变电站内短路情况下架空地线分流系数的图论计算方法

A Computing Method Based Graph Theory for Shunt Coefficient of Overhead Ground Wire Under Grounding Fault Occurred Within Substation

架空地线分流系数是确定变电站接地电阻目标值的基础数据,提出了基于图论的多电源供电变电站站内接地短路时架空地线分流系数的计算方法。通过分析变电站内短路时影响架空地线分流的因素,给出了电路模型,用基于图论方法的戴维宁、诺顿等效原理和节点电压法推导出了计算架空地线分流系数的公式。与引用的一个算例进行了数据对比,证明了等值电路模型计算方法的正确性。通过计算实例反映出了架空地线分流系数随故障变电站内接地电阻的增大而增大,随线路杆塔接地电阻的增大而减小,线路前15基左右的架空地线–杆塔系统对架空地线分流系数起决定性影响。

Shunt coefficient of overhead ground wire is a fimdamental data to determine the target value of grounding resistance within substation. A method based graph theory to calculated the shunt coefficient of overhead ground wire under single-phase ground fault occurred within substation with multi power sources is proposed. By means of analyzing the factors impacting the shunt of overhead ground wire when short-circuit fault occurs within substation, a circuit model is given and on the basis of graph theory, Thevenin＇s theorem, Norton＇s equivalence principle and nodal method of analysis a formula of calculating shunt coefficient of overhead ground wire is derived. Taking a quoted calculation example for instance, comparison of the data calculated by the proposed method with its original calculation results shows that the proposed calculation method based on equivalent circuit model is correct. Calculation results of an actual example show that the shunt coefficient of overhead ground wire increases with the increase of grounding resistance value within faulty substation and decreases with the increase of grounding resistance value of transmission tower; the system consisting of the first 15 towers and overhead ground wire plays decisive role to shunt coefficient of overhead ground wire.