一起低频减载误动作事件分析及改进措施

Analysis of A Low-frequency Load Shedding Misoperation Event and Its Improvement Measures

集成于线路保护装置的低频减载功能作为电力系统最后一道防线具有重要意义且应用广泛,但低频减载功能误动作时有发生。为提高配电网供电可靠性,文中针对一起低频减载误动作事件起因进行分析,发现铁磁谐振为误动作诱因,同时从保护装置二次回路角度出发,分析认为装置存在小PT饱和、计算误差等问题导致相间电压频率计算出现偏差,进而引起低频减载功能误动作。通过电磁仿真手段对误动作原因进行验证,其仿真结果与误动作事件实际录波吻合。最后,依据误动作原因,从改善装置电压采样、优化频率计算等方面提出了4点改进措施。

The low-frequency load shedding function integrated in line protection device is of great significance and widely used as the last line of defense in power system, but the misoperation of low-frequency load shedding function occasionally occurs. In order to improve the power supply reliability of distribution network, the causes of a low-frequency load shedding misoperation event are analyzed, in which ferromagnetic resonance is the cause of misoperation. From the perspective of secondary circuit of protection device, it is analyzed that the small PT saturation and calculation error lead to the deviation of phase-to-phase voltage and frequency calculation, which causes the misoperation of low-frequency load shedding function. The causes of misoperation are verified by electromagnetic simulation respectively, and the results are consistent with the actual recording of misoperation event. Finally, according to the causes of misoperation, four improvement measures are put forward from improving voltage sampling and optimizing frequency calculation.