抄録
A novel non-destructive diagnosis for medium-sized power transformers have been developed measuring a reflective absorbance of the insulating paper. Generally, the insulating paper gradually turns darker in color during long term use. This coloring is caused by the thermal oxidation of the paper. In this paper, the relationship between the average degree of polymerization of the insulating paper and the reflective absorbance is derived from the accelerated heating experiments using model materials. The values of reflective absorbance at different wavelengths, 600 nm and 800 nm, are used as a diagnostic parameter. The average degree of polymerization is one of the most important parameter to evaluate the life of transformers. We found that the reflective absorbance correlates with the average degree of polymerization of the insulating paper, the correlation coefficient being over 0.70. In this diagnosis, the degree of deterioration of the insulating paper can be calculated quantitatively using the diagnostic master curve, which is obtained from accelerated heating experiments. Using the master curve, the residual lifetime of the insulating paper until breakdown can be estimated theoretically. Therefore, this optical technique is theoretically applicable to residual lifetime diagnosis of power transformers.
