single line to ground fault 1

[sahelrahman]

While doing the arc flash study, I wonder what effect does the single line to ground fault has on arc flash current and incident energy?

When I performed the arc flash study, I did a mistake of low resistance grounding the transformer and generator instead of solidly grounding them. There was no effect on 3phase current. But single line to ground fault current changed drastically when I changed the grounding to solid. What effect does that have on arc flash?

 

[magoo2]

duuh!

 

[davidbeach]

None what so ever.

 

[cranky108]

Depends. If you never have a fault, then all this arc-flash stuff hasen't helped you.

 

[dpc]

The IEEE 1584 method for arc-flash calculations is based entirely on three-phase faults on three-phase systems. This generally going to be the worst-case, so line to ground faults don't enter into the picture.



David Castor

http://www.cvoes.com

 

[sahelrahman]

Thanks everyone!!
Hi dpc...
I am using NFPA calculation. So is it going to change the arc flash. If not, why are we doing the single line to fault calculation?

 

[dpc]

Same approach - three-phase faults only.



David Castor

http://www.cvoes.com

 

[jghrist]

You may need single line-to-ground faults for coordination, but not for arc flash.

 

[azamfaez77]

As far as I know, 3 phase fault current calculation is overcurrent relay setting.Meanwhile single phase fault is earth fault relay setting.

Correct me if i wrong.