yukonjack_99674
Member
- Location
- Alaska
Does it matter where you land your neutrals (neutral bar or ground bar) when there is a "High Resistive Ground" system on the main transformer?
Does it matter where you land your neutrals (neutral bar or ground bar) when there is a "High Resistive Ground" system on the main transformer?
Does it matter where you land your neutrals (neutral bar or ground bar) when there is a "High Resistive Ground" system on the main transformer?
The connection and subsequent use of the Xo to a neutral - 4th wire - bus would defeat the purpose and function of the HRG system.
That is a new thought....I see no reason that, with proper design, an HRG system could not function with L-N loads. How does having a neutral circuit conductor defeat an HRG system? As long as it is isolated from ground, it would not prevent continuity of service in the event of a ground fault. ...
As you know, an L-G fault raises the neutral to 277V and the unfaulted lines to 480V above ground. I don't know of any single phase 277 equipment speced to run at the elevated voltage.
I disagree slightly.
Under NEC code, an HRG system is _not permitted_ to serve L-N loads. There are good safety reasons for this, because systems with a neutral are generally designed with the expectation that the neutral will be near ground potential.
However, I see no reason that, with proper design, an HRG system could not function with L-N loads. How does having a neutral circuit conductor defeat an HRG system? As long as it is isolated from ground, it would not prevent continuity of service in the event of a ground fault.
-Jon
I admit that thought did not occur to me today - probably won't tomorrow either.:roll:A L-G fault raises the ground to 277v from the x0 terminal, but the neutral would remain at 0v and single phase loads would be unaffected. Although you would have a potential between neutral and ground of 277v.
It's already difficult to design a relaying system with three phase unbalanced ground fault leakage and account for variations and still be able to determine if it is a fault or not, or to locate the fault. [...]
Let me see if I have this, I have a HRG system on a main transformer. That transformer feeds several other transformers which feed panels and sub-panels. Some of these sub-panels mix their neutrals (white common) with grounds on the same bar. Other panels are separated, neutrals on the neutral bar and grounds on the ground bar.
Nope by golly, I don't have this, lol and I haven't even got to the grounding the X0 on transformers that are down stream of the main transformer. Confused Thanks for everyones help on this, I'm trying to make our system as safe as possible.
The problem I see with HRG with a neutral is detecting a neutral/ground fault.