Cable Size Selection

I am curious about how to determine the cross section of a three phase power cable including the length; for example if I know my length, how can I calculate the cross section of my power cable?


asked 9/12/2012
Shala Yousu2
Shala Yousu

1 Answer

I think you're asking how to determine what size of power cable you should use.

To size a power cable you need to know:

  1. The load being supplied (i.e. 50 amp, 440V 3-phase load)
  2. The length of the cable (i.e. 100m)
  3. The permissible voltage drop from one end of the cable to the other (i.e. 2%)
  4. The short circuit current the cable is required to withstand


You select the cable size so that the following three criteria are satisfied:

  1. Current carrying capacity - the cable can continuously carry the maximum demand current without overheating.
  2. Voltage drop - the cable resistance (ohms/km) does not result in excessive voltage drop at full current.
  3. Short circuit withstand - the cable can withstand the maximum prospective fault current until a protective device operates. (If the closes protective device could fail to operate, use the operating time of the next backup protection device.)


In Australian practice this entire procedure is explained, with examples, in the cable selection standard AS3008.1:2009, Electrical Installations - Selection of Cables - Part 1: Cables for alternating voltages up to and including 0.6/1kV.

answered 12/3/2012 Li-aung Yip 3
Li-aung Yip

Your Answer

In order to provide an answer to this question, you must Login

I am flagging this question because...




10 inform moderator flags remaining

I am deleting this question because...




I am flagging this answer because...




10 inform moderator flags remaining

Flagging a Post

You have already flagged this post. Clicking "Remove Flag" below will remove your flag, thus reducing the count by one as well.

I am deleting this answer because...





Latest Questions:

  1. How many motors, or of what kind, do I need to get the output to be 5 Volts under load?
  2. Three winding transformer impedance
  3. Short Circuit Fault Current (comprehensive)
  4. help for electricity distribution (HTA) through underground cables (6 circuits)
  5. CT Secondary Rating
  6. Embedded system design
  7. PV system design - advice
  8. Power consumption of motor during starting

most popular notesMost Popular Notes:







newsletter logo

Our Newsletter

Receive updates on new posts by email
down arrow

Our website uses cookies so that we can provide a better experience.
To learn more about what cookies are and how to manage them visit AboutCookies.org