基于单端暂态电流和差比的柔性直流配电系统断线保护

直流配电系统单极断线故障特征不明显,现有的单极断线保护依赖单一电气量量测,难以通过定值整定准确可靠地识别故障线路。文中提出一种基于单端正负极电流和差比的新型断线保护。通过分析四端直流配电系统开环与闭环运行模式下单极断线的故障机理,得出单极断线故障下故障极与非故障极线路电流的变化差异,进一步利用两者线路电流的和与差作商放大故障极与非故障极的差异,达到可靠识别故障极线路的目的。所提保护原理简单,计算量小,避免了定值无法整定的问题,基于本地测量信息即可实现快速故障识别与选极。最后,通过仿真验证了该方法的可靠性。

Line Breakage Fault Protection Based on Ratio Between Sum and Difference of Single-ended Transient Current for Flexible DC Distribution Systems

The characteristics of line breakage fault in DC distribution system are not distinctive compared with normal operation. The existing line breakage protections which rely on the single-terminal electrical quantity is difficult to identify the faulty line accurately and reliably. This paper proposes a novel protection method for line breakage fault based on ratios between sum and difference of single-ended positive and negative currents. By analyzing the characteristics of line breakage fault in open-loop and closed-loop operation modes of a four-terminal DC distribution system, the differences of line currents between fault pole and non-fault pole can be obtained when line breakage fault occurs. The differences between fault pole and non-fault pole are amplified by the ratios between sum and difference of the line currents to identify the fault pole reliably. The proposed protection principle is simple, straightforward and can avoid the setting calculation problem. In addition, fault identification and pole selection can be achieved quickly based on local measurement information. Finally, the reliability of the proposed method is verified by simulation results.