Study On The Influence Of The Invade Wave To Transformer Insulation

As a core equipment within the substation,security issues of transformer must be taken seriously.However,during the field operation,the transformer will suffer from unexpected insulation incidents with no sign.One of the reasons is that the transformer in the substation,the switching operation,lightning intrusion waves and other transient over-voltage impact on the transformer accumulatively.This caused equipment insulation deterioration,and then lead to sudden accidents.And this topic gradually become an important part of transformer insulation research.In the existing research,there are few studies focus on the effect of the cumulative effect to the transformer insulation or the distribution of intruding wave among the substation.And method for assessing the damage of intrusion waves is needed.In view of this problem,this paper has carried out the following three aspects:Firstly,according to the electrical characteristics of each equipment in the substation,the modeling method used in the simulation calculation is analyzed theoretically.Including the intrusion wave model,the transmission line model and the numerical simulation of the equipment inside the substation.The simulation model of ATP-EMTP was established,and the distribution of over-voltage among the equipment inside the substation was analyzed based on the invasive wave measured.Secondly,through the laboratory test,the cumulative effect of intrusion wave on the insulation degradation of the transformer was studied.The cumulative impact characteristic of the 500 k V transformer winding model is studied and the V-N characteristic curve is drawn.The influence of the times of invasions on the breakdown voltage of the oil-paper insulation model is analyzed from the experimental and theoretical points of view.At last,Time Domain Waveform Conversion(TDWC),Time Domain Severity Factor(TDSF)and Frequency Domain Severity Factor(FDSF)three methods for assessing the damage of intrusion waves is studied.Then,S-transform and the traditional F-transform are compared,and the FDSF evaluation method is improved by using the S-transform technique,which is realized by MATLAB programming.