Saturation Characteristics Of Current Transformer And Its Influence On Protection Ability

Electromagnetic current transformer,as the standard of protection and measurement of transmission equipment,has been widely used in power system.With the expansion of power grid,the short circuit current increases year by year.At present,V 110 k has been built and the following system protection with the vast majority of current transformers using electromagnetic current transformer.Because of the nonlinear electromagnetic iron core transformer,when the short-circuit current is greater than even greater than the rated accuracy limit primary current,current transformer saturation will occur resulting composite error.When the distortion caused by the saturation of the current transformer is two times,it will be sent to the relay protection device,which will cause the protection malfunction,which will seriously threaten the power supply reliability of the system.In this thesis,the saturation characteristics of the protection type electromagnetic current transformer and its influence on the protection ability are studied in this thesis.Through the LTspice IV simulation software to establish the model of current transformer excitation curve based on the in-depth study of the impact of fault current,current transformer two load,core area size,average path length,core current transformer ratio,core saturation magnetic flux density and core remanence and other factors on the core saturation condition.The experimental test platform of the current transformer is established,and the saturation characteristic and the protection performance of the current transformer are tested.The magnetic energy of the iron core was tested by experiment,and the current transformer's volt ampere characteristic test was carried out.The characteristic curve of the iron core was drawn and the saturation voltage was found,and the simulation results were compared with the simulation results.The accuracy of the model is verified by comparing the theoretical study,simulation test and field test,and the accuracy of the model is verified by comparing the simulation results with the experimental results.In this thesis,based on the current transformer saturation mechanism and the simulation and experiment,the factors that affect the saturation of current transformer are analyzed.The effects of different parameters on the two side error ofthe current transformer are studied,and the magnetic properties and saturation characteristics of the magnetic core of the current transformer are analyzed.