基于零序差动阻抗的输电线路保护新原理研究

Transmission line protection principle based on zero sequence differential impedance

针对现有的输电线路光纤纵联差动保护原理易受分布电容电流影响较大,且要求线路两端信息的严格同步的问题,研究了一种基于双侧信息的零序差动阻抗保护原理。给出了零序差动阻抗的定义为线路两端零序电压与零序电流比值之和。由理论分析可知区内故障时零序差动阻抗为两侧系统零序阻抗和的负值,阻抗位于第三象限,区外故障时零序差动阻抗为线路的阻抗,阻抗位于第一象限。根据零序差动阻抗的阻抗角构成保护判据。在PSCAD中搭建模型进行仿真实验,实验结果表明,零序差动阻抗保护原理不受对地电容电流和过渡电阻的影响,适用于带并联电抗器补偿的线路和弱馈电系统,并不要求两侧信号严格同步。

The optical longitudinal differential protection theory for transmission lines at present is affected easily by distributed capacitance current and requires rigid synchronization of double-terminal information of lines. The zero-sequence differential impedance protection principle based on bilateral information is proposed. The definition of zero-sequence differential impedance and the criterion of zero-sequence impedance differential protection principle are given. The zero-sequence differential impedance is equal to the opposite value of the sum of both sides system zero sequence impedance, which is in the third quadrant, when the fault happens within the protection zero. The zero-sequence differential impedance is equal to the transmission line zero sequence impedance, which is in the first quadrant, when the fault happens out of the protection zero. Some models are built in PSCAD to verify the correctness of the zero sequence differential impedance protection principle. Experimental results show that the criterion is not influenced by the fault resistance, and can be applied in the line with or without shunt reactor and weak feeding system, and the strict synchronization of the sampled data is not needed.