一种基于虚拟电流制动量的电流差动保护

A transmission line current differential protection based on virtual brake current

为了减小负荷电流增加制动量对电流差动保护灵敏度的影响,提出了一种基于虚拟电流制动量的电流差动保护。首先比较线路两侧电流大小,利用两侧电流幅值比与相位关系构造虚拟电流,虚拟电流可以根据线路两侧电流幅值关系自适应调整制动量大小。与利用线路两侧电流相位差的制动量相比:区内故障时,虚拟电流制动量小于电流相位差制动量,提高了电流差动保护灵敏度;区外故障时,虚拟电流制动量等于电流相位差制动量,电流差动保护的可靠性不降低。同时分析了弱馈线路、串补线路电流反相两种情况下虚拟制动电流的适应性。利用RTDS建立仿真模型验证保护的动作性能。仿真结果表明,虚拟电流制动量可以有效提高电流差动保护的灵敏度和可靠性,同时具有良好的适应性。

In order to reduce the influence of load current on the sensitivity of current differential protection, a current differential protection based on virtual brake current is proposed. Comparing current sizes of transmission line firstly, then amplitude ratio and phase relationship of both side currents are used to construct the virtual current. The virtual current can adjust the braking size according to the current amplitude relationship on both sides of the line. Comparing to brake current using phase differences of line both side currents, virtual brake current is smaller than phase differences brake current for internal faults and it improves the sensitivity of zero current differential protection. Virtual brake current is equal to phase differences brake current for external faults and it doesn＇t reduce the reliability of zero current differential protection, its adaptation is analyzed for weak feeder line and current inverse for line with series compensation device. RTDS simulation results show that virtual braking current can improve the sensitivity and reliability of the current differential protection effectively. Its adaptability is good.