What Is Degree of Polymerization?
Degree of Polymerization refers to the average number of glucose units in the cellulose molecular chain. It directly correlates with the mechanical strength of the paper and pressboard used in transformer insulation. Higher DP values indicate new or healthy insulation, while lower values reflect aging and degradation.
Test Standard
ASTM D4243 – Standard Test Method for Measurement of Average Viscometric Degree of Polymerization of New and Aged Electrical Papers and Boards
Test Method Summary
- Cellulose sample (paper or pressboard) is dissolved in cupriethylene diamine (CED) solution
- Solution viscosity is measured using a capillary viscometer
- Degree of Polymerization is calculated based on intrinsic viscosity
Key Gases Measured
Insulating Liquids – Measurement of Relative Permittivity, Dissipation Factor (Tan δ) and DC Resistivity.
| DP Value Range | Insulation Condition | Recommendation |
|---|---|---|
| > 1000 | New / Excellent | Suitable for long-term use |
| 800 – 1000 | Good | Acceptable with monitoring |
| 500 – 800 | Aged | Monitor closely or plan drying |
| < 500 | Critically Degraded | Recommend replacement/refurbishment |
Why DP Testing Matters
- Accurate indicator of insulation aging
- Predicts mechanical failure and loss of dielectric strength
- Supports condition-based maintenance strategies
- Helps evaluate reclaimed transformers or second-hand units
- Essential for RLA (Remaining Life Assessment) and end-of-life planning
Our Testing Advantages
- ASTM D4243-compliant DP analysis for paper & pressboard
- NABL-grade viscometry lab and calibrated equipment
- Minimal sample required (as small as 1g)
- AI-enhanced ERP platform for long-term insulation trend tracking
- Technical consultation for life expectancy estimation
Report Includes
- Measured Degree of Polymerization (average DP value)
- Condition classification (New / Good / Aged / Critical)
- Comments on mechanical integrity and insulation brittleness
- Comparison with IEC/IEEE threshold values (if applicable)
- Actionable maintenance or replacement recommendations
Applications
- Power and distribution transformers
- Shunt reactors and HV equipment
- Dry-type and oil-immersed transformers
- Failure analysis and forensic testing
- OEM quality assurance and transformer refurbishing
Why Choose Tru-FIL?
- Experienced insulation material analysis lab
- 24/7 testing capability and rapid turnaround time
- Sample pickup across India using barcode-sealed kits
- Trusted by OEMs, utilities, and EPC contractors
- ERP-integrated reporting and compliance documentation