Research On Ferroresonance Of Power System With PT Hysteresis Effect

In the power system,in order to convert the information of high voltage and high current in the power network into low voltage and low current for meter measurement,measurement and connection of relay protection devices,electromagnetic voltage transformers are usually installed on the bus line to realize this function.However,due to the nonlinear excitation characteristics of electromagnetic voltage transformer itself,it is easy to saturate under the impact of over-voltage or over-current,so that the capacitor distributed in the system and the nonlinear inductance of the electromagnetic voltage transformer match to excitation resonance,resulting in ferromagnetic resonance overvoltage,which causes serious harm to the normal operation of the power system and equipment.Therefore,it is of great significance to further study the establishment of reasonable model of ferroresonance overvoltage,resonance mechanism,influence factors and suppression measures.This paper is based on the theory of electromagnetic dual transformation,by analyzing the topological structure of the windings and core of the single-phase three-winding electromagnetic voltage transformer,the equivalent circuit electromagnetic transient model considering the hysteresis loss,leakage inductance and capacitance of the transformer was established.According to the model,the parameters required for simulation was calculated.According to the structure diagram of the electromagnetic voltage transformer,the average hysteresis loss,stray capacitance and leakage inductance of the core were calculated by the traditional theoretical algorithm and the finite element method.In the electromagnetic transient simulation software ATP-EMTP platform,The simulation network of ferroresonance overvoltage system including the above transformer model was established for simulation.The influence laws of hysteresis loss of transformer,leakage inductance of winding and stray capacitance on resonance overvoltage of the system are analyzed.On this basis,the influence of single-phase grounding and three-phase switching at different time on excitation resonant overvoltage was analyzed based on the topological model which fully considers various parameters.Ferromagnetic resonance elimination strategy is added to the system model,and three harmonic elimination measures of voltage transformer primary neutral point through resistance grounding,open triangle connecting resistance and neutral point through arc suppression coil grounding are simulated and analyzed,and the advantages and disadvantages of various harmonic elimination measures are summarized.