On 03/14/2015 07:32 PM, Lennart Sorensen wrote:
Well I suppose that with the main distribution being 3 phase power, but only running 2 phase power in residential areas (which I believe is generated by transformers from just 1 of the 3 phases in the main distribution, called I believe split phase, using a centre tap to ground to give the 2 phases, 180 degrees apart), does result in a potentially quite unbalanced grid, where the 3 phases could get rather out of balance. I have no idea if this really results in a big load imballance problem in general, or not.
Yes, residential distribution is just a single phase, center tapped. While only one phase is used in an area, other phases will be used elsewhere with the loads approximately balanced. In fact, in some areas, 3 phase is run at high voltage, with the distribution transformers, along the line, connected across different phases The centre tap results in the phases being 180° apart at the customer. The advantage of this is the neutral current will be the difference of that in the two "hot" lines.