Study On GIS Enclosure Circulating Currents And Transient Grounding Potential Rise

Enclosed gas-insulated substations (GIS) have some significant advantages, such as compact, good anti-fouling ability, easy maintenance, conducive to environmental protection. As a result, they have been widely used in power systems. But precisely because of its compact structure, when the switchgear, such as the isolating switch, circuit breakers or other switching equipment, can easily produce very fast transient over-voltage which the oscillation frequency up to tens or even hundreds of megabytes. Through the study we found that, the production of VFTO can often lead to GIS enclosure circulating currents and transient ground potential rise, causing heavy losses.Calculation of GIS bus parameters were analyzed in the paper, and the impedance formula, which of its accuracy was verified by finite element method, was derived too. And the data of impedance, which get with Ansoft maxmell 2D soft, consistent with result of the formula. The basic circuit of the GIS was studied by the power system transient analysis software PSCAD/EMTDC in this paper. The impact of the lines VFTO were analyzed, and made some prevention and resolution measures of VFTO.The model of GIS enclosure was built in PSCAD/EMTDC software, which is under consideration of GIS grounding devices in the effect of grounding the distribution parameters, was considered. The model simulated in the situation of that the operation of the isolation switch, circuit breaker. The voltage wave of VFTO was moved into GIS circulation model directly to analyze the circulation waveform, and then comprise it with the experimental data. The approximate analytical method was used in the research of transient ground potential rise, and establish GIS enclosure potential model in PSCAD/EMTDC software. The TGPR date, which is based the simulation in PSCAD/EMTDC software, consistent with the experimental data, and the error within the allowable range, which proves the correctness of the model. What's more, we found some laws of transient ground potential rise. Effect of the grounding location for transient ground potential rise was considered, too. And we got that the closer of the grounding, the better of the effect for transient ground potential rise. What's more, the effect of capacitor, which is installated in insulated flanges, for transient ground potential rise, was consided in the paper. Through the comparation of MOA installed in flange in two ways, we know some feature of transient ground potential rise.We take 500kV GIS system in a domestic hydropower station for analysis, and do the research of VFTO voltage and do with the over-voltage statistics in critical node in GIS in PSCAD/EMTDC software, and then get the calculate voltage used in insulation. Then do the measures of circulating current in GIS system, and comprise it with the experimental data. We also do the research of the transient ground potential rise in GIS system, and get the TGPR voltage waveform in the established model, which of the results are consistent with the experimental data that can verify correctness and validity of the model.