Ground Fault by Restriking Surge of SF₆ Gas-Insulated Disconnecting Switch and Its Synthetic Tests

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.…”

Suppression of Fast Transient Overvoltage during Gas Disconnector Switching in GIS

“…These strikings generate fast transient overvoltages with a high frequency between 100 kHz and 10 MHz. These overvoltages may cause a dielectric breakdown in the GIS [ l], [2], [3], a transient potential rise of the GIS sheath, and a transient overvoltage in the low voltage control circuit, all deleterious effects.…”

“…(1) (2) Here, Vo is usually I.Opu and C is generally the total capacitance of the load side. overvoltage at Q rose as an approximate exponential function as shown in Fig.…”

“…Its time to crest of less than 0.1 s and its time to the half value of 5 s were less than those times for standard lightning impulse voltage. The energy absorption of 4-8kJ per one severest striking was calculated from formula (2). Assuming ten severest strikings, 1OOkJ per one operation of the DS was given with about a 10% safety margin.…”