针对风电系统中高频元件产生的高次谐波会影响变电站主变保护运行的问题,提出了一种变压器纵向阻抗虚拟相位保护的方法。该方法对故障分量电压平移后两侧的虚拟纵向阻抗求相位差,然后通过PSCAD(power system computer aided design)平...针对风电系统中高频元件产生的高次谐波会影响变电站主变保护运行的问题,提出了一种变压器纵向阻抗虚拟相位保护的方法。该方法对故障分量电压平移后两侧的虚拟纵向阻抗求相位差,然后通过PSCAD(power system computer aided design)平台搭建模型进行仿真进行验证。通过对比电压数据链可知:发生内部故障时,虚拟相位差大于90°;发生外部故障时,虚拟相位差小于90°。最后仿真结果表明:在区内故障发生时,虚拟相位差由0°变为180°,远大于90°,保护动作;当发生外部故障以及可能会影响到保护可靠性等因素时,虚拟相位差变化范围仅为0°~20°,远小于90°,保护不动作。故可基于此进行理论分析得出以下结论:内部故障能够可靠动作;在外部故障、电流互感器(current transformer,CT)饱和及励磁涌流产生时,即使有谐波的影响,保护仍不会动作。同时,现有误差精度为10%的CT能够满足此保护方法。仿真结果与理论分析一致,验证了在现有的CT精度下保护的正确性和可靠性以及较好的抗CT衰减能力。展开更多
This paper presents the influences of plasma layer on the oscillatory flow inarterial stenosis. The analysis demonstrates that the existence of the plasma layer mayobviously change the characteristics of flow such as ...This paper presents the influences of plasma layer on the oscillatory flow inarterial stenosis. The analysis demonstrates that the existence of the plasma layer mayobviously change the characteristics of flow such as velocity-profiles, longitudinalimpedance and pressure gradient, but hardly change the phase of longitudinalimpedance and pressure gradient. Besides. such influences vary with a and degree ofstenosis. These analyses have Special physiological significance in blood circulationsystem.展开更多
文摘This paper presents the influences of plasma layer on the oscillatory flow inarterial stenosis. The analysis demonstrates that the existence of the plasma layer mayobviously change the characteristics of flow such as velocity-profiles, longitudinalimpedance and pressure gradient, but hardly change the phase of longitudinalimpedance and pressure gradient. Besides. such influences vary with a and degree ofstenosis. These analyses have Special physiological significance in blood circulationsystem.
