×
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

Help - 130kV OHL Disturbance

Help - 130kV OHL Disturbance

Help - 130kV OHL Disturbance

(OP)
Hi,
I received from a colleague the attached disturbance " 130kV OHL short circuit".

My question is :
Why during the short circuit the phase A and B and C currents are in phase ?!?!

Any idea ???

Thank you for your support.

Marco

RE: Help - 130kV OHL Disturbance

If A, B, and C are all in phase you are looking at the results of a ground fault.

RE: Help - 130kV OHL Disturbance

The voltage traces appear to be due to a fault between line 1 (red) and ground. But the current traces show some odd current reading on line 3 (green). For a line to line fault, I'd expect to see the two line currents out of phase by approximately 180 degrees. Which is not the case here.

I'd need to take a close look at how the CTs are connected to understand whether this is an actual reading or some artifact of the wiring scheme.

RE: Help - 130kV OHL Disturbance

Marco.
Could youy please send us Comtrade file, intresting see vektor diagrams before--after fault.
Best Regards.
Slava

RE: Help - 130kV OHL Disturbance

Like I said, it is a line to ground fault as seen from a location on a network.  If you're used to looking at faults on radial systems it will seem very weird to have all three phases line up, but in networked systems it is not at all uncommon.  Draw out your sequence diagrams and you will see that (+), (-), and (0) are all approximately in phase and can be of similar magnitudes, resulting in all phases being of similar phase and magnitudes.  Pick the right impedances in front of, and behind, the fault and you can get most any set of currents you can dream up.

RE: Help - 130kV OHL Disturbance

This is probably one of two or more sources of the fault current.  

If this was the only source to a Ø-grd fault, there would be current only in the faulted phase.  If it was measuring the current coming from a grounding transformer, it would show all zero-sequence current and all phases would be in phase and equal.

You can get some screwy looking currents in each source when you have multiple sources feeding a fault.
 

RE: Help - 130kV OHL Disturbance

Hmm. Grounding transformer. Any change its something like a zig zag configuration? And where are these measurements being made w.r.t this transformer (if it exists)?

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