高压直流线路低电压保护判据定值调整研究

摘要

依托国内某±500kV高压直流输电工程,对直流线路高阻接地故障进行理论建模和PSCAD/EMTDC仿真研究.分析结果表明,在线路低电压保护判据定值固定时,高负荷下的接地阻抗检测范围过小,可能出现保护拒动;低负荷下的接地阻抗检测范围过大,可能出现保护误动.以交流电网的相关规程为参考,提出了改进建议.根据不同负荷状况对线路低电压保护判据定值进行调整,调整的标准是检测出不高于300 Ω的高阻接地故障.仿真结果证明这样的调整是有效的.%Basedonadomestic±500kV HVDC project, the theoretic equivalent model and PSCAD/EMTDC simulation of DC line high-impedance earth fault are evaluated. The results show that on condition of fixed criterion settings of line low-voltage protection,the detected scope of high-impedance is too small when the system operating at high load, and it may cause miss-trip; when the system operating at low load, the scope is too wide, which may cause protection maloperation. Based on relevant standard of AC-system,the suggestion of adjusting the criterion settings according to different load situations is proposed and the standard of adjustment is that the earth fault with high-impedance less than 300 Ω should be detected. Simulation results show the effectiveness of the adjustment.