Capacitor Banks on distribution poles? 1

[arcnatural]

Hello everyone,

I've always been curious to why you would want to have capacitor banks out on a distribution pole feeder as opposed to within a substation. Could anyone tell me why this is a common practice?

Regards,

John

 

[davidbeach]

Because there more useful out there. Much better voltage profile on the feeder that way.

 

[bwen08]

If all the VAR draw is at the end of the line, would you rather put the bank close to the load or all the way back at the substation and have more line loss? Also, if the feeder is changed to an alternative source, your would lose your power factor correction if you had a substation based cap bank.

 

[QBplanner]

sometimes, substation within cities has limited space so we plan the Vars installed on D feeder poles.

 

[tinfoil]

The POINT of the cap bank is to minimize current flow (and subsequent I^2*Z losses).

Having the capacitors out where the inductive VARs are 'flowing' (due to cumulative inductive loads on the feeder) tends to bring the local power factor towards (and hopefully not past) unity, minimizing the currents.

Your 'perfect goal' is to have just enough current to deliver all of the customer's Watt needs at every point along the lines.
Practicality means a limited number at strategic points based on that feeders load profile.

 

[jghrist]

If the reason for the capacitors is to reduce losses or improve voltage, then as others have said, the best place is out on the line closer to the load. If the reason is to meet a power factor requirement from the supplier, then it will be easier to meet changing reactive load requirements with switched capacitors at the substation. You will, for the most part, lose the side benefits of lower losses and better voltage regulation.