Research On Identification And Suppression Technology Of Transformer Magnetizing Inrush Based On PSCAD

The power supply of Tongliao City has shown a tight trendwith the rapid economic development in recent years.The substation is play an important role in the power system,and the transformer capacity is used as a standard to measure the power supply level of the local.Based on the situation that the capacity of No.1 main transformer in the local 220 kV substation is too small,the main transformer needs to be replaced to meet the local power supply.The transformer is essential to the entire power system.Its operating state is closely related to the protection device.The power system stability is affected by transformer protection devices.Reliable and effective relay protection system is particularly important.Based on the background,this paper will carry out related researches on the identification and suppression of transformer magnetizing inrush current.This article first theoretically analyzes the generation and characteristics of transformer magnetizing inrush current,reveals the law of the transformer,and then explains the basic principles of transformer differential protection.Subsequently,the PSCAD/EMTDC software was used to construct the no-load closing models of single-phase and three-phase transformers,and the influence of residual magnetism and initial phase angle on the inrush current were investigated.Then,the advantages and disadvantages of these methods are analyzed.Because the second harmonic content of the zero-sequence current generated by the asymmetrical inrush current is relatively high,the second harmonic content of the zero-sequence current is considered as the criterion for identifying the excitation inrush current,and the feasibility of operation under different operating conditions is explored by PSCAD /EMTDC.Finally,considering the harm of excitation inrush current,this paper proposes a method of suppressing excitation inrush current based on the closing strategy,and then examines the suppression of transformer excitation inrush current from two aspects of synchronous closing and split phase closing.The Simulation show that the method based on the second harmonic content of the zero-sequence current can accurately distinguish the excitation inrush current and the transformer fault current,which can enable the system to correctly lock or open the transformer differential protection.It provides guarantee for the reliable operation of the transformer protection.At the same time,the split-phase closing strategy can play a better role in suppressing the inrush current,which will further reduce the adverse effects of the inrush current on the transformer,and better guarantee the reliable and stable operation of the power system.This article not only provides a theoretical reference for thedevelopment of the project,but also will accumulate experience for the in-depth study of excitation inrush current.