| Petroleum-based transformer oil can act as an insulator or electrolyte depending on the concentration of charges in the oil. The availability of charges for conduction influences the level of voltage breakdown in the mineral oil and depends on the intensity of physico-chemical processes such as redox action, hydrolysis, photodegradation, sludge/particle development, and gas formation arising from thermal, mechanical, chemical, and electrical stresses in the oil. Previous investigators have focused mostly on single indicators of oil aging to build models for analyzing the aging pattern of transformer oils within timeframes that are too short relative to the operational service life of transformers. In this research, the interdependence of oil voltage breakdown and changes in T14 and T24 transformer oil physico-chemical characteristics are investigated experimentally. The calculated activation energies are 26.2 KJm-3 for T24 and 25.4 KJm-3 for T14 oils. Using experimental data on oil degradation under typical transformer operating conditions, the service lives of T14 and T24 transformers are estimated as 40 and 43 years, respectively. Oil degradation constants are determined to be 7.38 x 10-12 L-1 s-1 and 6.98 x 10-12 L-1 s-1 for T14 and T24, respectively. During aging of both oils at the temperature of 60°C for five days, biogenic crystallite evolved as exsolution product on the internal walls of the oil container. Data from this study can be used for design, planning, budgeting, maintenance, and risk evaluation, making it very relevant to practical applications for transformer evaluation. |
