neutral return current on single-phase system
neutral return current on single-phase system
(OP)
We have a single phase circuit 7200 V to ground in a beach area. The circuit runs 2 or 3 miles and the peak load is around 100 A on the phase. The neutral is multi-grounded.
In looking at the phase amps versus the neutral amps at different points along the circuit, I'm finding we're only getting about 1/3 of the current returning thru the neutral wire. I would have expected more like 1/2 to 1/1 split.
Any ideas?
In looking at the phase amps versus the neutral amps at different points along the circuit, I'm finding we're only getting about 1/3 of the current returning thru the neutral wire. I would have expected more like 1/2 to 1/1 split.
Any ideas?






RE: neutral return current on single-phase system
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: neutral return current on single-phase system
You obviously have other paths being used. Does you local code allow
the water pipes to be used in the grounding system?
100 amps is a lot on a single phase line. I am surprised that you
are not receiving electrical shocking complaints.
RE: neutral return current on single-phase system
Si duri puer ingeni videtur,
preconem facias vel architectum.
RE: neutral return current on single-phase system
And to Bill's comments about using just a single phase wire for our distribution, no, we are using 2 wires.
Homes are fairly new so i wouldn't expect any conductive plumbing in the homes.
One basic question to answer is
- with a long single phase overhead circuit with distributed grounds of 25 ohms, how much neutral return would you expect?
I'm guessing it should be close to 100% of the phase value. That's why I'm looking for other paths.
RE: neutral return current on single-phase system
Good books on this subject include those by Paul Anderson and William Kersting.
It is not too difficult to set up a Matlab/Octave/Freemat etc worksheet to carry out the calculations for your particular situation.
Also, I agree with wareagle, 100 amps is kind of heavy. You may want to look at putting up a second phase and splitting the load.
RE: neutral return current on single-phase system
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: neutral return current on single-phase system
With the grounding aspect, I think it's better to model this as a ladder network where you explicitly represent the neutral-to-earth connections.
I don't think we have a open, but we may have a high resistance connection in te neutral. Good suggestion, Bill.
RE: neutral return current on single-phase system
People in the water were getting shocks when they touched the ladders to get out.
Also,people standing barefoot at the edge of the pool got shocks when they leaned over to touch the water.(Note: all power to this entire pool complex had been turned off when they got these shocks)
It sounds like this could be another situation just waiting to happen.