From: moroney@world.std.spaamtrap.com   
      
   On 10/17/2019 2:15 PM, gfretwell@aol.com wrote:   
   > On Thu, 17 Oct 2019 12:10:04 -0400, Michael Moroney   
   >  wrote:   
   >   
   >> On 10/14/2019 4:33 PM, Terry Casey wrote:   
   >>> In article ,   
   >>> gtaylor@tnetconsulting.net says...   
   >>>>   
   >>>> My limited understanding agrees.  The typical home in the U.S. (I don't   
   >>>> know about elsewhere in the world) is feed by a single phase to a   
   >>>> transformer with a center tap that is grounded, and each of side in   
   >>>> relation to the center tap is what I believe is called a "leg".   
   >>>>   
   >>>   
   >>> In Europe, distribution is a 3 phase 4-wire system.   
   >>>   
   >>> Volage in the UK used to be 240V between any phase and neutral   
   >>> and 415V 3-phase.   
   >>>   
   >>> Residential areas are usual connected so that a small number   
   >>> of homes (which could be as low as 1) is fed 240V on a single   
   >>> phase, the next home(s) are fed from a 2nd phase, the next   
   >>> from the 3rd phase and then the sequence repeats. This ensures   
   >>> that the loading on all phases is reasonabl balanced.   
   >>>   
   >>> Heavy industrial users would have 415V 3-phase supplies.   
   >>>   
   >>> Europe had 220V/380V supplies but from 2003, European voltages   
   >>> have been harmonized at 230V/400V although the tolerances on   
   >>> these voltages mean that virtually nothing has changed.   
   >>>   
   >>   
   >> Out of curiosity, what is the typical maximum distance from the   
   >> transformer to the most distant residence?   
   >>   
   >> Here in the US, because of the lower voltage (for most things), they   
   >> usually won't go more than 1 or 2 pole spans before the drop to the   
   >> house, and many newer setups sometimes have a transformer for every   
   >> house. This is for above ground installations, I can't tell about   
   >> underground (most newer neighborhoods) other than how many transformer   
   >> boxes there are along the street.   
   >>   
   > That is not exactly accurate. The single phase delivered to a   
   > residence is nominally 240v (ten higher than most of Europe.)   
   > It just has a center tap dividing that single phase into two 120v   
   > circuits.   
   > If the 120v loads were balanced there would be zero current on the   
   > neutral and you would be computing voltage drop on the 240v circuit.   
   > We actually do that with "multiwire" circuits in the home (AKA shared   
   > neutral/Edison etc).   
   >   
   >   
      
   That may sound good in theory but light blinking is usually seen when a   
   120V motor fed from the same hot as the light is switched on, and draws   
   a starting surge. The drop in the hot is the main culprit, as you   
   mentioned the neutral current is largely canceled.  (I sometimes have   
   seen a "reverse" light blink when a light on the other hot gets brighter   
   when the motor is switched on. This is from a voltage drop in the   
   neutral allowing the hot2-neutral voltage to rise above 120V as the   
   current is out of phase. Rare and requires attention.)   
      
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