×
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

Transmission conductor midspan phase - phase clearance

Transmission conductor midspan phase - phase clearance

Transmission conductor midspan phase - phase clearance

(OP)
The NESC does not specifically address ph - ph clearance so I have a two part question:
what criteria are people using to determine ph - ph midspan clearance?
What will happen if the phases get too close?  Is there a potential for issues with induction?

Thanks,

-Ethan

RE: Transmission conductor midspan phase - phase clearance

If they get too close, they could flash over.  Additionally, they are more likely to physically contact from things like wind, nearby car vs pole accidents, fault current flowing through to a remote location or differential ice loading.

One other factor to consider is construction consistency. In vertical construction, just a small difference in tension between two phases can result in a pretty significant difference in sag.

What do you mean by induction?  Changing the phase to phase clearances would change the impedance of the line, but that is different from a three phase power line causing induction in some other nearby cable.

In some instances, we scale up the clearance listed for distribution voltages for our transmission system.  In others, it is based on standard lattice tower designs.  In long span crossing applications, each one is evaluated separately.

Utility is areas with raptor problems sometimes have phase to phase spacing large enough to prevent the birds from touching two phases at once.

Mark

RE: Transmission conductor midspan phase - phase clearance

The RUS Transmission Design Guide Bulleting 1724E has an equation for recommended horizontal separation relative to sag.

Another consideration is conductor galloping if you are in an area that has icing.
 

RE: Transmission conductor midspan phase - phase clearance

You may be able to adequate rule NESC 235 to phase to phase clearance

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