Leakage Magnetic Field By Simulation And Optimization Of Large Power Transformer

With the development of transformer technology, and in step with the demand of fast-growing power grid, capacity gradually increases in single transformer, hence the eddy loss inthe tank and metal structures caused by magnetic flux leakage of such transformer alsoincreased significantly. Moreover, due to the complexity of leakage magnetic fielddistribution, the eddy loss also distribute unevenly, and lead to extra high loss density in tankand metal structures, which would lead to the hot spot problem, transformer oildecomposition, insulation parts failure, and finally the transformer failure. Therefore, for largecapacity power transformer design, during design phase, careful research on the distributionof leakage magnetic field is a must, for the purpose of controlling of eddy loss, avoiding hotspots.In this thesis, the author studied lots of literature and data, and take one large capacitypower transformer of305MVA/230kV as example, use Infolytica-MagNet software as acalculation tool to build two-dimensional and three-dimensional models, and comparedifferent model after simulation, to see the effect of magnetic shield and magnetic shuntvisually. After comparison between different tank structures, method of cutting tank top andtank bottom is proposed to reduce the cost of materials without increasing loss too much,which is obviously with economic benefit. In the area close to the large current lead, where isfull of high magnetic flux leakage, the non-magnetic steel is proposed to low the eddy loss inturrets, and avoid the overheating problem.Finally measures to optimize leakage magnetic field are presented to avoid variousproblems caused by the leakage magnetic field. These measures are useful in actualengineering: shielding the key area can avoid flux concentrate, effectively reduce the eddyloss, avoid overheating which could cause the potential harm during continuous running,largely improve the reliability and economic of transformer.This paper based on actual engineering, optimization measures are based on simulationresults, and these measures can be used in design stage of large capacity transformers toinstruct engineering practice.