农村10kV中性点不接地系统单相接地选线的研究

农村10kV配电网接地方式大多数采用中性点不接地方式。该接地模式发生单相接地故障时,由于故障电流较小,找出和排除故障一直以来没有得到很好的解决。中性点不接地系统单相接地故障选线理论已经比较成熟,但是选线装置在实际应用中效果不佳。主要原因是前相通道中信号检测、采样、转换等电路环节存在不可避免的误差。基于MATLAB的PSB对农村10kV中性点不接地系统进行了数字仿真,分析了单相接地故障特征,开发了选线装置。该装置的特点是前向通道电路环节精简,误差小。在实验室模拟系统运行中,选线效果显著。

A Single Phase to Ground Fault in Rural 10kV Power Ungrounded System

The neutral point of rural 10kV power system is usually not conected to ground.When single-phase to ground fault takes place,it is hard to find the fault feeder,since the fault current is small.The theory to find and solve single-phase to ground fault is known,but the earthed relaying devices do not work well in practice.The main reason is the inevitable error caused by forward channel such as detection circuit,sampling circuit and conversion circuit.Digital simulation of rural 10kV power ungrounded system was made based on MATLAB' PSB,and the character of single phase to ground fault was analyzed with this digital simulation.A kind of earthed relaying device was developed based on the analytic character.The earthed relaying device had characteristics of small circuit of forward channel and less error of forward channel.The earthed relaying device could find the fault feeder successfully in the analogue system in latoratory.