沙角C电厂3 kV变压器保护误动作故障分析

Analysis of Malfunction of 3 kV Transformer Protection in Shajiao C Power Plant

沙角C电厂3 kV磨煤机电机在3号机组正常带负荷时出现其中一相接地报警,与之相关联的母线在报警期间有保护动作,使得整条母线上的重要电机负荷停止工作,进而使该厂的3号锅炉MFT。运行人员在问题发现后的第一时间赶往现场检查,发现故障出现在3 kV工作变压器上。原因是变压器的这一级零序差动保护本不应该在下一级电机出现故障时动作。本文分析了保护越级误动的起因,并制定保护改造方案,防止事故再次发生。

The three-kilovolt coal mill motor in our plant has a grounding alarm for one of the phases when the No.3 unit is normally loaded,and the associated bus has a protective action during the alarm period,which makes the important motor load on the entire bus stop Work,and then make the factory’s No.3 boiler MFT.The operating personnel rushed to the site for inspection as soon as the problem was discovered,and found that the fault occurred in the three-kilovolt working transformer.The reason is that this level of zero sequence differential protection of the transformer should not act when the next level of motor fails.This article analyzes the cause of the protection leapfrog and makes a protection reform plan to prevent the accident from happening again.