC 60641-2, pressboard test methods, presspaper testing, electrical insulating materials, metallic particles X-ray, compressibility, electric strength testing.