超长距离HVDC线路高灵敏性主保护

High Sensitive Main Protection for Extra-long HVDC Line

高压直流输电(highvoltagedirect current,HVDC)线路故障的快速识别对系统的安全稳定运行具有重要的意义。随着大容量远距离输电需求的日益旺盛,目前已出现多条超长距离HVDC线路。如直接将传统HVDC直流保护应用于超长HVDC线路,其在灵敏性和速动性上尚难达成统一。为解决该问题,该文在对线模行波的色散现象分析的基础上,提出一种基于本地量、足够灵敏、且能够在超短窗内实现故障识别的主保护原理:首先利用正方向/反方向故障工况下前行波与反行波在能量比值上的差异性,设计一种能够精确表征波头到达时刻的启动判据;在此基础上,基于同模异频时差特征提出一种HVDC输电线路的单端量测距式主保护原理。理论分析及仿真结果表明,所提出的保护原理能够适用于900km以上的超长距离输电线路;线路长度越长,其动作性能更加优异,可有效弥补现有主保护应用于超长距离输电线路时的灵敏性问题、以及纵联式保护的速动性问题。

The rapid identification of high voltage direct current(HVDC)faults is of great significance to the safe and stable operation of the system.With the increasing demand for large-capacity long-distance transmission,multiple ultra-long-distance HVDC lines have appeared at present.If the traditional HVDC DC protection is directly applied to the ultra-long HVDC lines,it is difficult to reach a consensus on its sensitivity and rapidity.In order to solve this problem,based on the analysis of the dispersion phenomenon of the line-mode traveling wave,a type of main protection based on the local electrical quantity was proposed,which is sensitive enough and can identify the fault in a very short period of time window.Firstly,by using the energy ratio difference between the forward and the backward traveling waves under the condition of forward/reverse fault,a start-up criterion,which can accurately represent the arrival time of the wave-front was designed.On this basis,based on the characteristics of the same-mode different-frequency time difference,a single-ended location-type main protection principle for HVDC transmission lines was proposed.Theoretical analysis and simulation results show that the proposed protection principle can be applied to ultra-long-distance transmission lines of 900 km and above.The longer the line length is,the better the operating performance will be,which can adequately compensate for the sensitivity of the existing main protection applied to ultra-long transmission lines and the rapidness problem of the pilot protection.