Calculation And Analysis Of Very Fast Transient Overvoltage In Gis Based On Accurate Arc Model

In the paper, a special operating overvoltage--Very Fast Transient Overvoltage (VFTO) has been analyzed, and the amplitude, frequency and steepness of wave front of overvoltage on the important element has been calculated.In order to accurately calculate and analyze VFTO, it is extremely essential to build accurate arc model. Many arc models exist in the electrical power system, but they all have their own limitations. A new arc model has been put forward, that is Cassie-Mayr arc model.In the model, the arc process has been divided into three stages:prebreakdown, arcing and extinguishing.In different stages, arc resistance present different change rules. Moreover based on the typical GIS circuit and utilized the ATP/EMTP program, the variation of VFTO is studied with the new arc model and traditional arc models. It is indicated from VFTO amplitude and steepness that the new arc model has better precision. Then calculating processes with the improved Euler algorithm has been given in the paper, including the equivalent of components, obtaining parameters, step length selection and writing and solving the differential equation of column.Thirdly, starting from a practical problem happening in the220kV GIS of PingBan hydropower station, based on the parameters provided by operating crew, the VFTO of key position in the GIS has been calculated. Meanwhile, three influencing factorss are analyzed. In the last part, the thesis gets the conclusion:residual charge voltage and DS closing resistor has the greatest influence on VFTO, while the influence of transformer entrance capacitance is not significant. Based on research results above, three influencing factorss are analyzed and some methods suppressing overvoltage are put forward.