×
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

Cable Data & x/r ratio

Cable Data & x/r ratio

Cable Data & x/r ratio

(OP)
Cable Data:

Can someone tell me where to get 'reputable' copper cable impedance data. I know that cable impedance depends on many factors (spacing, insulation, shielding,configuration, construction). Is there a way that the above paramaters can be incorporated into a formula to figure out the cable impedance?

X/R Ratio:

Is there a standard procedure for what to do when you when you've been given the short circuit current at a stack, and a load on the end of a downstream cable, but no X/R ratio for the available short circuit upstream.

I've heard that you can use the X/R ratio of the transformer...but unfortuantely I have no even been given that data. All I konw is that the stack has a given SC current and that it feeds three other downstream stacks which are a combined load of 333 kVA?

Any suggestions at all on this one?

RE: Cable Data & x/r ratio

My suggestion is to get a good reference book on calculation of short circuit currents.  The IEEE Red Book is a good starting point.  Textbooks by Stevenson and Paul Anderson are a good resource.

If you're dealing with industrial systems, I'd recommend "A Practical Guide to Short Circuit Currents" by Conrad St. Pierre.

The cable impedance calculations can be somewhat complicated if you're looking for a high degree of precision.  The resistance is also temperature dependent, so any perceived accuracy in your reactance data must be tempered with the fact that you almost never know the actual conductor in the conductor and it is generally not uniform.  

Transformer X/R ratio can be calculated if you know the %Z and the losses.  Or you can use approximate value from Red Book for similar size units.  

RE: Cable Data & x/r ratio

Correction - should have said "you almost never know the actual conductor **temperature** in the conductor....

Glad it's Friday....

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