×
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

LG earth fault current of DG set

LG earth fault current of DG set

LG earth fault current of DG set

(OP)

Solidly gorunded DG set contributes say xkA for L-G fault.
This values comes assuming ground grid resistance as 0.

If the ground grid resistance which is normally 1-5 ohms for earthing calculations, is added to zero sequence impedance of DG L-G fault value reduces drastically.

Is it possible to consider ground grid resistance for L-G faults?

RE: LG earth fault current of DG set

No.

During a ground fault the current does not necessarily flow through the "earth" or the grounding electrode. Draw a diagram and review.

The generator frame/ground bus is normally bonded through the equipment grounding conductors with the circuit. The neutral is solidly bonded to the ground bus. So the most likely impedance of the ground circuit in case such as you describe would be much less than 0.5 ohm (same as impedance of the equipment grounding conductors).

The 1-5 ohms earthing resistance is the resistance of the grounding electrode to the remote earth and not necessarily part of a ground fault circuit. Unless you do not install any equipment ground conductors, which is a code violation.

Rafiq Bulsara
http://www.srengineersct.com

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