Over Frquency happened at a windy winter night..

SUNDAY, DECEMBER 12, 2010

“ at 3:00 am , A sudden frequency fluctuation happened , that cause the MW output fluctuate with the grid frequency , Unit 7 was at Coordinated Mode ( Boiler Master – Auto  , Turbine Set – Auto ) ,  The load fluctuated accordingly to the frequency from 105 MW to 90 MW, and increased to 105 MW.

After a little time, frequency reached 50.1 HZ – therefore the MW output reached 20 MW,

Also, Boiler Master responds by reducing Air Flow and Fuel Gas Flow for the boiler. The load still decreased until it reached 2 MW, and to (-2 MW), without coming the signal of Reverse Power.

At this instant we trip the turbine manually.

We wanted to conserve the boiler to be in service, but HP-TBV opens widely within 30 sec., and sucking all drum level to +267 mm, resulting MFT Protection to the boiler.

The first out indication of MFT at BMS was (Drum level HH). “

There were a lot of discussion and arguments about what is the cause of this accidents , and what should operators do ?

I attached A chart Table shows the different parameters changed at each same time !! , If any one has an opinion about what happened , plz tell me !!



TREND_OPERATION_PARAMETERS