| Disconnector operations in gas insulated substation (GIS) may generate VFTO, which is characterized by its high peak value, short rise time, and high frequencies. This over-voltage may cause high electric stress to the insulation in GIS and the adjacent apparatuses. Some experts think that the model of the arc plays an important part in the simulation of the VFTO. As a result, the study of the arc model of the disconnector is useful.The existing results of the arc model indicate that the resistance of the arc has a great relationship with the current. In this paper, the author designed VFTO measuring system and VFTC measuring system for the252kV GIS experimental circuit to get accurate VFTO and VFTC which generate when the disconnector is operated. In order to get the gap distance between the contact terminals of the disconnector, a distance measuring system is also designed. The VFTO measuring system is based on the theory of capacitive voltage divider, which the flat plate films capacity is used on lower voltage divider, and the distributed capacity between GIS conducting rod and lower-voltage electrode is used on higher voltage side. The VFTC measuring system consists of Pearson coil and fiber transmission system, and it can measure the VFTC even the electric potential of the rod is high. Distance measuring system consists of a PSD, a laser source and a plano-convex lens. After testing, the three measuring system all satisfy the requirements. The lower cut-off frequency of the VFTO measuring system is smaller than20Hz, and the higher cut-off frequency is larger than80MHz. The bandwidth of the VFTC measuring system is70MHz. The distance measuring system can measure the entire gap between the contact terminals.Experimental results show that the rise time of VFTO is about20ns, and the main vibration frequency is5MHz and40MHz. The rise time of the VFTC is about5ns, and the main vibration frequency is about25MHz and70MHz. |
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