Calculation And Characteristic Analysis Of VFTO Of Xilingol 500kV Substation

The continuous development of economy and society has put forward higher requirements to the power system. Gas insulated substation(GIS) covers an area of small, insulation and good performance, which is suitable for urban substation construction and ultra-high voltage substation construction. GIS has been widely used in electric power system. However, the very fast transient overvoltage(VFTO) will have a greater harm to the GIS equipment.Taking the 500 kV Xilingol GIS substation as the study object, the principle of VFTO producing reason, inhibition method and classification were described in this paper. Based upon these, VFTO simulation model for the main electrical equipment of GIS is proposed. What’s more, on the base of the main wiring diagram of Xilingol GIS substation, the simulation circuit was built through the EMTP simulation software. The VFTO under 6 usual operation modes of Xilingol substation were calculated. The calculation results under different operation modes were show that operation mode has an important impact on the VFTO: the maximum amplitude of VFTO under different operation modes is 2.19 p.u., which is meet the requirement of safety rules; the farther for the disconnector in operation to the main transformer, the lower amplitude VFTO for the main transformer will bear; when the disconnector in operation is the main transformer’s disconnector, the largest amplitude of the VFTO for the main transformer will bear, which is 2.15 p.u.. Since the Xilingol substation laying this long cable, this paper studies the effects of the cable to the amplitude of VFTO, the study results are as follows: the wave impedance of the cable has weaker influence on VFTO amplitude; the amplitude of VFTO decreases with the increase of the length of the cable, and when the cable length is 80~100m, it will obtain both VFTO inhibition performance and economic. Finally, this paper analyzes the impact of the parallel resistance of the disconnector to the amplitude of VFTO. The results show that the parallel resistance of the disconnector can effectively inhibit the amplitude of VFTO. When the parallel resistance is 500?, the inhibition effect is much better. The mainly study and simulation calculation data in this paper is an example for 500 kV GIS Xilingol substation, and the results of the study will have important guiding significance to the design of GIS substation and VFTO amplitude inhibition.