Research On The Theory And Simulation Modeling Of Switching Overvoltage Of 10kV Shunt Reactor

With the wide application of vacuum circuit breaker and shunt reactor in the distribution network,the frequent occurrence of equipment insulation breakdown caused by the over-voltage generated when vacuum circuit breaker breaks shunt reactor has become a non-negligible problem. To ensure the safety of electrical equipment and the stable operation of the power grid,and avoid the economic losses caused by frequent accidents,it is necessary to study the process of switching the parallel reactors of the vacuum circuit breaker, find out the essential causes of the accident, and take necessary countermeasures.This article mainly conducts research on the overvoltage generated by the vacuum circuit breaker breaking l0kV parallel reactor from two aspects: theoretical analysis and simulation modeling.Firstly,the related theories of operating overvoltage and intercepting overvoltage are introduced,and the intercepting overvoltage generated by the circuit breaker breaking parallel reactor in l0kV system is studied. Based on the circuit theory, the equivalent circuit models of single-phase and three-phase are established,and the shunt overvoltage of the parallel reactor is calculated.Through sensitivity analysis, it is concluded that the cutoff value of the circuit breaker and the inductance of the reactor are important factors affecting the magnitude of the overcurrent.The influence of the cutoff value of the circuit breaker and the inductance of the reactor on the magnitude of the overvoltage is analyzed.Secondly,the basic structure of the three-core cable and ATP-EMTP software are briefly introduced.In 10kV three-core cable,the waveform of high frequency voltage will change with the change of frequency, so the frequency related JMarti model is selected to model the 10kV three-core cable connecting vacuum circuit breaker and shunt reactor in the substation:the actual cable geometric parameters are converted into the geometric parameters of the simulation model,and the fine multi-layer modeling of the 10kV three-core cable is performed to obtain a more accurate simulation model.Finally,the main equipment parameters and parasitic parameters of the system are fully considered,and the process of breaking the 10kV shunt reactor by the vacuum circuit breaker is simulated by using ATP-EMTP software.The current waveform between the circuit breaker breaks,the voltage waveform on the bus side, the voltage waveform at the parallel reactor and the recovered voltage waveform between the circuit breaker breaks are analyzed.The simulation results show that when the 10kV shunt reactor is interrupted by the vacuum circuit breaker,the overcurrent generated by the interruption causes multiple reignitions in the gap of the fracture,resulting in areignition overvoltage with a high amplitude and frequency,and the reignition overvoltageis less than the cut-off overvoltage; and several theoretically feasible methods to suppress the cut-off over- voltage of shunt reactors are briefly introduced and analyzed.