Transformer Pressboard Introduction

Transformer Insulating Pressboard is a critical insulating material used inside power transformers. It is manufactured from wood fibers (e.g., sulfate wood pulp) through high-temperature, high-pressure molding and chemical treatment, offering excellent electrical insulation and mechanical strength. Its primary functions include:

Electrical Insulation: Isolating windings and cores at different voltage levels.

Structural Support: Securing winding positions and withstanding electromagnetic and mechanical stresses.

Thermal Management: Collaborating with transformer oil to form heat dissipation channels.

Applications: Widely used in oil-immersed transformers for interlayer winding insulation, lead support, insulating cylinders, spacers, and other components.

Key Properties

High Dielectric Strength：Typical value: 10–25 kV/mm (dependent on thickness and density), ensuring reliability in high-voltage environments.

Superior Mechanical Performance：

Tensile strength: Longitudinal ≥80 MPa, transverse ≥40 MPa (higher after densification).

Compressive strength: Densified pressboard exceeds 200 MPa, suitable for load-bearing structures.

Thermal Resistance：

Thermal class: Class A (105°C); modified variants may reach Class E (120°C).

Long-term operating temperature: 90–100°C (in oil-immersed conditions).

Oil Absorption and Impregnation：

Oil absorption rate: 20–30%, synergizing with transformer oil to enhance insulation.

Environmental Compatibility：

Biodegradable; some products comply with RoHS standards.

Process Adaptability：

Can be punched, laminated, or bent; supports customized designs.

Key Technical Parameters

4. Selection Guidelines

1.Voltage Level Compatibility

Low-voltage transformers (<35kV): Use standard pressboard (1–3mm thickness, dielectric strength ≥15kV/mm).

High-voltage transformers (≥110kV): Opt for high-density pressboard (1.2–1.3g/cm³, 3–8mm thickness, dielectric strength ≥20kV/mm); laminated structures may be required.

2.Mechanical Requirements

Spacers/Support Strips: Prioritize densified pressboard with high compressive strength (≥150MPa).

Insulating Cylinders/End Rings: Balance tensile strength (longitudinal ≥100MPa) and flexibility.

3.Thermal Class Suitability

Standard oil-immersed transformers: Class A (105°C) suffices.

High-temperature applications (e.g., tropical regions): Use modified pressboard (Class E, 120°C) or heat-resistant coatings.

4.Environmental Adaptability

High-humidity environments: Select low-hygroscopicity pressboard (moisture ≤3%) or pre-dried variants.

Eco-friendly requirements: Choose halogen-free, recyclable pressboard (compliant with IEC 61249).

5.Process Compatibility

Automated winding equipment: Requires low shrinkage (≤0.3%) and high dimensional stability.

Oil impregnation: Use high-porosity pressboard (oil absorption ≥25%) for faster impregnation.

6.Supplier Qualifications

Certifications: ISO 9001, IEC 60641, UL certification.

Customization: Support for laser-cut custom shapes.

7.Cost Optimization

Standard models: Use common thicknesses (e.g., 1.5/3.0/6.0mm) to reduce costs.

Hybrid designs: Combine high-grade pressboard  with standard grades elsewhere.

Case Studies

500kV EHV Transformer: Utilizes 6mm thick laminated high-density pressboard (density 1.25g/cm³, dielectric strength 22kV/mm), with epoxy-resin-reinforced pressboard for end insulation.

Offshore Wind Power Transformer: Employs modified pressboard with low moisture (≤3%) and salt spray-resistant treatment.

Precautions

Storage: Temperature 20–30°C, humidity <50%, elevated on pallets to avoid ground contact.

Pre-processing: Vacuum drying at 110°C for 24 hours to remove residual moisture.

Failure Modes: Monitor partial discharge and carbonization via regular oil chromatography.

By systematically evaluating voltage, mechanical, environmental, and cost factors, precise selection ensures long-term transformer reliability. Validate choices using design parameters and supplier documentation.