Unit trip caused by third BFP started

Boiler Feed Pump is the largest of capacity motor on 10kV board. It could be auto start when second of BFP trip or it could be manual start when BFP changed over.

This happened when unit on 90%load and BFP current which in service had 500A and third BFP initiated had starting current 1265A. The 10kV board dropped from 9.9kV to 8.6kV and 380V board dropped to 341V.

The 380V incoming CB got under-voltage alarm that initiate to open the incoming CB and inter-tie CB was late to close.

Actually the voltage drop when third of BFP start already estimation save in operation although in unit full load.

From table above show that board 380V on case A got high degradation and it could be avoid by increase voltage on board 10kV.