Influential Factors and Correction Method of Furfural Content in Transformer Oil

Abstract

Furfural content in transformer oil is considered a credible method to evaluate the aging extent of insulation paper and is extensively applied to the aging assessment of insulation system in transformers. Clearly, the accuracy of furfural analysis is directly related to the stability of furfural in oil, which, nevertheless, may be affected by various factors. In this research, furfural was added to insulation oil directly to analyze its stability in oil firstly. Furfural contents in different conditions, such as different temperatures, copper, and oxygen atmosphere, are measured regularly. The results corroborate that the furfural content in the oil keeps constant when the oil temperature is less than 130 • C without copper or oxygen; copper cannot make furfural in oil degrade without oxygen when the temperature is below 90 • C. These results indicate that the furfural is stable at the common operating temperature of transformer oil (40 • C ∼ 70 • C) as long as no oxygen is in oil. Oxygen is the main degradation cause of furfural in oil, and high temperature and copper accelerate this progress. The oxidation product of furfural in oil has been explored, which shows that the furoic acid is the main degradation product of furfural when the temperature is less than 90 • C. Thus, the furoic acid content in oil can be measured as a reference to increase the accuracy of the furfural analysis.

Thermally Accelerated Aging of Insulation Paper for Transformers with Different Insulating Liquids

“…For this reason, there is an attempt to determine the DP value via the determination of aging markers in the insulating liquid, such as with the measurement of the furan concentration, whereby the DP value of the paper is indirectly inferred via algorithms [14][15][16]. However, fluctuations in furan concentration may occur during operation [17,18]. Furthermore, this is also influenced by the type of insulating liquid, which can affect the accuracy of the DP value calculation [19].…”

Microcosmic mechanism and correction of moisture effect on furfural diffusion and equilibrium in oil‐paper insulation

“…Among all the above‐mentioned methods, furfural analysis is regarded as an effective evaluation method because furfural is peculiar to the ageing process of insulation paper. Considering that the insulation paper is difficult to be repaired or replaced in the whole lifespan, it is the weak point of oil‐paper insulation and determines the insulation life [12, 13]. Plenty of studies have been conducted on the transformers' ageing assessment with furfural content in oil in recent years.…”

“…To date, lots of methods are proposed for the ageing assessment of transformers, including dissolved gas analysis, furfural analysis, frequency-domain spectroscopy, and so on, which are a benefit to perceiving the states of transformers [8][9][10][11].Among all the above-mentioned methods, furfural analysis is regarded as an effective evaluation method because furfural is peculiar to the ageing process of insulation paper. Considering that the insulation paper is difficult to be repaired or replaced in the whole lifespan, it is the weak point of oil-paper insulation and determines the insulation life [12,13]. Plenty of This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.…”