Fig. 1. Principle of transformer insulating oil quality testing based on fluorescence double color ratio

Fig. 2. The principle of transformer insulating oil quality testing based on fluorescence double color ratio

Fig. 3. Fluorescence spectra of the fresh oil on scanning excitation wavelengths

Fig. 4. Selection of optimal fixed excitation wavelength
(a): Comparison of fluorescence characteristics of samples; (b): Intensity curves of characteristic peaks at each excitation wavelength; (c): Variance curves of characteristic peaks at each excitation wavelength

Fig. 5. Curve of fluorescence proportional diagnostic model for discharge breakdown of transformer insulated oil