短路故障下低压开关柜电磁热耦合瞬态温升变化

Electromagnetic thermal coupling transient temperature rise of low voltage switchgear under short circuit fault

低压开关柜内部包含多个开关元件,结构复杂,存在多个电接触部位,短路故障会导致开关柜内部温度增高,若内部部件发生接触不良会加剧温升,降低低压开关柜的运行可靠性,严重情况会导致该处发生熔断、绝缘损坏和拉弧短路等故障。以一起LKM0201开关柜短路跳闸事故为研究对象,分析该故障原因,建立LKM0201开关柜仿真模型,应用有限元分析软件ANSYS Workbench的Maxwell模块和Transient Thermal模块进行电磁热耦合瞬态仿真分析,研究短路故障对开关柜内部运行的影响,分析故障处在接触良好和接触不良2种情况下内部的温升差异,得出开关柜内部各部件的瞬态温升变化,并将仿真结果与实际故障对比。研究表明:当开关柜发生短路故障时,内部连接处发生接触不良的情况下,开关柜内部接触电阻增大、瞬态损耗增加。短路电路流经时开关柜内部温度升高,接触不良处温升更加剧烈,该温度将高于绝缘材料耐受温度并引起材料变形甚至融化,最终引起绝缘损坏,发生拉弧短路,温升过高可能会出现熔焊甚至熔断现象。仿真结果与事故照片具有较好的一致性,同时该方法具有较好的通用性。

The low-voltage switchgear contains multiple switching elements with complex structure and multiple electrical contact parts.Short circuit fault will increase the internal temperature of the switchgear.If the internal components are poor in contact,the temperature be rising dramatically rise with the operation reliability reduced of the low-voltage switchgear,which will even lead to fusing,insulation damage,arcing short circuit and other faults.Taking a short-circuit tripping accident of LKM0201 switchgear as the research object,this paper analyzes the cause of the fault,establishes the simulation model of LKM0201 switchgear,carries out electromagnetic thermal coupling transient simulation analysis by using the Maxwell module and Transient Thermal module of ANSYS Workbench,and studies the influence of short-circuit fault on the internal operation of the switchgear.The internal temperature rise difference between good contact and poor contact is examined,the transient temperature rise changes of various components in the switchgear are identified,and the simulation results are compared with the actual faults.The results show that:when the short circuit fault occurs in the switch cabinet,the contact resistance inside the switch cabinet increases and the transient loss increases;when the short-circuit circuit flows through the switch cabinet,the internal temperature increases,and the temperature rise is more severe at the bad contact.The temperature will be higher than the insulation material tolerance temperature and cause material deformation and even melting,and eventually cause insulation damage and arc short circuit.A high temperature rise may result in fusion welding and even fuse.The simulation results are consistent with the accident photos,and the method has a strong versatility.