need some help.

[Monbeast]

what are six reasons we ground and bond?

what is one thing we should always do the same, whether we have a grounded or an ungrounded system?

why do we ground the outdoor utility transformer to a ground electrode and then ground the main service again inside the building to a seperate ground electrode?

on a transformer that is considered a seperately derived system and is located inside the building, do i ground both the transformer to a ground electrode and its disconnect panel to a ground electrode just as we do on the main service transformer and main service panel? why or why not?

 

[iwire]

First off please only post a question once, not six times. :grin:

Next is we try not to just give away answers to students, it works better if you make an attempt at answering the questions and then we can help steer you in the right direction.

Finally you have chosen to ask some pretty deep questions and there will be many opinions about them.

 

[mdshunk]

why do we ground the outdoor utility transformer to a ground electrode and then ground the main service again inside the building to a seperate ground electrode?

For stray current enhancement.

 

[haskindm]

what are six reasons we ground and bond?

what is one thing we should always do the same, whether we have a grounded or an ungrounded system?

See 250.4

Ground the system - see 250.4(A) and (B). Both systems must be connected to earth whether they are grounded or ungrounded.

And they wonder why we get confused.....

 

[charlie b]

Ground the system - see 250.4(A) and (B). Both systems must be connected to earth whether they are grounded or ungrounded. And they wonder why we get confused.....

Not quite true. In both cases, you connect the enclosures to planet Earth. But only for a "grounded system" do you also connect one of the wires to planet Earth (i.e., either the center point of a WYE or perhaps a corner point of a delta).

Does that help clear up at least this point of confusion?

 

[billsnuff]

try here, there are 12 pages by Mike Holt that should answer your questions.

http://ecmweb.com/grounding/

P.S. I recommend his book.