It is currently Mon Mar 30, 2020 12:05 pm



Post new topic Reply to topic
Author Message
ekstra   ara
 Post subject: Cable-Tray & Walkway
PostPosted: Mon Sep 20, 2010 2:14 pm 

Joined: Wed Nov 12, 2008 10:26 am
Posts: 46
Location: CA
A horizontal ladder type cable-tray runs parallel to a pedestrian walkway, which is about ten feet way. The cable tray carries cables from an outside 750kVA transformer to indoor 208v switchgear. The AF IE value on the load side of the transformer secondary (208v) CB is 90 cal/cm^2, which implies a 21 ft Flash Protection Boundary for the cable-tray.

Does this imply that the walkway should be closed?

How would you handle this?


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Mon Sep 20, 2010 4:52 pm 
Plasma Level

Joined: Mon Jun 02, 2008 11:58 am
Posts: 1103
Location: Charlotte, NC
ZeroSeq wrote:
A horizontal ladder type cable-tray runs parallel to a pedestrian walkway, which is about ten feet way. The cable tray carries cables from an outside 750kVA transformer to indoor 208v switchgear. The AF IE value on the load side of the transformer secondary (208v) CB is 90 cal/cm^2, which implies a 21 ft Flash Protection Boundary for the cable-tray.

Does this imply that the walkway should be closed?

How would you handle this?


The arc flash boundary only applies when someone is "interacting" with the equipment. However, there is always a risk of cable failure.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Mon Dec 06, 2010 9:12 pm 
Sparks Level

Joined: Mon Mar 29, 2010 5:02 am
Posts: 136
Hazzard vs Risk....

Is there a risk of it failing and what is the probability of it?

Is there a risk of the transformer in your alley/yard failing and exploding? Do you avoid using that area of your yard?


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Tue Dec 07, 2010 8:26 am 
Sparks Level
User avatar

Joined: Tue Oct 26, 2010 5:00 pm
Posts: 184
Location: Maple Valley, WA.
If there is no exposed energized parts, and you are not interacting with the cables, then there should not be an AF Hazard risk. I would not be concerned about the remote chance or risk of a cable failure. This is not a known predictable failure.

_________________
Robert Fuhr, P.E.; P.Eng.
PowerStudies


Top
 Profile Send private message  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 4 posts ] 

All times are UTC - 7 hours


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
© 2019 Arcflash Forum / Brainfiller, Inc. | P.O. Box 12024 | Scottsdale, AZ 85267 USA | 800-874-8883