×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Distribution Capacitor Bank

Distribution Capacitor Bank

Distribution Capacitor Bank

(OP)
I retrieved some recloser data yesterday for one of the feeders.  The data was showing

Phase A: PF=0.95, kW=258, kvar=85, KVA=269

Phase B: PF=0.56, kW=237, kvar=-346, KVA=421

Phase C: PF=0.51, kW=213, kvar=-356, KVA=416

The power factor on b and c phases were of some concern, and was considering a cap bank.  What size cap bank would be ideal for this case.  I was thinking of a 300 KVAR bank.  I have never dealt with capacitor banks on the distribution feeder level, so any of your input is appreciated.

RE: Distribution Capacitor Bank

First thing I'd do with that data is make sure everything is connected correctly.  I find your numbers highly suspect; not that I doubt they were written down correctly, but Garbage In, Garbage Out.

RE: Distribution Capacitor Bank

The negative kVARs would generally indicate a leading power factor, which is unlikely, but not impossible.  

I agree with David Beach that you should verify the connections are correct and the controller is properly configured.  

If the pf is truly leading, adding caps is only going to make it worse.  

RE: Distribution Capacitor Bank

It looks like there is a mismatch in your phase B and C currents and voltages.  If you take the phase A data and add 120 degrees the power factor comes out about .50 which is nearly what you're reading on phase C and from a simple phasor diagram you can see it will come out leading.  I suspect a rolled phase.

RE: Distribution Capacitor Bank

Did the recloser give any amp or voltage data to cross check the values?  I agree with the other gentlemen, it looks like a rolled phase providing bogus metering data.

RE: Distribution Capacitor Bank

Is it possible that you already have a capacitor bank on this lightly loaded line and one fuse is blown on it? The theory about a rolled phase might explain the bad Kvars, but your Kw would be equally out of wack.

RE: Distribution Capacitor Bank

I like wfowfo's suggestion.  But I still say that you need to explain the numbers before doing anything about them (or with them).

RE: Distribution Capacitor Bank

Wouldn't a rolled phase still provide the same KVA reading on all 3 phases?

A blown fuse on an existing cap bank really does sound like a reasonable problem. Could it be a blown fuse on one of the metering PT's?

In any case, the imbalance of the system measured by the meter would indicate the metering is wrong.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources