| In the wake of the rapid development of Chinese electric power system, the power grid continues to expand. Power transmission systems in 500 kV occupied a dominant position in Chinese electric power system. Nowadays, most of the substations are used in the stratification distributed of protection and control system, a lot of secondary devices placed in the high-voltage switch factory under high voltage equipment, because of these power electronic device operating signal level compared low and insulation weak which consists of ultra large scale integrated circuit, transient electromagnetic field will interfere with the normal operation of sensitive equipment due to the disconnector operating in the gas insulated substation, so that in the electromagnetic signal interference may occur malfunction or damage to the equipment phenomenon, thereby enabling safe operation of the power system is affected. As a result, the transient electromagnetic field problems in gas insulated substation turns into an important factor for ensuring the safe and stable operation of the power system.For the issues raised, EHV 500 kV gas-insulated substation used for the study in this thesis. Firstly, modeling of primary system in GIS for components of each device is studied and summarized, the inner transient circuit model of primary system for the three-phase split GIS is built too, calculated out the very fast transient over-voltage waveform and its spectrum map caused by the disconnector operation in GIS. Secondly, calculates the transient enclosure overvoltage based on the theory of Multi-conductor Transmission Lines. The results shows that the very transient over-voltage transfer to the GIS case, the interference voltage amplitude housing up to 0.848 p.u, appear on the metal casing of the bushing, the frequency range widely distribution, mainly between 3-35 MHz, its high spatial frequency characteristics is very easy to form the electromagnetic interference.Finally, transient electromagnetic field will be calculated in the selected frequency samples based on the method of moment. Transforming TEV waveform from the time domain into the frequency ones, and sampling in frequency domain, then, get the voltage amplitude of the sample frequency as the excitation source imported into the thin line model. Distribution of electric and magnetic fields show that the spatial location is a key factor for transient electromagnetic fields. In the near filed pattern, electric field intensity and magnetic fieldintensity will rapidly attenuates along with the increases of the distance between the source location and the measurement point, the change of the electric field intensity and magnetic field intensity gradient is steep, forming a complex in homogeneous field. At the same time, in the near filed pattern, electric field strength is greater than the intensity of magnetic field on the effects of space transient electromagnetic field. By different frequency electric field intensity calculation results can be seen that frequency has certain effect on electric field intensity, electric field intensity will decline with the increase of the frequency, and the electric field intensity is more serious in the main frequency of VFTO. |
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