# Single phase electrical power from three phase distribution.

• posted

Que: Is it true that in India electrical power is transmitted from 3 phase, Star (Y)- Neutral configured secondary of some power transformer AND any Phase to Star neutral forms the configuration for Single phase-Neutral (P-N) power we receive in our homes? If YES, then (I) Phase is positive with respect to the Neutral during positive half cycle of sine wave. (II) Neutral is positive with respect to the Phase during the negative half cycle of the sine wave. IF THIS NEUTRAL IS EARTHED, THEN HOW DOES THIS POWER FLOW THROUGH THE ELECTRICAL LOAD? It flows through the Earth connection as this has lower impedance than the load, isn'it?

• posted

I can't speak specifically about India, but *generally*, the neutral wire is run with the other phases on the distribution lines. So for a single phase load, it is connected to one phase and to the neutral conductor. The neutral conductor is connected all the way back to the power source, just like the phase conductors.

So the path of 'least resistance' is through the neutral conductor, not into/out of the earth.

The neutral conductor is commonly 'earthed' (connected to a grounding rod) at *many* places throughout the distribution network. But that doesn't mean the majority of load current travels through the earth. Several miles of neutral conductor have a lower resistance than several miles of dirt.

All that being said, there *is* a type of connection that involves just one wire. I've heard of it used in Australia's "outback" and other extremely remote regions where the cost of a second conductor is very high. It is called "Single Wire Earth Return" (SWER). But unless you're in a very remote part of India, I doubt it is in use.

daestrom

• posted

1) Power flow...or more accurately Energy flow is not via the conductors but rather in the EM field between the conductors (and around the conductors). The result of this flow of energy is current in the conductor and a electric field between the conductors.

Look up Poynting vector and then Slepian vector to understand further

2) No power flows through the Load but rather is dissipated by it in the form of heat (usually the losses...unless it's a heater) and usable mechanical movement or illumination (or indeed sound) or some other form.
• posted

The single wire earth return was once common in the Canadian Prairie provinces for rural lines. They were also used in the US in many rural areas. Now, a neutral conductor is also used. There is a story about one Saskatchewan town where the telephone people, whose lines were parallel to some of these rural feeders, complained about possible interference so a neutral was added and brought to ground at the edge of town and not carried onward. No problems. However, the practice of using the single wire may have led to a perceived basis for lawsuits in Wisconsin - "stray currents and cows"

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