It is currently Thu Feb 22, 2018 3:53 am



Post new topic Reply to topic
Author Message
ekstra   ara
 Post subject: Higher IE on CB Load Side
PostPosted: Fri Jan 15, 2010 5:32 am 
Offline
Sparks Level

Joined: Fri May 01, 2009 9:10 am
Posts: 73
Looking at an arc flash study done on a 13.8kV SWGR line up with main breaker. The detailed study shows a significantly higher IE (44.8 cal/cm2) on the load side of some of the breakers than on the SWGR bus (22.8 cal/cm2). These breakers are feeding large motors (5000+HP). Just doesn't seem right. :confused: What, if anything, might cause this?


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Fri Jan 15, 2010 6:48 am 
Offline
Plasma Level

Joined: Mon Jun 02, 2008 11:58 am
Posts: 1103
Location: Charlotte, NC
viper57 wrote:
Looking at an arc flash study done on a 13.8kV SWGR line up with main breaker. The detailed study shows a significantly higher IE (44.8 cal/cm2) on the load side of some of the breakers than on the SWGR bus (22.8 cal/cm2). These breakers are feeding large motors (5000+HP). Just doesn't seem right. :confused: What, if anything, might cause this?


Motor contribution is my guess, hard to tell without all the data. Possiblle you can adjust relay settings to lower this. Sounds like a good canidate for remote racking and switching.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Fri Jan 15, 2010 6:54 am 
Offline
Sparks Level

Joined: Fri May 01, 2009 9:10 am
Posts: 73
How could motor contribution affect the load side and not the line side of the breaker? Could you send me a PM on your company and services offered? Thanks!


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Fri Jan 15, 2010 7:52 am 
Offline
Sparks Level

Joined: Thu Jul 19, 2007 7:54 am
Posts: 201
Location: St. Louis, MO
It's also possible that there is some additional protection on the bus that does not protect the load side equipment, such as differential protection or zone selective interlocking. They may also be taking credit for maintenance settings on the relays at the bus, but not at the motors.

The numbers still seem high on the bus side for this, however. I would look at the study and see if they looked to upstream devices for miscoordination or faster operating times at the arcing fault current levels.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Fri Jan 15, 2010 9:43 am 
Offline
Sparks Level
User avatar

Joined: Sun Aug 16, 2009 8:42 am
Posts: 184
Location: Lawrenceburg KY
Can you post a segment of your one-line that indicates what your speaking of? Sorry, I am a visual type of guy.


Top
 Profile Send private message  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 5 posts ] 

All times are UTC - 7 hours


Who is online

Users browsing this forum: No registered users and 1 guest


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:  
© 2017 Arcflash Forum / Brainfiller, Inc. | P.O. Box 12024 | Scottsdale, AZ 85267 USA | 800-874-8883