特高压直流输电线路差动保护改进方案

Improved scheme for differential protection of UHVDC transmission lines

提出一种差动保护改进方案,利用特定电压、电流数据与线路电阻三者间可等效转换的特定电气三角平衡关系,辅以积分算法具有的低通滤波效果,将线路两端突变量差流作为动作量,将线路两端电压突变量差与线路电阻之比作为制动量,构造改进判据.理论分析表明,当线路发生区外故障时,动作量明显小于制动量;线路内部故障时,动作量大于制动量,判据设置清晰、明确.该方案对采样频率要求不高、整定简洁、结果清晰且不受分布电容电流的影响.以我国±800 kV特高压工程为参照搭建仿真模型,设置3种典型故障对保护判据进行仿真验证.结果表明,所荐方案具有可靠性高、判别灵敏的特点,能准确、快速地识别区内、区外故障,具有较好的工程运用前景.

An improved scheme of differential protection was proposed,which utilized the relationship of equivalent electrical triangle balance among the specific voltage data,current data and line resistance,combined with the lowpass filtering effect of the integral algorithm.To construct improved criterion,the differential currents at both ends of the line was taken as the action amount,and the ratio of the difference of the voltage at both ends of the line to the line resistance was used as the braking amount.Theoretical analysis shows that,for external faults,the movement is significantly less than the brake;for internal faults,the movement is greater than the brake,the criterion can be set in a simple and clear way.Meanwhile,the proposed scheme is insensitive to the sampling frequency and independent of distributed capacitive current.The simulation model makes reference to a±800 kV UHVDC in China.Three typical faults were set on the simulation model to prove correctness of the criterion.The simulation results show that the recommended scheme has the characteristics of high reliability and sensitivity,and can recognize the external or internal fault precisely and rapidly,and has good engineering application prospect.