Ground Fault

Status
Not open for further replies.
C

Cody K

Senior Member
Location
Texas
I have read the previous topic on grounding in this forum... and then all of the informative attachments relating to the importance of equipment bonding to the neutral conductor to create a low resistance path to the source (utility transformers)

My question is... how do you bond parts to create a low resistance path to source on a 3 wire, three phase, 480Y/277 system which my company utilizes (there is no nuetral). thanks
 
Cody K said:
I have read the previous topic on grounding in this forum... and then all of the informative attachments relating to the importance of equipment bonding to the neutral conductor to create a low resistance path to the source (utility transformers)

My question is... how do you bond parts to create a low resistance path to source on a 3 wire, three phase, 480Y/277 system which my company utilizes (there is no nuetral). thanks
Click to expand...


The system you mentioned is a 4 wire system which has a neutral. A 480 volt 3 wire Delta system can have one of the phases grounded to create a grounded conductor. Or the system can operate as an ungrounded system with certain restrictions.
 
Your right. Now that I think about it the Y is grounded at the transformer bank. However the service enters our system at the disconnect with three ungrounded conductors only. We usually ground at this disconnect with an electrode, but that means we are depending on the earth for the return path to ground which seems to be a bad idea (higher resistance to source thru ground).
 
You should have a grounded conductor brought to the service disconnect. Look at 250.24(C).
 
No, according to Cody's second post, the transformer is grounded. If that is the case, then 250.24(C) would require a grounded conductor to be brought in with the service conductors. They wouldn't be able to use an ungrounded system, because it is grounded at some point.
 
Status
Not open for further replies.
Top