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Unformatted text preview: 1962 IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 20, NO. 3, JULY 2005 On the Estimation of Elapsed Life of Oil-Immersed Power Transformers Manoj Kumar Pradhan , Student Member, IEEE, and T. S. Ramu Abstract— Inadvertent failure of power transformers has se- rious consequences on the system reliability, economics, and the revenue accrual. An accurate estimation of transformer life can, to a very large extent, mitigate the problems, besides satisfying the conflicting requirements of optimum utilization of the equipment and safeguarding the reliability. In this endeavour, the authors have planned long duration aging experiments on scaled-down (prorated) models  of a transformer, incorporating all of the essential features of actual equipment under normal operating electric stress and accelerated thermal stress. In continuation of the authors’ earlier experi- mental investigations, an elapsed life assessment study has been instituted by acquiring insulation-aging data under accelerated thermal stresses. Index Terms— Carbon oxides, degree of polymerization, elapsed life, empirical model, furfurals, transformer insulation. NOMENCLATURE Specific reaction rate. Frequency factor, defined in (1). Model coefficients in (9). Degradation parameter, defined in (2). AAF Accelerated aging factor. Equivalent accelerated aging factor. AF 2-Acetylefuran dissolved in oil (in ). BDVO Breakdown voltage of oil (in kilovolts). BDVP Breakdown voltage of paper (in kilovolts). Constant term in (9). Correlation coefficients. CO Carbon monoxide dissolved in oil (in ppm). Carbon dioxide dissolved in oil (in ppm). COx Carbon oxides (CO, ) dissolved in oil (in ppm). DF Dissipation factor. DGA Dissolved gas analysis. DP Degree of polymerization. DTCM Diagnostic testing and condition monitoring. Activation energy of the aging process. EOL End of life of power transformer. FA Furfuryle Alcohol dissolved in oil (in ). FD 2-Furaldehyde dissolved in oil (in ). FTIR Fourier transform infrared detector. GG Gas generation. HM2F 5-Hydroxymethyle-2-Furfural dissolved in oil (in ). Manuscript received June 23, 2004; revised October 18, 2004. Paper no. TPWRD-00293-2004. The authors are with the Department of High Voltage Engineering, Indian In- stitute of Science, Bangalore 560012, India (e-mail: [email protected]). Digital Object Identifier 10.1109/TPWRD.2005.848663 HPLC High-performance liquid chromatograph. HST Hottest spot temperature (in degrees Celsius). M2F 5-Methyle-2-Furfural dissolved in oil (in g/kg). OIP Oil-impregnated paper. particle Micro particle count. PD Partial discharge. ppb Parts per billion. T Absolute temperature (in degree Kelvin). TCG Total combustion gases dissolved in oil (in ppm)....
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- Spring '11
- INDIAN INSTITUTE, Indian Institute of Technology Kanpur, IEEE Xplore, power transformers