700MW机组厂用电切换失败导致机组解列的事故分析及防范措施

Analysis on unit disconnection accident of 700 MW unit caused by switchover failure of auxiliary power and preventive measures

某电厂700 MW机组并网后厂用电切换失败,1A定子冷却水泵因母线失电故障停运,1B定子冷却水泵虽然自启,但仍然发出定冷水差压低信号,保护动作导致发电机解列。对保护动作原因进行了深入分析,发现了隐患,从联锁保护逻辑优化、更换新型仪表、制订反事故措施等3个方面提出防范措施,有效消除机组运行的安全隐患。

After the 700 MW unit of a power plant had been connected into grid,the auxiliary power switchover had failed;due to the bus voltage loss,the 1A stator cooling water pump was stopped;although the 1B stator cooling water pump started automatically,but the stator cooling water pressure difference low signal had been given out,and protection device had tripped and caused the generator disconnection from the power system.The reason of the protection trip was analyzed in depth;and the hidden dangers were found.Some prevent measures were proposed with 3 aspects of measures such as optimizing the interlock protection logic,replacing the instruments by new type instruments and formulating anti-accident measures;and the safety hidden dangers for unit operation were eliminated effectively.