Study On Current Transformer Modelling And Saturation Identification Based On Dynamic Regional Saturation

With the rapid development of power grid,the increase of short circuit capacity of the power grid,the more complex fault transient characteristics and the harmonics from the new energy intergration,the transient saturation of the protective current transformer is easier to occur,which makes the reliable operation of the relay protection face the severe challenge.Therefore,it is of great theoretical significance and application value to study the transient model of the current transformer from the transient saturation mechanism to reduce the hidden danger in the protection operation.In this paper,the idea of regional saturation is introduced to improve the dynamic J-A current transformer model.It emphasizes the excess loss of the core under transient conditions,and designs a numerical solution for the proposed dynamic regional saturation J-A current transformer model without iterative format,so that it can simulate the two side output of the current transformer on line.Based on the analysis of the basic transient characteristics of the P current transformer,the dynamic simulation test of the current transformer is studied and carried out.The maximum transient current period component value is up to 48kA,and the related problems such as the time frequency characteristic and the influence factors of the transient saturation are analyzed empirically.Then,facing the reality that transient saturation is liable to cause mal operation of protection,the research and application of saturation suppression is carried out.The saturation recognition plays a role in the scheme based on the improved gradient mathematical morphology.A fixed scale sliding data window is constructed to detect the saturation information in real time,extract the unsaturated data segment and form a protection criterion.Finally,by the plenty test data which are actually saturated in the flow test,the proposed dynamic partitioned saturation J-A model,the static J-A model and the dynamic J-A model are verified respectively.A large number of results prove the effectiveness of the proposed method.At the same time,the propased model is used to establish a the current transformer simulation experiment,both the simulation and field test data are used in the saturation suppression test.It is proved that the saturation suppression scheme can quickly and reliably identify the saturation form in the multi transient saturation level,steady state saturation recognition and transient unsaturation,and provide a guarantee for the reliable operation of the protection system.