Products Description
Thermally Upgraded Insulation Pressboard (1.0mm) for Power Transformers
Thermally upgraded insulation pressboard is a high-density cellulose board whose thermal aging resistance has been chemically enhanced, making it a premium choice for the insulation system of oil-immersed power transformers. Unlike standard pressboard, the thermally upgraded grade is modified with nitrogen-containing compounds - a feature quantified by its nitrogen (N) content, which for Weshare's 1.0mm board is 1.78% within a required 1.5–3.0% band.
Produced and tested to enterprise standard Q/321202KXD022-2025, this 1.0mm pressboard combines high mechanical strength (tensile MD 113.43 MPa / CMD 65.71 MPa), high dielectric strength (43.69 kV/mm in oil), low ash (0.47%) and low shrinkage - the combination transformer designers rely on for long-life, heat-resistant insulation barriers, spacers and formed components.
What "Thermally Upgraded" Actually Means
"Thermally upgraded" is a controlled, measurable property - not a marketing label. It refers to cellulose that has been chemically stabilised to resist thermal degradation (ageing) at elevated winding hot-spot temperatures. The key indicators are:
Nitrogen (N) content 1.5–3.0% (tested 1.78%) - the nitrogen-containing modification is the actual thermal-upgrading agent.
Low ash 0.47% and low water-extract conductivity 3.61 mS/m - evidence of high chemical purity, which protects dielectric performance.
Neutral pH 7.34 (within 6.0–9.0) - indicates stability against acid generation that accelerates cellulose ageing.
Product Benefits
Thermal-life benefits
Chemically upgraded thermal stability - the N-containing modification (1.78%) slows cellulose thermal ageing, extending insulation service life.
Suited to elevated hot-spot temperatures - a better fit than standard pressboard for high-temperature-loading power transformers.
Stable against acid generation - neutral pH (7.34) reduces the self-accelerating ageing seen in inferior board.
Dielectric benefits
High electrical breakdown strength - 43.69 kV/mm in oil and 13.67 kV/mm in air, well above the 35 / 12 kV/mm limits.
High purity - low ash (0.47%) and low extract conductivity (3.61 mS/m) minimise conductive contaminants.
Excellent oil impregnation - high oil absorption (17.89%) supports void-free oil-paper insulation.
Mechanical & structural benefits
High tensile strength - 113.43 MPa (MD) / 65.71 MPa (CMD) for reliable mechanical support.
High density - 1.09 g/cm³ within the 1.05–1.25 range, for strength and dimensional integrity.
Good compressibility (8.05%) with high recovery (55.09%) - conforms under clamping and rebounds to hold the stack tight.
Low shrinkage - MD 0.30%, CMD 0.40%, thickness 3.01%, so dimensions stay stable through drying and service.
Strong ply adhesion - multi-ply rupture with a distinctly fibrous surface confirms a sound, delamination-resistant board.
Process & handling benefits
Low moisture content (4.0%) - shortens drying cycles and reduces energy in transformer processing.
Machinable and formable - suitable for cutting, punching, milling and forming into shaped components.
Consistent, verified quality - every batch released against a full routine test report.
Technical Specifications
| Test item | Unit | Standard (limit) | Result | Verdict |
|---|---|---|---|---|
| Thickness deviation | % | ± 7.5 | −1.0 | Pass |
| Density | g/cm³ | 1.05 – 1.25 | 1.09 | Pass |
| Tensile strength - MD | MPa | ≥ 90 | 113.43 | Pass |
| Tensile strength - CMD | MPa | ≥ 60 | 65.71 | Pass |
| Elongation - MD | % | ≥ 3.5 | 5.54 | Pass |
| Elongation - CMD | % | ≥ 4.0 | 5.14 | Pass |
| Compressibility (C.S.) | % | ≤ 11 | 8.05 | Pass |
| Recoverable part (Crev) | % | ≥ 45 | 55.09 | Pass |
| Shrinkage - MD | % | ≤ 0.7 | 0.30 | Pass |
| Shrinkage - CMD | % | ≤ 1.0 | 0.40 | Pass |
| Shrinkage - thickness | % | ≤ 6.0 | 3.01 | Pass |
| Moisture content | % | ≤ 8.0 | 4.0 | Pass |
| Ash content | % | ≤ 0.5 | 0.47 | Pass |
| Conductivity of aqueous extract | mS/m | ≤ 6.0 | 3.61 | Pass |
| pH of aqueous extract | - | 6.0 – 9.0 | 7.34 | Pass |
| Nitrogen (N) content | % | 1.5 – 3.0 | 1.78 | Pass |
| Oil absorption | % | ≥ 12 | 17.89 | Pass |
| Electrical breakdown strength - in air | kV/mm | ≥ 12 | 13.67 | Pass |
| Electrical breakdown strength - in oil | kV/mm | ≥ 35 | 43.69 | Pass |
| Ply adhesion | - | Tear of one or more plies, distinctly hairy / ragged surface (visual) | Multi-ply rupture, distinctly hairy / ragged surface | Pass |
Application scenarios
Thermally upgraded insulation pressboard is used throughout the insulation system of oil-immersed power and distribution transformers:
Barriers and partitions between windings and between winding and tank
Angle rings (corner rings) and formed end insulation
Cylinders (winding barrels) and core-tube insulation
Spacers, key spacers and strip insulation in the winding
Clamping rings, end rings and washers
Lead supports, connection insulation and tap-changer insulation
Reactor and instrument transformer insulation
Where the board is machined or formed, its high density, good compressibility/recovery and low shrinkage make it well suited to shaped components.
Thermally Upgraded vs Standard Pressboard
| Aspect | Standard pressboard | Thermally upgraded pressboard (this product) |
|---|---|---|
| Thermal-upgrade agent | None | Nitrogen-containing modification |
| Nitrogen (N) content | Not specified | 1.5 – 3.0% (tested 1.78%) |
| Ageing resistance | Baseline | Enhanced - slower cellulose degradation |
| Best for | General insulation duty | High-temperature-loading power transformers, extended-life designs |
| Dielectric strength (in oil) | Adequate | 43.69 kV/mm (this grade) |
FAQ
Q1. What does "thermally upgraded" pressboard mean? It is cellulose pressboard chemically modified with nitrogen-containing compounds to improve its resistance to thermal ageing. The nitrogen (N) content (1.5–3.0%; tested 1.78% here) quantifies the upgrade.
Q2. How is the thermal upgrade verified? By the nitrogen content test - a routine item in the release report. This product's report shows 1.78% N, within the 1.5–3.0% requirement.
Q3. Is this the same as transformer pressboard? Yes - it is a high-density transformer insulation pressboard; the "thermally upgraded" grade adds improved thermal stability for higher-duty applications.
Q4. What thickness is available? This report covers 1.0mm. Other thicknesses and shaped parts are available on request.
Q5. Does it meet the electrical requirements? Electrical breakdown strength tested 13.67 kV/mm in air and 43.69 kV/mm in oil - both above the 12 / 35 kV/mm limits.
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