Overhead line Ratings
Overhead line Ratings
(OP)
Hi Folks,
I was wondering if anyone could answer the following:-
Flamingo 666.6 mcm overhead line?
1) i am trying to find curves of s/c capacity against tripping time
2) how do i de-rate this cable for warmer climates such as the middle east? also its 2 conductors per phase.
3) short circuit rating of the cable? what formula do i use
i have spent alot of time searching the web with little progress, any help greatly appreciated
many thanks
Flashover (young electrical engineer learning his trade
I was wondering if anyone could answer the following:-
Flamingo 666.6 mcm overhead line?
1) i am trying to find curves of s/c capacity against tripping time
2) how do i de-rate this cable for warmer climates such as the middle east? also its 2 conductors per phase.
3) short circuit rating of the cable? what formula do i use
i have spent alot of time searching the web with little progress, any help greatly appreciated
many thanks
Flashover (young electrical engineer learning his trade






RE: Overhead line Ratings
Also, the s/c capacity against tripping trip - are you looking for the Maximum Fault - Current Operate Curves? also known as cable melt curves - this should be available from the manufacturer.
In that Southwire book there is a whole chapter on Thermal Ratings of Bare Overhead Conductors, with example calc. Also included in that chapter is a section on Fault Current ratings toe determine the adequacy of conductor for s/c currents.
RE: Overhead line Ratings
thanks
flashover
RE: Overhead line Ratings
t = ((0.0862* m)/l)^2 where t = seconds, m = area in circular mils, and l = rms amperes
Upper temperature limit 645 degrees C, ambient temperature 40 degrees C. Time plotted is that required for a given rms fault current to bring aluminum strands to the threshold of melting (steel will be unaffected and will still supply the mechanical strength). It is assumed there is no heat loss in the conductor.
For 666 kcmil Flamingo, this time limit is .33 s @ 100 kA rms and 33 s @ 10 kA rms.
Reference: Aluminum Electrical Conductors Handbook published by the Aluminum Association
RE: Overhead line Ratings
The change in ampacity for a given temperature rise, based on different ambient temperature starting points, is little changed over a considerable range of ambient temperature. Therefore, you should be safe in using standard temperature rise graphs, which are usually based on 40 degree C ambient, even if your ambient temperature is higher.
Of course, other factors have to be considered beside temperature rise, including sun, emissivity, wind conditions, etc.
RE: Overhead line Ratings
If this is a new design, U have a bunch more fun things to figure out.
Summary, there is no easy way to determine what U want. This is a complex problem.
3b2
RE: Overhead line Ratings
thanks Flashover