Research On Detection Technology Of DC Resistance Of Current Transformer

Current transformer is an important transmission device in power system.With the construction of a large number of transmission lines in China,the development of long-distance transmission lines,the gradual implementation of the national networking strategy as well as the gradually increase of electrification of railway,electroplating,steel,aluminum and other electricity load.It is inevitable that there will be a certain amount of DC component in the power system.DC component in the transformer and even current transformer will produce DC bias phenomenon.DC magnetic bias will seriously affect the transmission characteristics of the current transformer,which will cause serious consequences to the stable operation of the power system,and bring unfair and unreasonable results.Therefore,the research on the detection technology of the DC resistance of the current transformer has important practical significance.Through the research and analysis,this article has carried on the related work.Firstly,the excitation characteristic model of CT core is established,and the calculation formula of the transmission error of CT under the influence of DC component is derived by the equivalent model of CT under DC bias.The transmission characteristics of CT before and after the DC component are compared and analyzed,and the influence of the load DC component on the primary current of the medium voltage distribution network is further analyzed.Secondly,based on the different current source,three kinds of different DC current transformer performance test methods are proposed.Especially in the analysis and research,it is found that the method based on proportional DC superposition method has the advantages of simple,economical,scientific,practical,strong operability,low cost and so on.In addition,a set of testing device for the performance of the current transformer is designed by the modular test,which provides a practical basis for the research.Thirdly,through the two kinds of input mode of small voltage and high current,the design of the anti DC performance test scheme of the current transformer is designed,so that the detection scheme is efficient,reliable and authoritative.Finally,by using the comparative analysis method to design a network operation scheme,anti DC transformer operation,further demonstrate the accuracy performance of the current transformer DC resistance of the test in the actual operation.