×
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

6.9 KV Fault
2

6.9 KV Fault

6.9 KV Fault

(OP)
I have a project supporting cable trays and I understand that it is possible for a fault to cause the cables to 'whip' around.  Does anyone have an idea of the magnitude of the force generated by the 'whipping' motion?

thanks, Dik

RE: 6.9 KV Fault

For single core cables you do get substantial magnetic forces between the cables under fault conditions. The force on the cables is proportional to the square of the fault current, and inversely proportional to the spacing. For single core cables laid in trefoil EN50368 gives the formula F= (0.17x Isqd)/S. F is the force in Nm, S is the cable diameter in m, I is the peak short circuit current in kA.
You could use this formula to specify the cable cleats and cleat spacing.
This formula gives the static load instantaneously created by the short circuit, however the phase changes
of the alternating current mean that the forces on the cable and their direction are changing continuously.
No simple formula and no static test can assess the effect of these dynamic forces. The ultimate proof of any
cable fixing system to withstand a short-circuit is to undertake a short-circuit test.
Regards
Marmite

RE: 6.9 KV Fault

(OP)
Thanks, gentlemen... Dik

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