利用滤波器支路电流的高压直流输电线路全线速动保护

A Whole-line Quick-action Protection Principle for HVDC Transmission Lines Using One-end Current of DC-filters

为提高直流输电线路单端量保护的可靠性和灵敏度,提出一种利用单端直流滤波器支路电流的输电线路全线速动保护方法。对系统非故障运行时滤波器支路谐振频率电流进行了理论分析和仿真验证;对区内、外故障直流滤波环节阻抗特性及滤波器支路电流进行了研究。分析研究发现,在区内、外故障时滤波器支路特定频点电流差异巨大,并且相对于很小的滤波器支路正常运行电流,故障电流变化明显,易于互感器检测,提高了保护灵敏度及可靠性。利用滤波器支路特定频点电流实现全线速动保护,对采样频率的要求低,易于工程实现。仿真结果表明,该原理能快速、灵敏、可靠地实现区内、外故障判别。

A new protection principle for HVDC transmission lines only using current signal of DC-filter is proposed in order to solve the problems of traditional protection principle using one-end data of HVDC,such as poor reliability and insufficient sensitivity.By analyzing the current of DC-filter at normal operation condition and the impedance characteristic of the electric network,which is made of reactance and DC-filter,it is found that the measured current is obviously different for special frequency signals when an internal or external fault occurs.Compared with the existing whole-line quick-action protection,the proposed protection principle uses the current of DC-filter,which is very small during normal operation and has significant changes between pre and post fault.Moreover the sample frequency is lower,and is easier to be implemented.Simulation results show that the proposed protection principle can identify external fault from internal fault.It can rapidly operate with high sensitivity and selectivity in different fault conditions.