4 KV motor control center power factor correction 1

[SS7]

We are currently thinking of major expansion,building a new plant with sepearte new 4 KV substation(25 MVA). To do power factor correction we can either have individual motors connected with terminal capacitors or bulk capacitance(in 2 banks) connected on Bus. The load pattern will be fairly stable(motors keeps running for atleast 4 months). From the same 4 KV bus we will feed to 480V LV substation where LV motors are connected. We do not have plan to fit capacitance on 480V level. All the motors, substation will be within 0.5 KM radius.
I would like to know the grounds on which method of power factor control is selected and your opinion on the desribed situation.
Thank you very much.

 

[jbartos]

Suggestion: Generically, the motor local pf compensation will result in higher initial costs; however, it will reduce losses due to RI**2 throughout the upstream power distribution from the local pf compensating capacitors.
The upstream centralized pf factor correction will probably cost less; however, the larger currents will be flowing downstream in comparison with the motor local pf compensation approach. The larger currents will cause larger RI**2 losses.

 

[Shortstub]

Another disadvantage to a common (or two banks) is the potential overvoltage resulting from over compensation by the capacitors, to some low load condition.