10kV线路缺相对系统及配变影响分析

Analysis of the Influence to System and Distribution Effect of 10kV Lines Missing phase

为保障人身安全,城市供电区域的10kV系统通常采用小电阻直接地方式。当10kV小电阻接地系统发生典型的单相接地故障,时由于零序回路阻抗较小,系统产生的零序电流较大,保护装置能灵敏判断故障故障电流并快速切除线路。但当发生线路断线且只有负荷侧接地时,由于系统的零序阻抗变大,产生的故障电气量较小,保护的灵敏度不足而不动作,使线路在缺相状态下运行,故障接地点会产生相电压一半的电压,存在人身触电风险,同时故障点后侧的配变处于缺相运行状态,影响居民和工业正常用电。为深入分析这类故障发生时系统各种参量的变化情况,找到具有针对应的解决办法,文章根据云浮地区的发生两起10kV线路缺相故障进行分析对比,采用等值电路方法计算故障时系统的零序电流以及电压偏移量,把计算值与相关测量系统的数据作对比,找出故障原因并提出改进措施。

In order to protect personal safety,the IOkV system in the urban power supply area usually adopts a small resistance direct method.When a typical single-phase ground fault occurs in a 10 kV small-resistance grounding system,the zero-sequence current generated by the system is large due to the small zero-sequence loop impedance,and the protection device can sensitively determine the fault fault current and quickly cut off the line.However,when the line breaks and only the load side is grounded,the faulty electrical quantity is small due to the large zero-sequence impedance of the system,and the sensitivity of the protection is insufficient to operate,so that the line runs in the phase-deficient state,and the fault ground point will generate half the phase voltage,and there is a risk of electric shock in life.At the same time,the distribution of the rear side of the fault point is in a phase-deficient operation state,which affects the normal use of electricity by residents and industry.In order to deeply analyze the changes of various parameters of the system when such faults occur,and find a solution to the problem,this paper analyzes and compares the two phase failures of lOkV lines in Yunfu area,and equivalent circuit method is used to calculate the zero-sequence current and voltage offset of the system at the time of the fault.The zero sequence current and the voltage offset are compared with the data of the relevant measurement system to find out the cause of the failure and propose improvement measures.