A novel pilot directional protection scheme for HVDC transmission line based on specific frequency current
A novel pilot directional protection scheme for HVDC transmission line based on specific frequency current
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DOI：
10.1109/powercon.2014.6993931
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发表时间：
2014-12
期刊：
影响因子：
--
通讯作者：
Jian Liu;C. Fan;N. Tai
中科院分区：
文献类型：
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作者：
Jian Liu;C. Fan;N. Tai
高压直流输电线路在远距离输电中发挥着重要作用，但由于地形复杂、气候恶劣等原因，直流线路故障频繁发生，是造成高压直流输电停运的主要原因。高压直流输电线路接地故障检测采用行波保护和电压导数原理作为主保护，差动保护作为后备保护。然而，行波法和电压导数法仍存在不足，电流差动保护动作延时较大。因此，高可靠性的保护对保证高压直流输电线路的安全运行是非常重要和必要的。通过分析直流线路端部特定频率电流的方向特性，提出了一种新的高压直流输电线路纵联保护原理。通过对直流滤波器的频谱分析，采用比频电流，分析了线路内部故障和线路外部故障时比频电流的方向，发现线路内部故障时，直流线路两端检测到的比频电流方向相同，而线路外部故障时，直流线路两端检测到的比频电流方向相反。因此，可以利用特定频率电流的方向差异来识别外部故障和内部故障。通过对行波保护中两个电压导数判据的重新设置，提出了一种改进的高压直流输电线路后备保护方案。仿真结果表明，该保护方案是有效可行的，并具有区分高过渡电阻故障的能力。
HVDC lines play an important role in transmission power over long distance, while faults frequently occur on DC lines due to complex terrain and terrible weather conditions, which is a major cause of HVDC outages. Traveling-wave-based protection and voltage derivate theory are used as the primary protection for HVDC transmission lines to detect a ground fault, and differential protection is employed as backup protection. However, traveling-wave-based methods and voltage derivate theory still have shortcomings and current differential protection operates with long time delay. Thus, protection with high reliability is very important and necessary to ensure the security of HVDC transmission lines. By analyzing the direction characteristics of specific frequency current at DC line ends, a novel pilot protection principle for HVDC transmission lines is proposed. The specific frequency current is adopted through spectrum analysis of DC-filter and their directions are analyzed during internal and external fault, and it is found that the directions of specific current detected at DC line ends are the same during internal fault, while their directions are opposite during fault outside of DC lines. Therefore, the direction difference of specific frequency current can be used to identify external fault from internal fault. An improved backup protection scheme for HVDC transmission line is also proposed by resetting two voltage derivative criterions in traveling-wave-based protection. Simulation results show that the proposed protection scheme is valid and feasible, and is of capability to distinguish fault with high transition resistance.