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IS 3513:2000 (Part 1) is the Indian Standard (BIS) for resin-treated compressed wood laminates (compregs) - specification, part 1: for electrical purposes. This standard prescribes the requirements and methods of test for resin-treated compressed wood laminates (compregs) intended specifically for use as electrical insulation. It covers critical physical, mechanical, and dielectric properties required for reliable performance in electrical equipment such as transformers and switchgears.
Resin-treated compressed wood laminates (compregs) - Specification, Part 1: For electrical purposes
Overview
Status
Current
Usage level
Specialized
Domain
Materials Science — Wood and Other Lignocellulosic Products
! Ensure compregs are stored in a dry, well-ventilated environment, as moisture absorption severely degrades their dielectric strength.
! Because of the high density and synthetic resin impregnation, machining these laminates requires carbide-tipped or diamond-tipped tools to prevent rapid tool wear.
! Prior to use in high-voltage applications, vacuum drying and oil-impregnation are often recommended to maximize insulation resistance.
Specification for non-impregnated densified laminated wood for electrical purposes - Part 3-1: Specifications for individual materials - Sheets
Provides specific property requirements for sheet-form densified wood, directly comparable to IS 3513's grades.
EN 61061-1:2004European Committee for Electrotechnical Standardization (CENELEC), Europe
HighCurrent
Specification for non-impregnated densified laminated wood for electrical purposes - Part 1: Definitions, designation and general requirements
The European regional adoption of the IEC 61061-1 standard, making it the equivalent for the European market.
Key Differences
≠IS 3513 uses a simple three-grade system (CEW 1, CEW 2, CEW 3), whereas the IEC 61061 series uses a more detailed designation based on wood type (e.g., Beech 'B', Hornbeam 'F') and property profiles.
≠The minimum flexural strength required by IEC 61061-3-1 for its comparable types (e.g., ≥250 MPa) is significantly higher than that for the highest IS grade, CEW 1 (≥175 MPa).
≠IS 3513 specifies a more stringent requirement for insulation resistance after water immersion (≥ 1 x 10³ MΩ) compared to the IEC standard (≥ 1 x 10² MΩ for similar types).
Key Similarities
≈Both standards define materials made from wood veneers (typically beech) bonded under high pressure and heat with thermosetting phenolic resins, intended for electrical insulation.
≈The requirements for electric strength perpendicular to laminations when tested in hot oil (90 °C) are virtually identical, with both standards specifying values around 4.0 kV/mm for a 3mm thickness.
≈Both standards specify similar testing regimes and property requirements for dimensional stability, including comparable limits for water absorption and oil absorption.
≈The primary application specified in both standards is for manufacturing insulating components in oil-filled electrical equipment like transformers, such as clamping rings, spacers, and lead supports.
Parameter Comparison
Parameter
IS Value
International
Source
Density
1.25 to 1.35 g/cm³
1.30 to 1.40 g/cm³ (for Type DW-B)
IEC 61061-1:2004
Flexural Strength (Flatwise, highest grade)
≥ 175 MPa (Grade CEW 1)
≥ 250 MPa (Type DW-B 203.1)
IEC 61061-3-1:2006
Compressive Strength (Perpendicular to laminations)
≥ 250 MPa (Grade CEW 1)
≥ 250 MPa (Type DW-B 203.1)
IEC 61061-3-1:2006
Electric Strength (Perpendicular, 3mm thick, in oil @ 90°C)
≥ 4.0 kV/mm (Grade CEW 1)
≥ 4.0 kV/mm (Type DW-B 203.1)
IEC 61061-3-1:2006
Insulation Resistance (after 24h water immersion)
≥ 1 x 10³ MΩ
≥ 1 x 10² MΩ (Type DW-B 203.1)
IEC 61061-3-1:2006
Water Absorption (3mm thick, 24h immersion)
≤ 30 mg for 25x25mm specimen (approx. 1.2% by mass)
≤ 1.5% by mass
IEC 61061-3-1:2006
⚠ Verify details from original standards before use
A compreg is a compressed wood laminate made by impregnating wood veneers with synthetic resin (like phenol-formaldehyde) and consolidating them under heat and high pressure.
What are the primary applications of Part 1 compregs?+
They are used for electrical insulation components, structural supports, and cleats in heavy electrical equipment like transformers and switchgears.
Why is moisture content strictly limited in this specification?+
High moisture content increases electrical conductivity, significantly reducing the dielectric strength and insulation resistance of the laminate.