| Gas insulated substation (GIS) can produce many kinds of transient overvoltage, and thevery fast transient overvoltage (VFTO) caused by reigniting of arc is one of the transientovervoltage. The high amplitude features of VFTO greatly threatens the insulation of the GIS,and also can cause damage to insulation of electrical equipment connected to GIS, so theproblem must be given enough attention in EHV and UHV transmission system. In this paper,the VFTO of GIS is studied through computer simulation. The simulation results and the dataare beneficial to the prevention and inhibition of VFTO, and also have important referencemeaning to the insulation design of GIS’s electrical equipment.The accurate structures of the GIS equipment model have a great influence to theaccuracy of the simulation results in the simulation study of VFTO, and the selection ofisolating switch arc model is crucial. And arc model currently used mostly have limitations,also does not have uniform standard, so arc model is the focus in the research of VFTO. Firstof all, this paper analyzes the various characteristics of VFTO and the arc model commonlyused, combined with ATP-EMTP and a1000kV gas substation. On this basis, arc resistancemodel considering arc inductance characteristic、virtual inductance arc model and real-timedynamic arc model are put forward, which are three new arc model.The detailed analysis andcalculation of key equipment VFTO in substation are done, by comparison with other arcmodel.The article then studies the influence of the residual charge, entrance capacitance andthe branch length on VFTO. Finally several inhibition method of VFTO are analyzed, such as500Ω single-stage closing resistor、500Ω three-level closing resistor and ferrite beads. Theconclusion is as follows：(1) The three kinds of arc model put forward can well describe the process of the arc.Time-varying resistance ignores the inductance characteristic, and arc resistance modelconsidering arc inductance characteristic can make up the shortfall and model structure issimple, so it is suitable for the study of VFTO under the condition of ignoring the arc modelfactor. Dynamic inductance is difficult to set up and affect the system stability in arcresistance model considering arc inductance characteristic, but virtual inductance arc modelcan solve the problem. It is suitable for use considering inductance characteristics of arc.Real-time dynamic arc model can better solve the problem of time node criterion than segmental arc model, and it takes into account the non-ideal sections of arc caused byrecovery voltage and other factors, so it has a very wide scope of application.(2) VFTO amplitude increases along with the residual charge; The VFTO of Transformerhas no a a regular increase with the increase of transformer entrance capacitance under theinfluence of system structure、operation mode、system parameters and other factors; Theimpact of branch’s length has no obvious regularity, and the influence of bus bar lengthchange is higher than the branch length change.The impact of main branch length is higherthan branch length’s.(3)500Ω three-level closing resistor whose sum is500has no more advantagescompared with500Ω single-stage closing resistor, instead it can make the structure of GISmore complicated, so not recommended. Ferrite beads can suppress VFTO well, which has abetter overall performance than the closing resistor. |
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