福州特高压变电站短路电流分流系数计算与分析

Calculation and Analysis on Short-circuit Current Shunt Coefficient in Fuzhou UHV Substation

变电站内发生短路故障时真正引起危害的是入地故障电流,而不是短路故障电流。分流系数表征了接地网或架空地线对故障电流的分流能力,可用于分析短路电流的分布情况。研究了变电站站内故障时短路电流的分流机制,提出了适用于工程实际的分流系数定义,重点介绍了分流系数的数值计算方法。在此基础上计算了福州特高压变电站的分流系数与短路入地电流,并分析了分流系数的各种影响因素。分析结果表明:地线分流系数随着变电站接地电阻的增大而增大,随着杆塔接地电阻的增大而减小;500 kV侧和1 000 kV侧短路时地线分流系数差别较小;随着变电站接地电阻的增大,最大入地电流减小,接地电压增大。

When a short-circuit fault occurs in a substation,it is the current diffusing into ground that actually causes the safety trouble instead of the fault current.Shunt coefficient characterizes the shunt ability of grounding grid or overhead ground wires to fault current,so it can be used to analyze the distribution of short-circuit current.The shunt mechanism of short-circuit current is studied when a fault occurs in substation,a definition of shunt coefficient that is more suitable for engineering practice is proposed,and the numerical computation method of shunt coefficient is introduced.On this basis,the shunt coefficient and current diffusing into ground of Fuzhou 1 000 kV substation are calculated,and various factors affecting the shunt coefficient are analyzed.The results show that shunt coefficient of ground wire increases with the increase of substation grounding resistance and decreases with the increase of tower grounding resistance,the differences of shunt coefficient of ground wires is tiny when short-circuit fault occurs in 500 kV side and 1 000 kV side.With the increase of substation grounding resistance,the current diffusing into ground decreases and the ground potential rise increases.