×
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

High unbalanced generator phase currents
3

High unbalanced generator phase currents

High unbalanced generator phase currents

(OP)

Has anyone seen a phase unbalance of the scale of 575 Amps, 380 A, 370 A (these currents are estimates but close to actual) at the output of an AC synchronous generator?

A methane gas (dairy digester) powered CAT engine running at 1200 rpm provides power to a 5 MVA generator. The generator step up transformer is a padmount 277VLN/480VLLY-12.47Y kV connected directly to utility 12.47 kV, 3 phase, 4 wire, distribution system via a dedicated (generator to utility feeder) 15 kV class, 1000 ft long, underground cable. The dairy farm is located miles away from the substation at the end of the (radial) 3-phase feeder with small size conductor. The utility's feeder serves other customers including a few small industrial, commerical and other farms.

RE: High unbalanced generator phase currents

Not having vectors or anything else, I'd be concerned you have an open phase on the 12.47kv side.

That is assuming the stepup is a delta-wye.

RE: High unbalanced generator phase currents

2
The circuit is not evenly loaded, by the time it makes it to your site the phase voltage balance is not an even 120° between phases all the way around.  I've seen similar, even to the point of current out on two phases and in on the third.

RE: High unbalanced generator phase currents

One of the problems with a wye-wye connection to the utility is that the generator zero-sequence impedance is relatively low compared to its positive-sequence impedance.  This makes the zero-sequence path through the generator low and the generator can end up powering a lot of the utility unbalanced load.  There may also be unbalanced phase voltages on the utility system because of single phase voltage regulators that aren't set properly.

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