不同类型机械绝缘节快速暂态过电压产生机理

Generation Mechanism of Fast Transient Overvoltage in Different Types of Mechanical Insulation Joints

通过对列车经过第一类和第二类绝缘节的快速暂态过程进行理论分析,建立列车经过2种机械绝缘节的等效暂态模型,研究机械绝缘节快速暂态过电压的产生机理,并推导其计算公式。利用ATP-EMTP电磁暂态仿真软件搭建列车经过2种机械绝缘节的牵引回流等效电路,对快速暂态过电压产生过程进行模拟和仿真计算。结果表明:列车车轮带负载脱离机械绝缘节的瞬间,相当于在绝缘节两端钢轨处施加1个方向相反、大小相等且均等于牵引电流瞬时值的冲击电流,产生的快速暂态过电压与该电流成正比;第一类绝缘节快速暂态过电压幅值等于牵引电流瞬时值与该类绝缘节冲击阻抗的乘积;第二类绝缘节由于与扼流变压器并联,其快速暂态过电压幅值远小于第一类绝缘节,在站场正线及出站方向等牵引电流较大的区段不应设置第一类绝缘节。

Through the theoretical analysis of the fast transient process of the train passing through the first and second types of insulation joints,the equivalent transient model of the train passing through two types of mechanical insulation joints was established.The generation mechanism of the fast transient overvoltage of the mechanical insulation joints was studied and its calculation formula was deduced.ATPEMTP electromagnetic transient simulation software was used to build the equivalent circuit of traction return current of the train passing through two types of mechanical insulation joints,which was used to simulate and calculate the generation process of fast transient overvoltage.Results show that the moment when the train wheel breaks away from the mechanical insulation joint with load is equivalent to applying an impact current to the rail at two ends of the insulation joint.The impact current is opposite in direction,equal in size and equal to the instantaneous value of the traction current,and the fast transient overvoltage generated is proportional to it.The amplitude of the fast transient overvoltage of the first type of insulation joint is equal to the product of the instantaneous value of the traction current and the impulse impedance of this type of insulation joint.Because the second type of insulation joint is in parallel connection with the choke transformer,its fast transient overvoltage amplitude is much less than that of the first type.Therefore,the first type of insulation joint should not be set in the section with large traction current,such as the main line of the station and the departure direction.