A Strategy Research On Differential Protection Responses To Transient Saturation Of Current Transformers

With the rapid progress ofthe construction of the powergrid, the increasing scale structuremore complex, transient process becomes more complex and diverse, Cthe transientperformance of urrent transformer (TA) are facing greater challenges.The accident sceneanalysis showed that the current transformer core saturation caused by the transientprocessis an important cause of the current differential protection malfunction. Thedifferential protection is usually used as the main protection of electrical equipment, whosemalfunction would constitute a very serious harm to equipment safe and stable operation ofthe system itself. Therefore， the study of transient current transformer’s saturationcharacteristicshas a very important significance.Non-periodic component in the fault current is the main reason that causes transientsaturation of TA. Tasaturation will cause imbalance current of differential current increases,resulting in the error action of differential protection. In this paper, the internal structureofthe different types of current transformers were compared explanation, on this basis, fromthe perspective ofthe electromagnetic characteristics, it analysis in-depth thechanges in thecharacteristics of the various electromagnetic calorimeterin the process of TA saturation,andelaborated on the impact TA saturation will bring to differential protection.This pasper studied the basic principles of modeling and simulation of currenttransformer, using J-A theory in simulation studies of TAmodel. Based on themagnetomotive force equivalent method,used the actual current small transformers indynamic simulation to simulate the transient characteristics of TA saturation.It throughdynamic simulation studyed the largeshort-circuitcurrent transformer saturationcharacteristics of large capacity and decay time constant of the case, and the currenttransformer saturation characteristics in the complexshort-circuitfault conditions (includingconversion failure,external transient fault sandpermanent fault scoincideoutside, etc.); thenestablished simulation models of current transformer saturationin case of said differentcharacteristics.It analyzed secondary current’s waveform characteristics and identification method safter the current transformer saturation. on this theoretical basis, scholars proposed manymeasures for differential protection to resist TA saturation, but these measures inengineering practice there are still many shortcomings. This paper analyzed the differentialprotection malfunction instance, proposed a more effective improvement measure fordifferential protection to resist TA saturation.