Screening And Electrochemical Detection Of Composite Antioxidants In Transformer Oil

Power transformers are key equipment for power transmission and distribution and safe operation of power grids,and the quality of oil-paper insulation directly determines the service life of the transformer.At present,the transmission and distribution technology is developing in the direction of EHV and UHV transmission lines,and the operating conditions of UHV converter transformers are complex,and the voltage level and operating temperature are high,which requires the insulating oil paper have good thermal stability under high temperature.Studies have found that adding composite antioxidants may improve the antioxidant and thermal stability of oils.In this paper,in order to enhance the oxidation stability of transformer oil,different types of antioxidants are selected for thermal aging test.By detecting the physicochemical characteristics of insulating oils under different aging periods,the composite antioxidants with the best thermal stability are selected.At the same time,the optimized electrochemical method was used to detect the content and composition of antioxidants in transformer oil,and a simple,feasible and accurate detection method was obtained.The conclusions are as follows:(1)The DBP,T531,TBHQ and T501 were compounded into the transformer oil and insulating paper,and the aging test tempreature was 130℃.The physical and chemical indicators of oils and papers were regularly detected.With the aging progresses,the deterioration of oils and papers continues to increase,and the different complex antioxidants has different effects on the performance of transformer oil.The order of deterioration degree of insulating oil paper for each group is DBP+T501>TBHQ+T501>T501>T531+T501,the results of TG test showed that T531 had the best thermal stability of antioxidants,and there was a synergistic regeneration mechanism between T501 and T531 molecules,and the antioxidant activity was enhanced after combined use.(2)Differential pulse voltammetry(DPV)was used to detect T501 in oil,and the effects of electrolyte type,concentration,water content and working electrode on the peak current were explored.The results show that the peak current of T5 01 in alkaline solution is much higher than that in acidic and neutral solutions,the optimal electrolyte is KOH,and the optimal electrode is graphite electrode.The response surface optimization test showed that the best test conditions were:KOH concentration of 0.18 mol/L,ethanol water content of 1%,and graphite electrode diameter of 6 mm.When using this method to detect the T501 in actual transformer oil,the peak current response is high,and the accuracy is greatly enhanced,which confirms the high practicability and reliability of the method.(3)Through the optimization test,it was finally determined that the 6mm glassy carbon electrode as the working electrode,the φ1mm platinum wire electrode as the reference electrode,and the 1cm×1cm platinum sheet electrode as the auxiliary electrode.Linear sweep voltammetry(LSV)can be used to simultaneous detection of T501 and T531 in 0.1mol/L KOHethanol solution,and both antioxidants have obvious current peaks.Standard addition recovery experiments and oil aging experiments further proved that this method can simultaneously detect T501 and T531 antioxidants in actual transformer oil detection.