直流馈入影响下交流输电线路的纵联保护方案

Pilot Protection Scheme for Alternating Current Transmission Lines under the Influence of Direct Current Feed-in

针对直流系统馈入会导致电流差动保护的动作量减少、制动量增加,从而降低保护动作可靠性的问题,提出基于纵联阻抗的交直流混联系统纵联保护方案。通过分析考虑直流馈入影响下不带并联电抗器的交流输电线路故障模型,得出保护安装处差动电流、电压的电气量在区外故障时呈现容性,在区内故障时呈现阻感性的结论。在此基础上推导建立了区内外故障下的纵联阻抗表达式,提出基于纵联阻抗幅值及相角的保护判据,该保护判据不受直流馈入的影响,整定原理简单,具有良好的抗过渡电阻能力,在技术上便于实现。仿真结果表明了所提判据能够快速、有效地区分内部与外部故障,可靠保护线路全长。

Aiming at the problem that the feed-in of the dirrect current(DC)system will reduce the action amount of the current differential protection and increase the braking amount,thereby reducing the reliability of the protection action,a longitudinal protection scheme based on the longitudinal impedance of the AC/DC hybrid system was proposed.Through analysis and consideration of the alternating current(AC)transmission line fault model without shunt reactors under the influence of DC feed-in,it was concluded that the electrical quantities of the differential current and voltage at the protection installation are capacitive when the fault occurs outside the area,and appear resistive and inductive when the fault occurs inside the area.On this basis,the expression of the longitudinal impedance under the internal and external faults was derived and established,and a protection criterion based on the amplitude and phase angle of the longitudinal impedance was proposed.The protection criterion was not affected by the DC feed-in.Good resistance to transition resistance,technically easy to achieve.The simulation results show that the proposed criterion can quickly and effectively distinguish internal and external faults,and reliably protect the full length of the line.