故障分量虚拟电压差夹角余弦母线保护方法

Cosine Bus Protection Method of Fault Component Virtual Voltage Difference Angle

针对母线比率差动保护在区内故障有汲出电流情况下,由于元件灵敏度下降导致保护整组动作速度减慢或拒动问题,采用故障分量虚拟电压差夹角余弦的母线保护新方法。该方法通过平移故障分量电压信号的位置,计算平移得到的两个故障分量虚拟电压差的夹角余弦来判别区内和区外故障。在区内故障时,故障分量虚拟电压差方向相反,夹角余弦值为负值;在区外故障时,故障分量虚拟电压差方向相同,夹角余弦值为正值。最后通过理论分析和PSCAD(power systems computer aided design)搭建拉西瓦水电站模型验证了新方法在母线内部故障有汲出电流时,其动作裕度至少为比率差动保护的5.97倍;通过平行四边形定则分析并仿真验证了新方法不受母线区内故障高阻抗接地影响;且方法具有较强的抗电流互感器饱和能力。

Aiming at the problem of slowing down or refusing to operate the whole group of protection due to the decrease of component sensitivity when the bus ratio differential protection has drawn current in the fault in the area,this paper adopts a new bus protection method of the cosine of the angle between the virtual voltage difference of the fault component.In this method,by translating the position of the fault component voltage signal,and calculating the cosine of the included angle of the virtual voltage difference of the two fault components obtained by the translation,the internal and external faults were discriminated.When there is a fault in the area,the fault component virtual voltage difference is in the opposite direction,and the cosine value of the angle is negative.When the fault occurs outside the area,the direction of the fault component virtual voltage difference is the same,and the angle cosine value is positive.Finally,through theoretical analysis and PSCAD(power systems computer aided design)to build the Laxiwa hydropower station model,it is verified that the action margin of the new method is at least 5.97 times that of the ratio differential protection when there is drawn current in the internal fault of the bus.The parallelogram rule is also analyzed and simulated.It is verified that the new method is not affected by the high-impedance grounding of faults in the bus area,and the method has strong anti-current transformer saturation capability.