Research on on-line DGA using FTIR [power transformer insulation testing]

Electrochemical sensors and gas chromatography are widely used in online monitors for dissolved gas-in-oil of power transformers, but some fatal defects exist. In view of the many advantages of FTIR, the basics of applying it on such monitors are studied and the results are presented. Investigation shows that all the characteristic peaks needed to be analyzed can be covered if the measurable wavenumber region of the spectrometer is 720 cm^-1∼3400 cm^-1, and the optimum optical length of the gas cell is around 150 mm. Comparative results demonstrate that absorption spectra obtained by wavelet transmission are consistent to those with their real back ground divided and are independent on spectrometers. It is concluded that such a monitor can be constructed using FTIR that can precisely detect all the diagnostic gases except hydrogen and are free of consuming gases as well as in situ calibration.