Cause Analysis and Improvement of an Unsuccessful FCB Test on 660 MW Ultra-Supercritical Coal-Fired Unit
Cause analysis is made for the trip of over-speed protection action in the first FCB test on one 660 MW ultra-supercritical coal-fired unit.As indicated,in the SAIC Siemens/Ovation system combined unit,DEH load shedding control logic is complex and the scan time of communication points between controller stations is long.Consequently,after the generator's splitting signal is issued,the trip electromagnetic valve in low-/medium-voltage adjusting valve receives the trip command after a longer time,then adjusting valve closes with time lag,causing the unit over-speed trip.Therefore,this paper proposes to directly de-energize the trip electromagnetic valve for 1 s after the generator's splitting to shorten signal-receiving time and ensure the FCB test success.
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