It is currently Fri Aug 12, 2022 1:34 pm



Post new topic Reply to topic

For the secondary of pad mounted transformers do/should you use the ACTUAL GAP or IEEE 1584 gap?
Actual gap distance
IEEE 1584 gaps 0.25 to 1.5 inches
IEEE 1584 gaps between 1.5 and 3 inches
It depends
I don’t perform studies
You may select 1 option

View results
Author Message
ekstra   ara
 Post subject: Pad Mounted Transformer Gap Distance – Actual or IEEE 1584
PostPosted: Sat Jul 09, 2022 11:06 am 
Plasma Level
User avatar

Joined: Mon Sep 17, 2007 5:00 pm
Posts: 1663
Location: Scottsdale, Arizona
The Gap distance affects the arcing short circuit current and ultimately the incident energy. It is understood, that the greater the gap, the more difficult it may be to sustain an arc flash.

The IEEE range of gaps for 208 V to 600 V is: 0.25 in to 3 in (6.35 mm to 76.2 mm)
IEEE 1584 Table 8 suggests gaps of 1 inch (25 mm) to 1.25 inches (32 mm) for low voltage equipment - Panels and Switchgear

However, equipment such as pad mounted transformers can have gap distance significantly greater than those values.

Here is this week’s question:
For the secondary of pad mounted transformers do you use ACTUAL GAP or IEEE 1584 gap?
Actual gap distance
IEEE 1584 gaps 0.25 to 1.5 inches
IEEE 1584 gaps between 1.5 and 3 inches
It depends
I don’t perform studies

Your thoughts are always welcome!


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Pad Mounted Transformer Gap Distance – Actual or IEEE 15
PostPosted: Wed Jul 13, 2022 6:57 am 

Joined: Wed Jul 13, 2022 6:48 am
Posts: 1
Jim Phillips (brainfiller) wrote:
The Gap distance affects the arcing short circuit current and ultimately the incident energy. It is understood, that the greater the gap, the more difficult it may be to sustain an arc flash.

The IEEE range of gaps for 208 V to 600 V is: 0.25 in to 3 in (6.35 mm to 76.2 mm)
IEEE 1584 Table 8 suggests gaps of 1 inch (25 mm) to 1.25 inches (32 mm) for low voltage equipment - Panels and Switchgear

However, equipment such as pad mounted transformers can have gap distance significantly greater than those values.

Here is this week’s question:
For the secondary of pad mounted transformers do you use ACTUAL GAP or IEEE 1584 gap?
Actual gap distance
IEEE 1584 gaps 0.25 to 1.5 inches
IEEE 1584 gaps between 1.5 and 3 inches
It depends
I don’t perform studies

Your thoughts are always welcome!
The problem I have found is that the gap is usually greater than the max suggested by IEEE 1584.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Pad Mounted Transformer Gap Distance – Actual or IEEE 15
PostPosted: Wed Jul 13, 2022 7:58 am 
Arc Level

Joined: Tue Jan 13, 2009 5:00 pm
Posts: 585
I use NESC. (I understand they are redoing the low voltage table for 2023. I haven't seen it yet.)

It occurs to me the initial gap would actually be zero when a worker accidentally brings a grounded conductive object into contact. The gap then widens as the worker pulls away. One of our workers actually did this and singed his eyebrows and ruined his safety glasses and I suspect his underwear. I don't believe the primary fuse cleared and the arc did extinguished once the gap increased sufficiently.

I think using the IEEE gaps makes more sense.


Top
 Profile Send private message  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 3 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:  
© 2022 Arcflash Forum / Brainfiller, Inc. | P.O. Box 12024 | Scottsdale, AZ 85267 USA | 800-874-8883