Study on Very Fast Transient Electromagnetic Interference Model under GIS Disconnector Operation

In the context of the reverse distribution of power resources and demand in China, gas-insulated substations (GIS) are widely used as power transmission equipment in UHV power transmission projects in my country. When the disconnector in GIS performs the opening and closing operations, multiple arcing will occur between the dynamic and static contacts, resulting in a very fast transient overvoltage (VFTO) with the characteristics of high frequency, high amplitude and fast rise. In addition, it will also cause a very fast transient overcurrent (VFTC), resulting in changes in the transient magnetic fields, which will affect the operation of secondary equipment. Therefore, this paper investigates the formation mechanism of VFTO and VFTC in UHV GIS equipment, the waveform characteristics and the factors affecting the very fast transient process. First, the principle of arc re-ignition caused by disconnector operation in GIS is explained, and the formation mechanism of VFTO and VFTC and their respective transient characteristics are analysed. Based on the one-dimensional transmission line simulation theory, the existing simulation methods and the electromagnetic transient equivalent model of the disconnector in GIS are studied. The basic concepts, differences and applicability of various arcing resistance models for simulating the operation of disconnectors are analysed, and the exponential arcing model is selected for the simulation calculation of the models. The reason for selecting the equivalent model of the corresponding parts in the GIS in the simulation model and the specific parameter calculation process are explained. In this paper, a 252kV standard GIS disconnector operation simulation circuit is first established in PSCAD software, and the waveform data of VFTC and VFTO including amplitude, rise time, time domain and frequency domain characteristics are obtained. The characteristics of frequency distribution, amplitude change, rise time, etc. of voltage and overcurrent are compared with some reference data using actual measurement experiments to verify the one-dimensional transmission line simulation theory used in this paper and the equivalence of GIS components The correctness of the model and the exponential arcing model, and the similarity and accuracy of the waveform of the very fast transient process obtained by simulation and the actual measurement results. After confirming that the simulation theory and the equivalent model are suitable, one of the single-unit single-strip outgoing circuits of an actual 550kV GIS substation is set up, and the factors affecting the phenomenon of very fast transient electromagnetic interference are analyzed and the corresponding suppression method is given.