基于故障电流回路特性的柔性直流架空线路纵联保护

Pilot Protection of Flexible DC Overhead Line Based on Characteristics of Fault Current Loop

接地极是真双极柔性直流输电系统特有、不可或缺的重要组成部分。当线路发生单极接地故障,双极平衡被打破,故障回路有零序电流分量。接地极是零序电流的必经通路,故障电流大且具有方向性。利用本端接地极、故障极和健全极测量端电流满足基尔霍夫电流定理,实现交流侧以及反向故障的正确快速识别;利用接地极电流方向能够实现可靠选极。基于整流侧和逆变侧独立判断的结果控制断路器,不依赖通信。同时,提出利用逆变侧判断结果和通信的重合机制,构成前加速保护方案。所提保护方法实现了线路高阻故障的快速识别,降低了保护定值整定的难度。仿真验证结果表明所提保护方案算法简单、可靠性高,对数据采样率要求低。

The grounding electrode is a unique and indispensable part of the true bipolar flexible DC transmission system.When a single-pole grounding fault occurs on the line,the bipolar balance is broken,and the fault circuit has a zero-sequence current component.The grounding electrode is the necessary path for zero-sequence current,and the fault current is large and directional.The currents of the grounding electrode,fault electrode and sound electrode at this end meet the Kirchhoff current theorem,so as to realize correct and rapid identification of AC-side and reverse fault.Reliable electrode selection can be realized by using the current direction of the grounding electrode.The circuit breaker is controlled based on the results of independent judgment on the rectifier and inverter sides,which is independent of communication.At the same time,a pre-acceleration protection scheme is proposed based on the judgment result of inverter side and the coincidence mechanism of communication.The proposed protection method realizes the rapid identification of high-resistance faults of transmission lines,and reduces the difficulty of protection setting.The simulation results show that the proposed protection scheme has a simple algorithm,high reliability and low requirement for data sampling rate.