核电半速汽轮机冲转过程跳机事件分析及处理

Analysis and Treatment of Vibration Trip During Start⁃Up of Half⁃Speed Turbine in Nuclear Power Plant

某核电半速汽轮发电机组临时停机后,在冲转升速过程中,2号低压转子5号轴承振动达到保护定值,引发跳机。通过分析振动数据、系统参数,以及调查检修数据等,判断跳机的原因为:汽轮机轴封系统发生波动,引起转子受力不均和圆周温差不对称,所导致的转子临时性热弯曲引发了动静摩擦,从而引起盘车转速及暖机转速下5号轴承轴振异常增大,在升速至临界转速时,共振效应使汽轮机振动急剧增大。制订了冲转过程中的汽轮机参数监控方案,并延长盘车时间以消除转子临时性热弯曲,待转子状态恢复后再冲转,汽轮发电机组得以启动成功。分析过程和处理结果可为汽轮机冲转过程振动监测及异常干预措施的制订提供参考。

A nuclear power half⁃speed turbine generator unit had a temporary shutdown,and during the start⁃up process,a trip was caused by excessive vibration of No.5 bearing at low pressure No.2 rotor.Analysis was carried out on vibration data and system parameters,and maintenance data was also investigated.Based on this,it was concluded that the uneven stress and asymmetric temperature difference around circumference of the rotor caused by fluctuation of turbine shaft seal system was the reason of the thermal bending of the rotor,which leaded to friction between rotating and stationary parts,so the vibration of No.5 bearing increased abnormally during the turning and warming up process.Thereafter,the turbine vibration was increased sharply because of the resonance effect at the critical speed.Corresponding program was made up to monitor the steam turbine parameters during start⁃up,and the turning time was lengthened to eliminate the temporary thermal bending of rotor.After recovery,the turbine generator unit started up successfully.The analysis result and treatment can provide reference for vibration monitoring and abnormal intervention during the start⁃up of steam turbine.