558 / 2017-05-14 15:45:17

Study on the VFTO in 800kV GIS based on Mayr-Schwarz Arc Model

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Very fast transient overvoltage (VFTO), which is generally occurred in SF6 Gas Insulated Switchgears (GIS).VFTO is a kind of type operational overvoltage. It has the characteristics of steep front and high amplitude. The overvoltage caused by the operation of the disconnector has been studied by many scholars. When the disconnector closing and switching off charging current of bus, the high frequency oscillation will occurred because of the repeated arc breakdown and extinguishing of the contact. Considering the residual charge and arc resistance are the important factors of VFTO. It is very important to establish the arc model in the process of simulating.
Numeric simulation and experiment comparison were used of determining the component parameter of GIS which have also provided a dynamic circuit model. The physical process of arc re-ignition is studied based on the theory of arc energy conservation in this paper. Mayr-Schwarz arc equation is applied to the establishment of arc resistance model. From the results above analysis, a new transient circuit model which simulated disconnector closing and switching off charging current of bus on 800kV gas insulated switchgears is established in EMTP-ATP.
The results show that comparing with the traditional arc model, Mayr-Schwarz arc model can better reflect the physical change of arc re-ignition, especially the process of arc extinguishing. At the same time, the amplitudes of VFTO on different point are not the same. waves on disconnector are obviously higher than it on transformer. The frequency compositions of VFTO which are obtained from Discrete Fourier Transformation (DFT) also have significant difference.