Investigation Of Moisture Effect on Breakdown Voltage of Aged Trasnformer Oil

Ng, Vincent (2026) Investigation Of Moisture Effect on Breakdown Voltage of Aged Trasnformer Oil. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

This study investigates the influence of moisture content and electrode gap distance on the breakdown voltage (BDV) of aged mineral transformer oil using a combined experimental–simulation approach. BDV tests were conducted in accordance with ASTM D1816 using a BAUR DPA 75C across six moisture ranges (6-10ppm, 11-15ppm, 16-20ppm, 21-25ppm, 26-30ppm, >31ppm) and two gap configurations (1 mm and 2 mm), each with 50 readings to ensure statistical reliability. Results showed a clear inverse relationship between moisture and BDV, with reductions of up to 54% observed at higher moisture levels. Electrostatic simulations were performed using ANSYS Maxwell to evaluate electric field behaviour under varying material permittivity; however, the peak field remained constant due to solver assumptions of homogeneous dielectric media. To overcome this, empirical equations were applied using constant electric field values and moisture-adjusted dielectric strength to estimate BDV, achieving close agreement with experimental results mostly within ±20%. Power-law models were fitted to enable rapid prediction of BDV across different moisture levels and gap distances. The findings highlight both the degradation effect of moisture and the mitigating role of geometric spacing, providing practical guidance for insulation coordination in oil-filled equipment. Limitations of the simulation model and future improvement paths are also discussed