一次自动空气开关跳闸引起停机事故的分析

Analysis of a shut-down accident caused by automatic air switch trip

论述了某电厂#7机组6 kV厂用工作段电压互感器二次回路自动空气开关跳闸后,由分散控制系统(DCS)逻辑判断为厂用段失压跳开厂用6 kV电源开关,在工作段失压切换过程中,瞬间失电使运行中的给煤机跳闸,导致主燃料切断保护(MFT)动作,最终造成了机组与系统解列的故障。分析了此次停机事故的原因,提出了避免发生类似故障的措施。

In a certain power plant,after an automatic air switch in secondary circuit of potential transformer of 6kV auxiliary working bus section of No.7 unit trip was discussioned.The distributed control system had mistake the fault for that the voltage of auxiliary working bus section is cut off,and sent out operation instruction to trip the 6kV power breaker.In the process of voltage interrupt and transfer of working bus section,the coal feed breaker tripped due to the momentary voltage interrupt,and this lead the main fuel tripping protection breaker to trip.At last,the Unit was disconnected with the system.The reason of this accident outage was analyzed,and the preventive measures of similar accident were proposed.