| With the in-depth application of new sensors and communication technologies in the power system,as well as the construction of smart substations,more diversified requirements for the functions of power equipment are put forward,which has caused a series of upsurge in the development of new intelligent power equipment.However,the transient process of power grid often leads to electromagnetic interference of new power equipment,which affects the normal operation of the equipment.In the process of popularization and trial of primary and secondary fusion equipment in distribution network,the faults caused by electromagnetic interference account for the vast majority,and It is difficult to use the previous conducted interference research and protection methods.Therefore,it is necessary to study the disturbance of primary and secondary fusion distribution switch when it is disturbed by the transient radiation magnetic field in the distribution system,and analyze its magnetic field law,which has important theoretical and engineering value for improving the application reliability of such equipment.Firstly,the electromagnetic transient model of typical primary and secondary fusion distribution switch is established in this paper.According to the existing research,the frequency characteristics of transient interference signal are summarized,and the finite integral time domain(FITD)method,which is suitable for the calculation of radiated electromagnetic field of primary and secondary fusion switch,is selected.Taking the simulated interruption of arcing,lightning current impact and inrush current of switching capacitor as interference sources,the spatial magnetic field distribution of distribution switch under these three interference sources is calculated,and the characteristics of spatial magnetic field near electronic transformer are analyzed.Then,the electromagnetic interference test platform of primary and secondary fusion distribution switch is designed in the laboratory,and the lightning voltage,lightning current and simulated arc breaking tests are carried out on a certain type of primary and secondary fusion column switch,and the magnetic field intensity is measured to verify the correctness of the electromagnetic transient model to solve the spatial radiation magnetic field.In order to further study the influence of space radiated magnetic field on switch secondary sensitive devices,a secondary circuit model with electronic transformer merging unit board as the core is established,and a system level electromagnetic calculation model is formed,which includes column circuit breaker,distribution terminal(FTU)shell and internal board.Thirdly,the shielding effectiveness of FTU shell under three kinds of transient electromagnetic interference is analyzed.It is proved that the shielding frequency band of the shell used in the existing engineering is limited and can not protect the internal devices well;The transient voltage and current of the 3.3V power line on the merging unit board are calculated by using the frequency scaled finite integral method in time domain.The results show that the amplitude of the transient voltage and current under the interference of lightning stroke and inrush current is larger than the tolerance standard of the port.Finally,according to the characteristics of radiated magnetic field interference,three protection optimization methods considering installation distance,angle and shielding layer are proposed.The comparison shows that the above protection methods can weaken the interference of transient radiated magnetic field on the secondary circuit in varying degrees,which is helpful to improve the electromagnetic compatibility performance of primary and secondary fusion switch in practical engineering. |
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