Study On Current Limiting Characteristics Of Gas Arc In Plates

With the development of industrialization and intellectualization in our country,the demand for electricity in various industries is constantly increasing,and the capacity of power system is also increasing and expanding.The short-circuit current level of power system keeps rising because of the increase of power load density in some areas,even exceeding the breaking level of circuit breakers on the line.Installing fault current limiter is an effective measure to limit short-circuit current.When the breaker is switched off,arc will be generated between contacts and arc voltage can be used to drive current transfer.In this paper,the methods and influencing factors of rapidly increasing air arc voltage in switches were numerically calculated and analyzed.Coupling the fast lifting arc voltage with the fault current transfer,the fault current could be transferred and limited before the zero-crossing point.The influence of arc voltage lifting on transfer current limiting process was analyzed.Based on the theory of magnetohydrodynamics(MHD),a mathematical model for arc simulation of gas-blown arc chamber was established in this paper.Lorentz force was used as the source term of momentum conservation equation and Joule heat and radiation loss were used as the source term of energy conservation equation to realize multi-field coupling between hydrodynamics and electromagnetic field.Compared with the common research on magnetic field driving arc into ferromagnetic plates and being cut into several short arcs,the arc was driven by air flow at the intake of the arc chamber in this paper and the insulating plate was used to elongate and cool the air arc to increase voltage.Based on the commercial software FLUENT,the numerical calculation of multi-physical field coupling in gas-blown arc chamber was carried out.The movement of steady-state arc as initial condition and the process of arc voltage lifting under the action of airflow field were simulated.The distribution of physical field in arc chamber was analyzed which laid a foundation for the study of the influencing factors of arc voltage lifting.The movement of arc driven by airflow field and the variation of arc voltage during contact opening were simulated and analyzed.In order to obtain the maximum arc voltage in as short a time as possible,the effects of different factors on arc motion and arc voltage variation including plate material,plate spacing and air blowing pressure,plates shape,plate arrangement,outlet position and size,and inlet current were compared and analyzed.Finally,a joint simulation method based on FLUENT and PSCAD was designed.The transient analysis of short-circuit fault were combined with the arc development process after switching operation to simulate the transfer and limitation of short-circuit current.The effect of current limiting when the current limiter was put into operation at different time was analyzed.The fault current can be transferred before the zero-crossing point by using the high arc voltage with fast lifting.The influence of the inlet pressure on the transfer current limiting time was simulated and analyzed.The research on arc motion,arc voltage lifting and transfer current limiting in this paper will provide some guidance for the application of arc voltage lifting and current transfer in switchgear field.