一种基于极性判别的环状直流配电网线路后备保护方法

Study on the Back-up Protection Method for Loop DC Distribution Lines Based on Polarity Discrimination

应用于直流线路的纵联差动保护方法,由于其可靠性高,被广泛应用在我国输配电系统中,并取得了良好的运行效果,然而,随着分布式电源在配电网中的快速发展,导致在发生高阻故障时,其门槛值不易设定,保护动作可靠性差,并且传统配电网保护难以适用于环状直流配电系统。该文提出一种基于电流突变量斜率方向的纵联后备保护方法。首先,分析直流配电线路区内、外故障时两端电流突变量方向的特征。然后,提出将斜率方向引入电流突变量方向特征检测中,利用低频带故障电流信号的极性关系,实现能准确动作于直流配电线路的后备保护方法。最后在Matlab/Simulink中构建仿真模型,仿真结果表明,该保护方法有较强的抗过渡电阻及抗干扰能力,能准确识别故障所在范围,可以在一定程度上提高后备保护可靠性。

Longitudinal differential protection methods applied to DC lines are widely used in transmission and distribution systems in our country because of their high reliability and good operation results have been obtained. However,with the rapid development of distributed generation in the distribution network,the threshold value is not easy to be set when high-impedance fault occurs,and the reliability of the protection action is poor. Traditional protection method for distribution network is not suitable for the ring DC distribution system. In this paper,a method of longitudinal protection based on the slope of sudden current change is proposed. First of all,the direction of the sudden current change at both ends of DC distribution line are analyzed. Then,it is proposed to introduce the slope direction into the direction detection of the sudden current change. Using the polarity relationship of the fault current signal in the lowfrequency band,a backup protection method capable of accurately operating for the DC distribution line is realized. Finally,a simulation model is built in MATLAB/SIMULINK. Simulation results showthat this method has strong capability free from jamming and the affection of transition resistance,and to accurately identify the fault range and to improve the backup protection reliability to a certain extent.