Improved Moisture Analysis of Power Transformers using Dielectric Response Methods

摘要

The three commercialised dielectricrndiagnostic methods RVM with analysis software SWRVM 2 V.3.0, PDC with PDC Evaluation Software V.3.0 and FDS with analysis software MODS V. 1.5 were systematically benchmarked. Based on the achieved results a new software was developed, likewise benchmarked and applied for an onsite measurement.rn1. The commercial evaluation software for PDC and FDS are able to compensate for the influences of insulation geometry, insulation temperature and oil conductivity.rn2. The commercial analysis software for the RV method based on the central time constant is too simplistic.rn3. All methods show an apparently decreasing moisture analysis result for increasing temperature and an increasing moisture result for increasing oil conductivity.rn4. A new measurement instrument "Dirana" was developed, that combines the time and frequency domain measurement and thus decreases the time need essentially.rn5. The new software bases on a new data pool, measured at new and aged pressboard with various moisture contents and oil impregnation.rn6. The new analysis algorithm compares measurements from a transformer to modelled dielectric responses, obtained from the so-called XY-model. The new software features weighting of low frequency data and compensates for conductive aging byproducts.rn7. Applied on the benchmarktestthe new software proves the best compensation for oil conductivity and for insulation geometry.rn8. The new software was successfully utilized for onsite measurements in comparison to other measurement and analysis methods.