CR4® - The Engineer's Place for News and Discussion®


Previous in Forum: Capacitance and Tan Delta Measurements   Next in Forum: Clarification Sought on Operating Sequence of a Circuit Breaker
Close
Close
Close
3 comments
Member

Join Date: Feb 2014
Posts: 6

Ampacity of Cu 15kV Cable in Covered Cable Tray - Triplex Single Conductor

12/02/2017 4:14 PM

Hi,

In NEC 2011 Section 392.80(B)(2) there does not seem to be a table for the following condition:

-MV-90 copper cable larger than 1/0 AWG higher than 2001 VAC

-in covered ventilated (flat louver) cable tray

- single conductor, triplexed arrangement

In the absence of the above condition, does table 310.60(C)(67) apply?

I am determining the ampacity or derated ampacity for a MV-90, 15kV, Cu cable, single conductor. Triplex arrangement is preferred in a covered cable tray.

Any help is welcome.

Tito

Register to Reply
Pathfinder Tags: 15kv cable amapacity nec
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Guru
Engineering Fields - Power Engineering - New Member

Join Date: May 2007
Location: NYC metropolitan area.
Posts: 3007
Good Answers: 421
#1

Re: Ampacity of Cu 15kV cable in covered cable tray - triplex single conductor

12/02/2017 7:44 PM

Your best bet is to contact the manufacturer of the particular cable that you are using. There are a number of factors that go into derating the cable from its free-air ampacity, including such things as the ambient conditions, tray orientation/material, covered/vented, distance from/proximity to other conductors and their arrangement, etc., etc. Most manufacturers also offer handbooks and catalogs that cover these and other ampacity considerations.

__________________
Curious minds want to know, engineering minds get answers....
Register to Reply Score 1 for Good Answer
Guru

Join Date: Oct 2012
Location: 100 miles North from the World Center
Posts: 757
Good Answers: 31
#2

Re: Ampacity of Cu 15kV Cable in Covered Cable Tray - Triplex Single Conductor

12/03/2017 10:45 AM

Usually the raised cover purpose it is to protect the cables from the sun radiation. NEC does not deal with sun radiation.

This system is common for power station outdoor cable tray.

Here the NEC recommendations are not compulsory.

So a special calculation was developed.

The calculation is based on thermodynamics-heat produced in the conductor when current flows through it and heat evacuation by radiation and convection to the environmental air.

__________________
Julius
Register to Reply Score 1 for Good Answer
Guru
New Zealand - Member - Kiwi Popular Science - Weaponology - New Member Engineering Fields - Power Engineering - New Member Engineering Fields - Electrical Engineering - New Member

Join Date: Sep 2006
Location: Auckland, New Zealand
Posts: 8494
Good Answers: 351
#3

Re: Ampacity of Cu 15kV Cable in Covered Cable Tray - Triplex Single Conductor

12/03/2017 1:59 PM

Yep, check out the cable manufacturers website for the cable datasheet and/or application notes (or possibly the product line guide catalogue or similar).

Generally (in one of these documents) they will have the particular de-rating factors relevant for the cable, cable configuration and cable tray.

__________________
jack of all trades
Register to Reply
Register to Reply 3 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Copy to Clipboard

Users who posted comments:

7anoter4 (1); jack of all trades (1); RAMConsult (1)

Previous in Forum: Capacitance and Tan Delta Measurements   Next in Forum: Clarification Sought on Operating Sequence of a Circuit Breaker

Advertisement