Study On Inrush Current Suppression Method Of No-Load Transformer Based On Controlled Closing

With the expansion of power system,especially the rapid development of wind power technology,power transformer is put into use more and more,the more frequent operation.When the transformer were closed,because the transformer core flux saturation,the existence of remanence and nonlinear characteristics of core material,may produce large amplitude,the inrush current contains the rich harmonics and the DC component,which will lead to the reduction of the service life of the transformer,protective relay misoperation,and reduced power quality and a series of problems,thus suppressing no-load transformer excitation inrush current has very important economic significance.Although the traditional method of inhibition in a certain extent in the electromagnetic transient phenomena,but the investment high cost,complicated operation;put forward and controlled closing technology,suppress the electromagnetic transient phenomenon fundamentally.Because of this paper In order to select relevant technology as the foundation,expand suppression of inrush current transient process and the corresponding control strategy.The intelligent operation of high voltage switch is controlled closing technology,its essence is according to different load characteristics,control of high voltage switch closing in the optimal phase voltage or current angle,opening operation,to achieve a smooth transition without impact.This paper combined with the structure and working principle of the transformer,regardless of the remanence and remanence next,a detailed analysis of the electromagnetic transient process of single-phase transformer no-load closing,expounds the mechanism of inrush current and some important characteristics,and puts forward the basic principle of selection of unloaded transformer.In order to study the basis for our common connection of three-phase transformers,in different remanence case on the closing side for no-load three-phase transformer winding connection of different controlled closing transient process were analyzed,changes in the core flux of no-load transformer is provided.The corresponding selection strategy.In the power system transient simulation software PSCAD based transformer no-load closing model,to choose relevant strategy simulation.The results show that: for different remanence models and different winding connection,using appropriate selection decision-making combination can effectively restrain excitation inrush current.Finally,we build a 10 kV transformer randomly closing and closing dynamic simulation experiment platform,the remanence is zero,the closing phase angle of inrush current and the influence.The experimental results show that: in the peak voltage of closing operation,transformer winding current and normal work of the no-load current size approximately equal to that select closing can effectively restrain excitation inrush current.