Research On Modelling Of GIS And Simulation Of Very Fast Transient Overvoltage

During opening/closing operation of disconnector in GIS, multiple repeated breakdown would reveal for many times. While, repeated breakdown is determined by initial power frequency phase and breakdown characteristics of the contact gap. The total time of repeated breakdown progress is on the level of milliseconds, while the single breakdown is on the level of microseconds. Since the dispersion of breakdown voltage of the contact gap, the randomness of initial power frequency phase and the different simulation timesteps are always ignored, the traditional repeated breakdown model can’t achieve the correct waveforms and the statistical properties of very fast transient over-voltage (VFTO)/very fast transient current (VFTC)Therefore, a 252kV GIS platform for VFTO investigation has been built, and hundreds of opening/closing operations of disconnector are carried. The typical waveforms of voltage and current are recorded, and the breakdown characteristics of the contact gap are worked out. Based on the equivalent circuits of GIS components and the dynamic arc resistance model, the stable and transient simulation circuits are built. On the basis of above mentioned characteristics, a multiple repeated breakdown model for disconnector has been built which combine the stable breakdown time with the transient arcing progress. The simulation method for whole operation of disconnector is proposed by using the interaction of MATLAB and ATP with variable timesteps. Meanwhile, random simulations of the initial power frequency phase and the breakdown voltage of the contact gap are realized by using Monte Carlo method. The multiple repeated breakdown model and the whole progress simulation method is used to calculate VFTO of the 252kV circuit, and the results are in almost agreement with the experimental ones. The waveforms of VFTO and VFTC and their statics characteristics in the test circuit to operate disconnector in 252kV GIS were computed. The accuracy of the simulation model is confirmed by the test results The probability density functions of the character parameters such as the breakdown number, breakdown voltage, rise time, maximum value are achieved with the smoothing kernel density estimation method.Finally, the method of the whole progress VFTO simulation established above is applied to UHV GIS circuit. The simulation results about the whole progress VFTO waveform are in almost agreement with the experimental ones which means the simulation method is also effective to the other GIS. Then establishes a simulation model about 550kV gas insulated switchgear (GIS) of Hongping pumped storage power station calculates and analyzes the very fast transient overvoltage (VFTO) when switching the disconnector under several operation modes.