耐受高阻和强噪声的柔直配电线路保护原理

Protection Scheme for Flexible DC Distribution Lines With High Resistance and Strong Noise Endurance Ability

针对柔性直流线路保护存在高阻故障识别速度慢、故障电流叠加噪声干扰时识别可靠性低的问题,提出一种基于电流相关性的线路保护原理。首先分析了不同故障类型的线路短路电流特征,据此,采用正负极电流累加和辨识故障类型,利用电流Pearson相关性判断故障位置。其中,相关性判据基于滤波的本地电流,通信通道仅传输线路两端判别逻辑量,对信号同步要求低,且能够有效抑制噪声影响。最后,在PSCAD/EMTDC验证所提方法可行性。结果表明该方法能够利用0.5 ms数据窗内线路电流可靠识别有无强噪声干扰的金属性短路和高阻接地短路,且不受交流侧故障、非故障投切重负荷的影响。

Aiming at the problems of slow speed and low reliability of high impedance fault identification with noise interference in flexible DC distribution line protection,we propose a line protection scheme based on the current correlation.First,the characteristics of line short-circuit current under different fault types are analyzed.On this base,the current accumulation of positive and negative poles is used to identify the fault type,and the current Pearson correlation coefficient is used to identify the fault location.The correlation criterion is based on the filtered local current.The communication channels only transmit the discrimination logic values at both sides of the line,which have low requirements for signal synchronization and can effectively suppress the noise interference.Finally,the feasibility of the proposed scheme is verified by PSCAD/EMTDC.The result shows that this scheme can reliably identify metallic short-circuit fault and high impedance grounding short-circuit fault with/without strong noise interference in the 0.5 ms data window of line currents,and is not affected by AC side faults and non-fault switching heavy loads.