Analysis Of Ferroresonance In 550kV GIS Electromagnetic Potential Transformer

In recent years,with huge power grid reconstruction and expansion projects throughout the country,its structure has changed greatly.The ferroresonance phenomenon occurs frequently due to the complexity of the grid structure.To ensure the reliability and stability of transmission equipment and network operation,the analysis is particularly important.According to it,this paper mainly studies the ferroresonance produced by electromagnetic potential transformer(PT)and capacitor elements in high voltage system,and obtains the corresponding protective measures and methods.Firstly,the mechanism and the type of ferroresonance are described in detail.In this paper,the power frequency excitation characteristic is used,and the fundamental resonance criterion is obtained by using the power frequency excitation characteristic of nonlinear inductance combined with the volt-ampere characteristic of Davinan power source.The model of transmission line and each electrical equipment model are introduced.Choose suitable PT model and line distributed model as the mathematical model of distribution line.After that,according to the parameters of high voltage substation,the typical bus charging,line switching and system overhaul are adopted as the calculation conditions,and the demage produced by substation are calculated by numerical simulation method.According to the severity of the harm and the actual situation,the corresponding harmonic elimination measures are put forward.Finally,the harmonic elimination scheme is designed,the demage generated are calculated,the harmonic elimination scheme is checked,and the harmonic elimination scheme is determined to ensure the safe operation of the substation.The feasibility is verified and the change of line operation mode on the over-voltage of ferroresonance is analyzed.The suppression effect of different harmonic elimination measures on the system's overvoltage is analyzed.In order to study the harmonic elimination effect,14 working conditions,such as cut-off bus and cut-off short lead line,were simulated respectively.