| In recent years,with the intelligent development of gas insulated substation（Gas Insulated Substation,GIS）,electronic transformers have been widely used in GIS by virtue of their small size,low energy consumption and frequency bandwidth.Due to its local installation mode,the electronic transformer directly operates on the substation site with complex electromagnetic environment,especially the ultra-fast transient phenomenon caused by the operation of the GIS isolation switch will provoke the electromagnetic field of the transient space,which in turn causes severe electromagnetic interference to the electronic transformer in a conductive or radiative coupling manner,resulting in damage to its sensitive equipment,and ultimately poses a threat to the safe operation of the GIS.Therefore,the problem of GIS transient overvoltage and its electromagnetic interference to electronic transformers is worthy of in-depth study.Based on the research and calculation of GIS transient overvoltage,a three-dimensional model of GIS-connected electronic transformer is established,the electromagnetic interference distribution and influence of the spatial electromagnetic field associated with transient overvoltage on electronic transformers are simulated and calculated,and the electromagnetic shielding structure optimization of the electronic transformer collection box is simulated and analyzed.The main research content of the article is as follows:This paper studies the ultra-fast transient phenomenon under GIS isolation switch operation and the establishment of transient circuit model.The theory analyzes the mechanism and classification of GIS ultra-fast transient phenomenon,further analyzes the coupling pathway and influence of ultra-fast transient phenomenon on the electromagnetic interference of GIS electronic transformer,and constructs a GIS isolation switch operation transient circuit model to calculate the transient overvoltage.The calculation results show that the peak of the line overvoltage is generated on the power side of the circuit breaker,which is 875.69 k V,and the transient voltage amplitude and frequency are high,and the threat to the electronic transformer cannot be ignored.The spatial electromagnetic field distribution of GIS-connected electronic transformers is studied under the action of ultra-fast transient overvoltage.The spatial simulation model of GISconnected electronic transformer is established by using electromagnetic transient simulation software,and the space electromagnetic field of radiation entering the electronic transformer collection box is calculated and analyzed.The simulation results show that the transient overvoltage associated electromagnetic field can penetrate the terminals to reach the inside of the transformer collection box and generate electromagnetic interference,and the frequency component of the radiated electromagnetic field is basically the same as that of the internal electromagnetic field frequency of GIS,and the degree of electromagnetic field radiation leakage gradually strengthens with the increase of frequency composition,and the typical position inside the GIS pipeline and the internal of the electronic transformer collection box reaches the maximum electromagnetic field intensity at a frequency of 28.547 MHz.By decomposing the electromagnetic field intensity on three different coordinate axes,the radiation interference intensity in the z-axis direction inside the collection box is relatively small.The effect of the electronic transformer collection box structure on the inhibition effect of the internal radiated electromagnetic field was studied.The simulation model of the metal collection box of six structures is constructed,and the electromagnetic field strength distribution and electromagnetic shielding efficiency of different structures of the collection box are calculated by simulation.The simulation results show that the electric field shielding efficiency of the aluminum metal shell of the electronic transformer is 18.67 d B,and the magnetic field shielding efficiency is13.56 d B;for the different structures of the collection box,in the case of the total area of the connection terminal holes,the porous structure has a significant inhibition effect on the internal electromagnetic field,and the five porous structures meet the requirements of the second level of screen efficiency,and the more the number of holes,the better the inhibition effect;in addition,the double-layer structure has the effect of further inhibiting the radiated electromagnetic field. |
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