The furfural concentration in transformer oil is one of the most important characters to assess ageing condition of insulating paper

and its stability directly determines the reliability of the assessment results. We invetigated the effects of different factors（temperature

copper

and oxygen） on the stability of the furfural in insulating oil. We prepared insulating oil with a certain concentration of furfural

and periodically measured the furfural concentration of the insulating oil to test the stability in different conditions

namely

different temperatures（90

110

130 ℃）

copper（presence or absence）

and oxygen(（presence or absence）. The experimental results demonstrate that

firstly

as far as temperature is concerned

furfural remains stable even when the temperature is raised to 130 ℃

furfural is stable in the absence of copper or oxygen no matter how temperature changes. Secondly

the effect of copper on furfural stability varies with temperature. The stability of furfural is not affected by copper at 90 ℃

however

furfural slowly degrades at 110 ℃ and 130 ℃

and a more rapid degradation is observed at 130 ℃ with a proportion of 19% during 50-day-experiment. Thirdly

the effect of oxygen on the stability of furfural is obvious

and furfural degrades in an oxygen atmosphere. Furthermore

both copper and high temperature are able to accelerate this process. It is a synergistic effect on the stability of furfural among high temperature

copper

and oxygen. The single factor has no or little effect on the concentration of furfural in insulating oil in the absence of the other two factors.