Research On Immunity Characteristics Of Electronic Transformer In Complex Electromagnetic Environment Of Substation

Due to the electronic transformer is installed between the primary equipment,the secondary equipment such as signal acquisition unit and merging unit are in the complex electromagnetic environment of the substation,which will lead to the frequent occurrence of electromagnetic interference faults of the electronic transformer in the operation of the grid.Among them,the very fast transient over-voltage(VFTO)generated by disconnector opening and closing no-load bus has the strongest electromagnetic interference on electronic transformer,which is the main factor of electronic transformer fault.Therefore,it has important theoretical significance and engineering application value to study the immunity characteristics of electronic transformer to electromagnetic interference caused by VFTO.Based on the analysis idea of disturbance source coupling path disturbed equipment,this paper studies the generation mechanism of VFTO and the major coupling mode of interference,and conducts the laboratory research on the immunity performance of electronic transformer to VFTO induced electromagnetic interference.The specific research work is as follows:First of all,based on the 110 k V AIS disconnector open and close capacitive small current test platform,a broadband equivalent model of the test platform is established,and the correctness of the theoretical model is verified by Simulink simulation and test platform measurement.Further analysis shows that the main interference to the electronic transformer is the transient over-voltage at the capacitance port of the low-voltage arm of the capacitor voltage divider and the transient ground potential rise caused by the existence of the earth inductance.Both of them are in the form of damped oscillation wave,but the main frequency of the oscillation is quite different.Secondly,the sources of differential mode and common mode interference at the signal port of electronic transformer acquisition unit are analyzed,and the specific coupling path of signal line interference current is L-N(differential mode)and N-PE(common mode),and the interference current of L line and N line is quite different.Furthermore,the correctness of the coupling path analysis is verified by the test platform and the Simulink simulation model.Finally,on the basis of the above research on interference source and coupling path,in order to study the immunity characteristics of electronic transformer to interference,and to promote the improvement of electromagnetic compatibility testing standard of electronic transformer,this paper proposes a interference simulation scheme with high frequency damped oscillation wave as interference source and L-N and N-PE injection mode,to study the acquisition under different frequency and voltage level Immunity characteristics of the unit.The results show that the interference immunity of the acquisition unit to different frequencies is quite different,the degree of interference is proportional to the interference voltage,and the high and low temperature will affect the immunity of the acquisition unit to a certain extent.