Study On The Influential Factors Of The Furfural Content In Transformer Oil

Power transformer is one of the most important equipment in the power system,and it operates safely or not is directly related to the safety of the system.The insulation system of the transformers is mainly composed of compound insulation system which is made up by insulating oil and insulation paper.When the transformers works,their insulation paper and insulating oil ages gradually with the effect of temperature,oxygen and other factors.Statistics show that more than 90% of the transformer failure caused by the insulation aging,therefore,timely and accurate aging assessment is of great significance for safe and reliable operation of the transformer.As one of the aging assessment methods for transformers,furfural has the advantages of simple sampling,accurate detection and intimate relationship with the aging extent of the solid insulation,so it is an important way to evaluate the aging extent of the transformer.However,there is a gap between the assessment model obtained in laboratory and the data from the field-transformers.This paper analyzes the differences between the aging in laboratory and the aging in the field firstly,and considers the generation and disappearance of furfural,three aspects was researched,including:1)the effect of temperature on the aging assessment of transformers by furfural;2)the effect of moisture and antioxidant on the aging assessment of transformers by furfural;3)the stability of furfural under different conditions.Following is the main achievements of this thesis:(1)Thermal aging experiments at 100 ~ 130 ? were conducted,and the DP of the paper and the furfural content in oil and paer were measured.The development process of furfural production as well as the diffusion process of furfural was analyzed,which led to the decrease of the furfural content in the insulating oil at initial aging period when the temperature is ralatively high.Moreover,the temperature plays a role on the production of furfural,and higher temperature means more amount of furfural produced,which indicates that the production of furfural produced by field-transformer is less than that the production of furfural produced in labotory when DP decreases to the same extent.(2)The effects of moisture and DBPC on the production of furfural were analyzed by thermal aging experiments with different initial moisture content or different DBPC concentrations in oil.Both moisture and antioxidant will result in an increasing production of furfural.In the relatively low initial moisture content range(0.55~0.97%),furfural production enhances 11.8% for each 0.1% additional moisture;As for DBPC,the amount of furfural increased 6.95% with 0.1% of extra antioxidant.The moisture content of paper affect the distribution of furfural between insulating oil and paper as well,and it results in the migration of furfural from paper to insulating oil.In this paper,it is concluded that the main reason leading to increasing of furfural by water and DBPC is that the hydrolysis leads to more complete decomposition of cellulose.(3)The stability of furfural was further studied,and the results show that the stability of furfural is not affected by temperature or copper.The degradation of furfural content in oil of field-transformer is mainly affected by oxygen.The aging experiment under aerobic condition shows that oxygen has a great effect on the content of furfural in oil.Considering that free-breathing transformers may introduce oxygen leading to furfural degradation,so the aging assessment model by furfural for fully sealed transformers and free-breathing transformers should be established separately.