基于m-Ucosφ平面识别振荡期间输电线路不对称故障的方法

Identification of Transmission Line Unsymmetrical Fault During Power Swing Based on m-Ucosφ Plane

距离保护作为输电线路的后备保护在电力系统广泛应用,但是系统振荡期间测量阻抗变化会导致距离保护误动作,在系统振荡期间需要闭锁距离保护,而系统振荡期间线路发生不对称故障时需要快速开放距离保护,现有距离保护利用电流不对称度识别振荡期间不对称故障,识别故障电阻的灵敏度低,无法快速开放距离保护。提出了一种综合利用保护安装处电流、电压特征识别振荡期间线路不对称故障方法,利用保护安装处的电压余弦分量反映故障点处的电压,建立了电流不对称度–电压余弦分量平面,从电流和电压两个维度综合反映系统振荡及线路故障特征,在此基础上,构建了系统振荡期间线路不对称故障的识别判据,提高了保护识别振荡期间线路不对称故障的灵敏性,缩短了距离保护开放时间,实时数字仿真系统(real time digital system,RTDS)仿真结果验证了本方法的有效性。

Distance protection,as an important backup protection of transmission lines,is widely used in power systems.During a power swing,the change of measured impedance may lead to mal-operation of distance protection So distance protection must be blocked during a power swing.However,when an asymmetric fault of the transmission lines occurs during a power swing,the distance protection should be switched on quickly.Normally,the current asymmetry degree is used to identify an asymmetric fault of the transmission line during a power swing,whose low sensitivity of fault identification cannot switch on the distance protection quickly.An identification of the transmission line asymmetric fault during a power swing based on the current and voltage characteristics at the relay location is proposed in this paper.The voltage at the fault point is calculated by the voltage cosine component of the relay location.The two-dimensional planes of the current asymmetry degree and the voltage cosine component are established to analyze asymmetric fault characteristics during the power swing.The asymmetric fault identification criterion is proposed.The sensitivity of the distance protection to identify the line asymmetric faults during a power swing is greatly improved and the RTDS(real time digital system) simulation results verify the effectiveness of this method.