电流互感器暂态特性对涌流传变的影响

在涌流期间,现场发生了多起变压器和相邻输电线路等电力元件差动保护误动的事故,严重威胁电网的安全稳定运行。原有误动分析中只考虑了变压器涌流暂态过程,少有考虑其与电流互感器等非线性铁磁元件电磁暂态交互作用过程。首先分析了变压器涌流波形特征量变化规律,并利用构建的工业保护用CT(P/PR)的Lucas仿真模型,仿真研究了CT暂态传变特性对涌流二次谐波比和间断角的影响规律。研究表明,涌流的二次谐波比与波形间断角取决于变压器铁心饱和角,饱和角越大,二次谐波比越小,而波形间断角越大,反之相反。经CT传变后涌流的二次谐波比变大,和应涌流波形间断角变小。励磁涌流波形间断角变化情况取决于负载电阻大小,可能变大,也可能变小。研究结论可为改进多非线性铁磁元件交互作用下变压器差动保护提供指导。

Effect of CT transient characteristics on transfer of inrush

During inrush period, multiple misoperation accidents of differential protection of power components such as transformers and adjacent transmission lines happened, which seriously threatened the safe and stable operation of power grid. In the traditional misoperation analysis, only the transformer transient inrush current process is considered, and the electromagnetic transient interaction between the transformer and other nonlinear ferromagnetic components such as CT is hardly considered. In this paper, the variation rule of transformer inrush current waveform characteristic is analyzed at first, and the influence rule of secondary load and type of CT on inrush current is simulated by using the simulation Lucas model of industrial practical CT (P/PR). The results show that second harmonic proportion of the inrush current and the dead angle of the waveform depend on the saturation angle of the transformer core. The larger the saturation angle is, the smaller the second harmonic proportion is, and the larger the dead angle of the waveform is. The second harmonic proportion of the inrush current becomes larger, and the dead angle of sympathetic inrush becomes smaller after CT transfer. The change of the dead angle of the inrush depends on the size of the load resistance, which may become larger and may be smaller. The conclusion can provide guidance for improving the differential protection of transformers under the interaction of multiple nonlinear ferromagnetic components. This work is supported by Science and Technology Project of Guangdong Power Grid Limited Liability Company (No. GDKJXM20162461).