A 120/240 V split phase system is supplied by a center tapped 240 V transformer. The center tap is grounded, deriving the neutral. Unbalanced current from the two hot phase conductors return back through the neutral.
At 08:27 PM 11/25/2016, you wrote:
Wrenches, Is there such a thing as a "grid neutral"? I have been providing design support to a client for a large off grid system; a prepper, rare in these parts. He claims that utility current is carried in part through the ground and in part through a neutral conductor, and such a "utility neutral" is deliberately undersized. At first I pushed back (see below). Now I just wonder what Wrenches more knowledgeable than I am will say. Thank you, Allan Allan Sindelar <mailto:al...@sindelarsolar.com>al...@sindelarsolar.com NABCEP Certified PV Installation Professional NABCEP Certified Technical Sales Professional New Mexico EE98J Journeyman Electrician Founder (Retired), Positive Energy, Inc. 505 780-2738 cell -------- Forwarded Message -------- Date: Thu, 24 Nov 2016 11:25:36 -0700 Allan Happy thanksgiving. Sorry for the slow reply; overwhelmed here. All wet sorry. If you look at the power lines you will see two or three wires at top of pole and the one smaller one a little ways down the pole. This is the power station neutral. The hots bidirectional is an explanation that helps people understand current but is not totally clear. Even if you use that visualization in order for the electrons on the hot to oscillate they heed a path to oscillate into and out of That is the neutral. Bottom line is from the power station and in your home you have at least one hot and one neutral. You can actually use the hot to light up a lite bulb by connecting the other side of the lite bulb to the earth. This one way you can get electrocuted. I touched the hot side of a 220 circuit and the current went thru me and into the earth not much fun. This has been openly publicly discussed and one of the electrical association advised the power companies to increase the size of the neutral to solve many issues, such as cows giving less milk and problems with electric current in homes. The power companies even openly discuss this. In remote rural areas of Australia, I have seen electricity distribution using SWER (Single-Wire Earth Return); just one wire is fed to the property at a high voltage, with the current returning via the ground. At the property, a transformer turns the high voltage into normal residential voltages on a pair of wires (230VAC in Australia vs 2x115V in some other countries). But this SWER system is inefficient, and the supply voltage is poorly regulated; it is a rare exception - it is only done because of the high cost of delivering two wires in remote areas. In metropolitan areas, you will typically see 4 wires passing down the street. This consists of three phases of "Active", plus a "Neutral". You could imagine the Active carrying current "from" the power grid, and the Neutral carrying the current "back to" the power grid (even though the current flow is symmetrical). There is lots of info online if you wish to learn more about this. Take care, Robert From: Allan Sindelar [<mailto:al...@sindelarsolar.com>mailto:al...@sindelarsolar.com] Sent: Sunday, October 23, 2016 10:18 PM Robert, I'm neither an electrical engineer or a utility employee, so I may be all wet here, and if so please dry me off with a straight-up explanation. But this whole argument seems specious to me, as it addresses a "grid neutral". My reasoning is this - there is no such animal as a "grid neutral" in utility lines, so how is this issue even relevant? The "hots" are bidirectional; only when the utility power is stepped down at the transformer at the home is a reference neutral created. To say that the current "cannot all go back thru the neutral since it is not large enough BY DESIGN" seems to me an absurd concept since there is no neutral in utility power distribution. Am I missing something? Allan On 10/2/2016 7:51 PM, Robert wrote: Allan Here is the info I said I would send: <https://www.youtube.com/watch?v=aJOB2FIqUiQ>https://www.youtube.com/watch?v=aJOB2FIqUiQ. Listen about 20 minutes at least. All current that goes out on the two residential or three commercial hots goes back on the grid neutral AND thru the ground'. It cannot all go back thru the neutral since it is not large enough BY DESIGN. So . That means we really dont have a clean ground anymore. Thank you for your time today. It is enjoyable to speak with you. _______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org
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