...stabilize the voltage to earth during normal operation...

Status
Not open for further replies.

mark32

Senior Member
Location
Currently in NJ
I've read most of the posts here dedicated to the title of this thread, but can't seem to completly understand it in theory. Let's take a typical residential dwelling and wire it as you normally would except you do not make any connections to any grounding electrodes. Now, during normal operation, how would this system behave? Would it experience odd voltage readings? What dangers could result during normal operation?
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Let's take a typical residential dwelling and wire it as you normally would except you do not make any connections to any grounding electrodes. Now, during normal operation, how would this system behave?
I would expect it to behave as any sub-panel with a separate EGC, such as in a detached building. The neutral is isolated from any grounded surfaces or objects, and one would expect the line-to-neutral voltages to measure as usual: near zero.

Any voltage between the isolated neutral and any ground would be generated by either voltage drop on the neutral, or by voltage gradients from a current being injected into the earth by an outside source, such as a neighbor's open neutral.
 

bphgravity

Senior Member
Location
Florida
That exact statement, "stabilize voltage to earth during normal operation", dates all the way back to telegraphy days. It made more sense then and was of greater importance, especially when trying to troubleshoot a bad circuit. This statement existed when the system included the source. That is, the supply was not independent, but a component of the entire system. Today, the utility service provider grounds their systems, so we must to be default on the premise wiring side since there will ALWAYS be a potential (path back to the source) from any ungrounded conductor to earth on a modern day system.

Think of it this way. The source limits and regulates the voltage between any two ungrounded conductors. On a grounded system (one conductor intentionally connected to earth), the voltage between any ungrounded conductor and any non-current carrying metal part properly bonded and/or connected via a EGC, OR the earth, OR a body that serves in place of the earth, the voltage will be the same at any point (save for voltage drop). However, on a system where no connection is made to earth at ANY point (even at the source), the voltage between the ungrounded conductors and metal parts, the earht, etc. can be from zero to infinite. This would be considered unstable.
 
Status
Not open for further replies.
Top