Interrupting Performance of Capacitive Current By Disconnecting Switch for Gas Insulated Switchgear

Development of 1‐GHz GIS surge sensor

“…5(a). Regarding this circuit , the potential division r a tio fo r the upper limit freq uency Ph can be given by the following : ph=CI/2(CI +C2) (3) Als o , the potential freq uen cy following equatio n a pplies to the division ratio fo r th e lower limit (4) where C is the capaci t y possessed by the cone-shaped coaxial structure; a nd C k is the capacity possessed by coaxial cable .…”

“…Due to the excellent insulation characteristics of SF~ gas, gas-insulated switchgear (GIS) is used widely at high-voltage substations. It is well known that fast transient overvo1tages (FTO) with risetimes of several nanoseconds are generated as a result of operation of the disconnector installed in GIS [1][2][3][4][5].…”

“…At the same time, it has been noted that there is a possibility that the levels of FTO exceed 3.0 pu (1 pu is the crest value of operating voltage) [2]. Further, as problems involving FTO, not only is the phenomenon of flashover to ground from interpo1e arcs of operating disconnectors [3,4] discussed, but also the influences on transformers, bushings, and other devices [5]. In recent years.…”

Spark model for 1100kV GIS disconnecting switch

“…Due to the relatively slow operating speed and the poor performance of arc extinction, at every operation of the disconnect switch, a large number of repetitive discharges between the disconnect switch contacts occurs during at least 100 ms [1]. Pointed out as problems associated with VFTO are not only the phenomenon of "flashover to ground" from the disconnecting switch contacts [2] [3], but also influences on other components such as transformers and bushings [4]. Other problems such as erroneous operation and failure of electronic control circuits connected to GIS units are subjected to electromagnetic interference by VFTO.…”

Estimation of Restriking Transient Overvoltage on Disconnecting Switch for GIS

“…On SF6-gas disconnecting switches installed at the GIS's, recently it has become known that a phenomenon of "flashover to ground' from the DS contacts is occasionally caused by the said high-frequency surge voltage [ 1,2]. When conducting studies on insulation coordination at GIS's, it is believed to be necessary to take into account restriking surges associated with the use of DS's.…”