×
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

Voltage Drop for 2400V system

Voltage Drop for 2400V system

Voltage Drop for 2400V system

(OP)
Dear All,

I am new to this forum and I have one question here. During our design for an airport ILS project, I find I need to calculate the voltage drop for a cable between the step-up and step-down transformer. It's about 3,170ft long and is the load is about 12amp at 2400V. My problem is that NEC Table 9 only provides cable information at 600V. How can I obtain cable info for 2400V?

Your help is highly appreciated and if there is anything wrong with my first post, just let me know.

James

RE: Voltage Drop for 2400V system

An ohm is an ohm and an amp is an amp.  Voltage drop in a function of amp-feet (or amp-meters) through a given impedance.

RE: Voltage Drop for 2400V system

As davidbeach sez, just do the per foot thing.

RE: Voltage Drop for 2400V system

(OP)
Thanks, davidbeach and itsmoked. But can I use the table value for 600V cable to calculate impedance of 2.4kv cable?

RE: Voltage Drop for 2400V system

Cable manufacturer publishes impedance values or charts for MV cables. Contact Okonite, Kerite or Pirelli etc.

RE: Voltage Drop for 2400V system

JCHENNI:

Contact the cable manufacturer and obtain the data from them.

Either:
the approx. impedance / given distance (ohm/km, ohm/mile, etc.)
or
the voltage drop per amp metre (or feet)

Failure seldom stops us, it is the fear for failure that stops us - Jack Lemmon

Make the best use of Eng-Tips.com
Read the Site Policies at FAQ731-376

RE: Voltage Drop for 2400V system

Impedance depends on the type of cable (shielded vs. non-shielded) and physical arrangment. I agree with Ralph. The manufacturer should have impedance tables for typical installations.

Is this a series lighting circuit? Airfield systems are commonly series connected circuits, fed by a constant current transformer. In that case voltage drop may not be a significant to the design.

RE: Voltage Drop for 2400V system

The resistance of #2 cu = .194 per 1000 ft and #2 AL = .319
per 1000 ft. An estimate of the voltage drop is

#2Cu .194 x 3.170 x 12 = 7.4 volts  and for
#2al .319 x 3.174 x 12 = 12.1 volts.




RE: Voltage Drop for 2400V system

A rough rule of thumb- One mile per 1 KV.
2.4 KV 2-1/2 miles.
YMMV depending on load.

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