Development of Non-Destructive Optical Diagnostic Apparatus for Pole Transformers

Abstract

In this study, we found that the reflective absorbance correlates with the average degree of polymerization of the insulating paper, the correlation coefficient being over 0.90. It was found out that the optical diagnostic method could be applied in the core degradation diagnosis of a pole transformer, and the indirect degradation diagnostic apparatus of the pole transformer using this technique was developed. Optical diagnostics is a method of analysis by presuming the degree of proceeding of the heat deterioration of the organic insulator from the difference in reflective absorbance of two wavelengths containing near-infrared light, and the life prediction is also possible by using chemical kinetics. 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 based on the chemical kinetics. The optical sensor consists of two kinds of optical fiber cables to attach and measure the reflective absorbance on the insulating papers in the oil, two kinds of near-IR (infrared) laser diodes (LD), 830nm and 1310nm, as light sources, and a photodiode as a detector, and so it is very compact and lightweight (less than 1.5kg).