基于电流极性和相对熵的广域继电保护新算法

New Algorithm of Wide-Area Protection Based on Current Polarity and Energy Relative Entropy

为了提高广域继电保护的容错性和灵敏度,结合母线采样值保护和线路故障分量差动保护原理,提出一种基于电流极性和能量相对熵的广域继电保护新算法.首先,对线路IED保护关联域进行划分,针对不同关联域,提取正序工频故障分量电流,并给出关联域边界电流、综合计算电流和综合虚拟电流概念;其次,定义综合电流采样值能量相对熵,量化综合电流的差异程度,同时,通过求取关联域边界电流之间的夹角大小来表征边界电流的极性关系,并利用电流采样值能量相对熵和极性关系识别关联域内外故障;最后,利用PSCAD/EMTDC软件搭建IEEE-3机9节点系统模型,分别在不同故障点设置不同故障类型进行仿真检验算法性能.研究结果表明:在关联域区内故障时,综合电流几乎一样,相对熵值很小,接近为0;边界电流间夹角小于π/2,极性近似相同;区外故障时,综合电流波形及采样值能量差异显著,相对熵值大于1;边界电流间夹角接近于π,极性近似相反,二者差异明显;域内单相接地故障时,在800Ω的高阻条件下,相对熵最大为0.428,夹角最大为0.388,仍能可靠满足判据,具有较高的灵敏度.实验结果验证了本文算法性能基本不受过渡电阻的影响,能较好克服TA饱和、数据畸变等不利因素的影响.

In order to improve the fault tolerance and sensitivity of wide-area relay protection, a new algorithm of wide-area relay protection based on current polarity and energy relative entropy was proposed. It combines bus-bar sampling value protection with differential protection principle for fault component of lines. Firstly, the protection correlative domain of line IED was divided, so that the fault component currents of positive sequence frequency were extracted accurately according to different correlative domains. Meanwhile, the concepts of boundary current, synthetic calculated current and synthetic virtual current were presented. Secondly, the energy relative entropy of the synthetic current sample was defined to quantify the difference of the synthetic current. At the same time, the angle between the boundary currents of the correlative domain was calculated to characterize the polarity relation of the boundary current, and the correlation between the current sample energy entropy and the polarity relation was utilized to identify the inner and outer faults of the correlative domain. Finally,utilizing IEEE 3-machine and 9-bus system constructed by the software of PSCAD/EMTDC, different fault types were set at different fault points to test eh algorithm performance . The results reveal that when fault occurs in the correlative domain, the synthetic current is almost the same, with the relative entropy being very small, close to 0, and the angle between the boundary currents is less than π / 2 with approximate polarity. When the fault is outside the domain, the synthetic current waveform is significantly different from sampling value, with the relative entropy larger than 1,and the angle between the boundary currents is close to π , with nearly opposite polarity. The distinction between the faults inside and outside the domain is obvious. Simulation results show that when single-phase earth fault occurs in the domain, the maximum relative entropy is 0. 428 and the maximum angle is 0. 388 in the condition of high resistance of 800 Ω , which still meets the reliable criterion and has high sensitivity. The experimental results verify that the algorithm performance is basically not affected by the transition resistance, and can overcome the influence of unfavorable factors such as TA saturation and data distortion.