| Electronic transformer is widely used in GIS intelligent substation because of its small size,low energy consumption,wide frequency band and other advantages.Its local installation mode breaks the boundary between the traditional primary equipment and secondary equipment,and directly places the signal acquisition circuit in the substation site with complex electromagnetic environment.Because the sensor circuit and the acquisition circuit work in a complex and high-intensity electromagnetic environment for a long time and a short distance,they often breakdown in the process of operation.Especially when the disconnector is operated in GIS,due to the slow moving speed of the contact and the absence of arc extinguishing device and other factors,it will produce more serious extremely fast transient phenomenon.Electromagnetic interference will cause serious threat to the electronic transformer through conduction,radiation or the combination of the two,resulting in the breakdown,signal distortion and other phenomena of the transformer.Therefore,it's meaningful to the analysis of electromagnetic interference of electronic transformer and the research of anti-interference methods of electronic transformer.In this paper,a 550 kV GIS substation is taken as the research object.Based on the principle of transient electromagnetic interference caused by the operation of disconnector,the electromagnetic interference path of electronic transformer is determined and the corresponding anti-interference method is proposed.The specific work is as follows:(1)The interference analysis of electronic transformer are introduced and a transient model of disconnector operation is built.Based on the theoretical analysis of the generation mechanism,classification and basic characteristics of the very fast transient phenomenon,a transient model of disconnector operation is built,which is verified by simulation with the data of a test platform,and the influencing factors of the very fast transient phenomenon are analyzed.(2)The anti-interference method of electronic current transformer is studied.For Rogowski coil type electronic current transformer,the high frequency equivalent models of lumped parameters and distributed parameters of Rogowski coil are established respectively.By comparing the simulation results with the measured data,it is clear that the output induced voltage of Rogowski coil distributed parameter model is more in line with the actual situation in the spectrum distribution and peak value,and can reflect the electromagnetic transient process on Rogowski coil more accurately and truly,Finally,the suppression effect of lowpass filter and over-voltage protection device on output over-voltage of Rogowski coil is studied.(3)The anti-interference method of electronic voltage transformer is studied.In view of the over-voltage on the bus at the sensor unit of the voltage transformer,the paper puts forward that the very fast transient overvoltage(VFTO)can be controlled by metal oxide arrester(MOA),the dominant frequency component is suppressed to the maximum extent to achieve the purpose of maximum efficiency suppression of VFTO peak,and the optimal position of MOA is determined by analyzing the relationship between the position of MOA and the amplitude of dominant frequency component.At the same time,the high-frequency transmission characteristics of the sensor unit are studied.Considering its stability and transient measurement accuracy,particle swarm optimization algorithm is proposed to optimize its electrical parameters,which can effectively improve the transmission characteristics of the voltage divider and reduce the peak output overvoltage.Finally,the anti-interference method of combining two-stage RC filter and over-voltage protection diode is proposed for the over-voltage signal of the input the acquisition unit,which is verified by simulation and the measurement accuracy of the combined circuit is studied and calculated. |
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