It is currently Mon Mar 01, 2021 1:06 pm



Post new topic Reply to topic
Author Message
ekstra   ara
 Post subject: Insulating barriers installed between electrodes
PostPosted: Fri Jan 22, 2021 9:02 am 

Joined: Fri Jan 22, 2021 7:53 am
Posts: 1
Hi everyone.

Some of the equipment we need to complete arc flash studies for have vertical insulating barriers installed between each phase (for example - 12.47kV-600/347V live front padmounted transformers [photos attached] and 15kV outdoor metal enclosed switchgear). My question is, in these cases, should we be considering the direct electrode to electrode gap as if the glastic barriers were not in place or should we be considering the electrode gap to be the shortest distance between electrode taking the path around the glastic barriers?

I have tried doing a good amount of research but cannot find anything discussing one way or the other. I've found many articles which mention insulating barriers holding up quite well, being charred but not burned through during arc flash incidents, but have also found a source stating the resin in glastic barriers melts as low as 232degC (450degF). The one concern I see with considering the longer path is that it will almost certainly exceed the IEEE 1584-18 maximum bus gaps, resulting in needing to use the less favorable/ accurate Ralph-Lee method (Milsoft, online calculators, and the IEEE spreadsheet will not perform the analysis if the parameters are outside of the IEEE 1584 bounds).

If anyone could provide their thoughts or experiences, it would be greatly appreciated.

Thanks!

Serge


You do not have the required permissions to view the files attached to this post.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Insulating barriers installed between electrodes
PostPosted: Mon Jan 25, 2021 6:43 am 
Plasma Level
User avatar

Joined: Mon Sep 17, 2007 5:00 pm
Posts: 1561
Location: Scottsdale, Arizona
As you found, there is still limited information for every arc flash situation. IEEE 1584 assumes there are no barriers between the bus.

Many would assume "worst case" with no barrier with the reasoning, what if it was removed, damaged, melted - basically some justification for calculating a straight line between the buses. Could that happen? Who knows but when legal minds get involved....

Others may have different views, but this is a pretty common one.

How does it affect the incident energy? Remember in the end it is all about making sure the worker is protected from the arc flash should there be energized work (which it to be avoided unless justified based on NFPA 70E)
Do the different assumptions result in higher arc ratings for PPE?


Top
 Profile Send private message  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 2 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