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Keywords
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condition assessment, degree of polymerization, furan Analysis, paper insulation, spectral response, transformer oil
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Abstract
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Measuring the furan concentration in transformer oil is one of the most common methods of monitoring and evaluating insulation paper and estimating its degree of polymerization. In this paper, methods for measuring furan concentration, especially the ultraviolet-visible spectroscopy method, are reviewed on the old transformers oil. The results show that the excessive turbidity of old oils and noise at low wavelengths are the main disadvantages of this method, which reduces the accuracy of the measurement. To overcome these disadvantages, two solutions are proposed: a) Diluting insulation oil with hexane to reduce adsorption intensity, b) using average adsorption at a given wavelength to reduce noise impact. The proposed solutions are applied to the oil sample of 5 old distribution transformers, and a mathematical equation for calculating the concentration based on the average absorption at a wavelength of 190 - 600 nm is presented. To reduce the test time, a wavelength of 190 - 400 nm has been suggested as the optimal wavelength for measurement. The results show that the average difference between the values of degree of polymerization in the proposed method and the direct measurement method is equal to 77.5 units.
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