Arc Flash

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anbm

Senior Member
Does anyone has any experiences how to select different type of fuse for CB that can help to reduce arc flash current at main service swbd (480V)? Or methods of how to reduce arc flash? Thank you!
 

zog

Senior Member
Location
Charlotte, NC
Does anyone has any experiences how to select different type of fuse for CB that can help to reduce arc flash current at main service swbd (480V)? Or methods of how to reduce arc flash? Thank you!

Do it everyday, keep in mind recucing your fault current can often result in higher Ei's. What type of breaker is your main and what trip unit does it have (Including functions)?
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Does anyone has any experiences how to select different type of fuse for CB that can help to reduce arc flash current at main service swbd (480V)? Or methods of how to reduce arc flash? Thank you!
It depends on what type of equipment you are dealing with.

In general the arc flash incident energy at the service equipment, itself, can not be reduced as the only upstream protective device is belongs to the utility. For switchboard style equipment (i.e. molded case breakers and 600V max fuses) you can look into adding a remote main to move the higher AFIE to a 'less interfaced with' location.
 

anbm

Senior Member
we had bolt pressure switch with fuse in main switchboard - 480V/3PH, the calculated ncident energy level at this swbd is around 140ca/cm*cm
 

zog

Senior Member
Location
Charlotte, NC
we had bolt pressure switch with fuse in main switchboard - 480V/3PH, the calculated ncident energy level at this swbd is around 140ca/cm*cm

As Jim mentioned that will be hard to mitigate, remote switching may be your best option.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
we had bolt pressure switch with fuse in main switchboard - 480V/3PH, the calculated ncident energy level at this swbd is around 140ca/cm*cm
Part of the problem is that no protective device can protect itself. You need to have some type of coordinated protection upstream from this switchboard and it is unlikely the utility will provide it.

I would investigate adding a new remote mounted main service entrance device between the utility and your existing equipment.
 

anbm

Senior Member
Can we leave it alone and still okay with code? Once we want to service the switchboard, ask utility to de-energy power to the swbd?
 

spikes2020

Member
Location
Nashville, TN
Can we leave it alone and still okay with code? Once we want to service the switchboard, ask utility to de-energy power to the swbd?

They usually have a charge to come out and do that, between 200 and 500 dollars. I am assuming that your building some main fuse on the pole. But it's still required to have an Arc Flash Sticker just make the policy not to work on it while the power is on....

then you wont need the equipment.....
 

anbm

Senior Member
They usually have a charge to come out and do that, between 200 and 500 dollars. I am assuming that your building some main fuse on the pole. But it's still required to have an Arc Flash Sticker just make the policy not to work on it while the power is on....

then you wont need the equipment.....


NFPA-70E --> There won't be a defined arc flash label when the incident level greater than 40cal/cm*cm
 

ron

Senior Member
Can we leave it alone and still okay with code? Once we want to service the switchboard, ask utility to de-energy power to the swbd?

This is a good attempt at a solution. The practical nature is, that even when the utility de-energizes, you still need to wear the proper PPE at your SWBD to verify that it is de-energized per NFPA 70E before you work on it. Of course there is none.
 
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