IT IS A NORMAL PRACTICE TO START THE CENTRIFUGAL PUMP WITH ITS DISCHARGE VALVE CLOSED. THE REASON BEHIND THIS CAN BE FOUND OUT BY LOOKING AT THE CHARACTERISTIC CURVE OF CENTRIFUGAL PUMP.
WHEN THE DISCHARGE VALVE IS CLOSED, THAT TIME QUANTITY DISCHARGED IS ZERO, AND AT THAT TIME POWER CONSUMED IS LEAST. HENCE THE CURRENT DEMAND IS LEAST.
THIS ALSO HELPS IN REDUCING VOLTAGE DIP OF GENERATOR.