基于虚拟电流波形特征的母线保护原理

摘要

采样值差动保护直接对离散采样值进行差动判别，计算量小且动作迅速，但易受干扰影响，其可靠性需要深入研究。针对此现状，在研究采样值差动的基础上，提出了一种基于虚拟电流波形特征的母线保护原理。通过合并同时刻方向相同的各支路故障分量电流采样值，将多支路电流等效合成为2个虚拟电流，根据虚拟电流在母线不同运行状态下的波形特征差异，引入相关技术对其进行定量分析，利用多点相关度的大小和分布情况来区分母线区内外故障。理论分析和动模实验表明，该判据能快速可靠地切除母线故障，不受故障类型和区内故障流出电流的影响，并具有一定的电流互感器(TA)饱和识别能力。%Sample value differential protection has the advantage of being capable of making the differential protection characteristic work by directly using the instantaneous sample value,which requires less calculation and operation time,but it has the disadvantage of easily being affected by interference and its reliability should be studied.In order to solve this problem, an algorithm based on virtual current for bus-bar protection is proposed based on the research achievement in the sample value differential protection.By merging the sampling values of the branch fault component currents of the bus-bar of the same moment and in the same direction,the bus-bar system is simplified into two virtual currents.Based on the waveform differential attribute of the virtual currents in different bus-bar operating modes,the differences are quantitatively analyzed using the correlation analytic technique.By calculating the correlation coefficients of sampled current values and utilizing their distribution characteristics,the external and internal faults can be correctly distinguished.Results of theoretical analysis and simulation have proved that the proposed criterion is capable of rapidly and reliably distinguishing internal fault from external fault,while insensitive to current transformer(TA) saturation to a definite extent.