An Efficient and Fast Nondestructive Testing Method for Estimating DP Value of Oil–paper Insulation

The degree of polymerization value (DPv) is a widely recognized indicator of oil–paper insulation degradation in power transformers. However, conventional DPv estimation relies on invasive chemical testing, requiring direct sampling from the transformer, which is impractical for in-service condition monitoring. To overcome this limitation, this study presents a noninvasive and computationally efficient method for DPv estimation based on the interfacial charge characteristics of oil–paper insulation. A quantitative approach is employed, wherein the interfacial charge is derived from polarization–depolarization current (PDC) measurements. The proposed method achieves an estimation accuracy within 3% error, ensuring reliable DPv assessment. Additionally, a qualitative evaluation highlights its ability to eliminate the need for chemical analysis, making it a practical alternative for real-time condition monitoring. The approach is cost-effective, computationally efficient, and suitable for large-scale deployment in transformer maintenance strategies. Furthermore, by eliminating direct transformer sampling, it enhances safety and sustainability while maintaining high accuracy. The method has been validated using experimental data from in-service power transformers, demonstrating its feasibility for practical implementation in insulation health assessment.