Test and Modeling Study of Oil-SF6 Bushing under VFFO

Abstract

Oil-SF6 bushing is the one of the most important equipment connecting GIS (Gas Insulated Switchgear) and transformer, and the simulation model of Oil-SF6 bushing is the key for the evaluation of VFFO level of GIS substation or in pumped-storage power station. For this purpose, many VFFO tests are carried out on the full operating condition testing platform, and measured waveforms of overvoltage on the UHV oil-SF6 bushing are available. Secondly, the capacitance of UHV oil-SF6 bushing is analyzed and calculated, and three models of bushing—simplified transmission line model, lumped model and multiple equivalent layers model, are put forward. Compared with measurement acquired from the test and results from simulation, the model of transmission line combined with lumped capacitance is recommended for the evaluation of VFFO, with which the waveform of overvoltage at the entrance of transformer can be further calculated.