发电电动机励磁绕组匝间短路故障在线监测

摘要

As the general schemes of online excitation winding inter-turn short circuit monitoring take all the fractional harmonic components of imbalanced stator neutral-point current as the monitoring variables to form the corresponding alarm threshold,they are not sensitive enough to the short circuit across a few turns due to the higher alarm threshold.With the generator/motor of Yixing pumped storage power station as an example,the imbalanced stator neutral-point current caused by the short circuit across a few turns of excitation winding is calculated,the inherent imbalanced stator neutral-point current in normal operating condition is measured,and an improved online monitoring scheme is proposed,which only adopts bigger harmonic components,i.e.three-eighths and five-eighths harmonic components,to form the alarm threshold.Simulative results show that,with higher sensitivity than the general schemes,the improved scheme issues alarm for the excitation winding inter-turn short circuit of 3 ％ turn-ratio and above.The online monitoring equipment based on the improved scheme for generator/motor No.4 of Yixing pumped storage power station has been successfully put into operation.%通用的励磁绕组匝间短路故障在线监测方法未加分辨地采用定子中性点不平衡电流中的所有分数次谐波分量构成监测量及相应的报警值,可能因报警值较高而对小匝数故障不够灵敏.以江苏宜兴抽水蓄能电站发电电动机为例,计算小匝数励磁绕组匝间短路故障引起的定子中性点不平衡电流并实测正常工况下固有不平衡电流,在此基础上提出了一种改进的在线监测方案,提取由匝间短路引起的不平衡电流中含量较高的3/8次和5/8次谐波电流构成报警值.仿真计算结果表明,对于江苏宜兴抽水蓄能电站发电电动机,改进的在线监测方案能对3％及以上匝比的励磁绕组匝间短路故障发出警报,灵敏性优于通用监测方案.基于所提改进方案的在线监测装置已经成功投运于江苏宜兴抽水蓄能电站4号发电电动机.