某水电站机组主轴密封供水中断原因分析及处理

水电站机组经常因主轴密封供水中断的假信号引发保护误动而造成机组的非计划停运，从而影响机组的稳定运行以及电网对电站的考核。以越南某水电站机组主轴密封供水系统为例，对引起主轴密封供水中断的主要因素展开了分析，同时，对两种不同类型流量计的现场实测结果进行了对比。结果表明，电磁流量计误报是引起水电站事故停机的直接原因，而水电站内的电磁干扰及震动等则是引起电磁流量计误报的主要因素。由分析及对比结果可以看出，电磁流量计对使用环境的要求较高，因此，不推荐将其用于环境较为恶劣，特别是主轴密封供水系统对可靠性要求较高的水电站中。

Cause analysis of water supply break-off of main shaft seal of a hydropower plant unit in Vietnam and its treatment

Emergency shutdown accidents, due to the fake signals of break-off of water supply of main shaft seal, often occur to the generator units in the hydropower plant, which affect the stable operation of the units as well as the assessment of the hydropower plant by the grid. Taking the main shaft seal water supply system in a hydropower plant in Vietnam for example, the main factors that cause the break-off of the water supply for main shaft seal are analyzed. Through comparing the test results at site measured by two flow meters of different types, it is found that the fake signal sent by the electromagnetic flow meter is the direct cause of the units' emergency shutdown accident and that the electromagnetic interference and vibration inside the plant are the main factors causing the fake signal. The analysis and comparison reveal that the use of electromagnetic flow meter requires a fine environment of the hydropower plant, so it is not suggested to be used in the main shaft seal water supply system of hydropower plants that are in a harsh environment.