基于分布参数频域模型识别的纵联保护原理

Transmission Line Pilot Protection Based on Frequency-domain Model Identification of Distributed Parameter

为消除高压长距离输电线路的分布电容电流对线路保护的影响,为此,基于矩阵束能够可靠地提取故障线路特征频点信息的特点以及模型识别的保护理论,提出了一种输电线路纵联保护新原理。该原理首先根据分布参数线路的故障网络分析,建立出区内外故障的故障模型,区外故障模型为分布电容模型,区内故障模型为等效系统阻抗模型。进而定义了2种不平衡电流并将其分别作为2种模型的模型误差来识别故障模型。区外故障时,故障数据符合分布电容模型,其不平衡电流小于等效系统阻抗模型的不平衡电流;区内故障时,故障数据符合等效系统阻抗模型,其不平衡电流小于分布电容模型的不平衡电流,据此可以判断出区内外故障。理论分析及仿真结果表明,新原理能够快速可靠地切除区内故障,且不受电容电流和过渡电阻的影响。

To eliminate the capacitive current＇s influence on line protection of long-distance and high-voltage transmission lines, this paper proposed a novel transmission line protection scheme based on model identification method and on the point that matrix pencil algorithm can extract the characteristic frequencies of the transmission line reliably. By studying the fault network topology of distributed parameter lines, the frequency-domain models of external and internal fault states were built. The fault model for external fault states is a distributed capacitive model, while the fault model for internal fault state is an equivalent system impedance model. The two kinds of unbalanced currents were defined as two model errors to identify different fault models. When an external fault occurs, the fault data corresponds with the distributed capacitive model and its unbalanced current is smaller than that of the equivalent system impedance model. When an internal fault occurs, fault data corresponds with the equivalent system impedance model and its unbalanced current is smaller than that of the distributed capacitive model. Therefore, external and internal faults are distinguished. Theoretical analysis and simulation results show that the new principle can remove internal fault quickly and reliably, free from the influence of capacitive current and transition resistances.