Newsgroups: sci.electronics.misc
Subject: Re: Does the earth "complete the circuit" to become ground?
References:  <[email protected]>  <[email protected]>  <[email protected]> 
"Thomas G. Marshall"  writes:
> 
> What exactly is it on those "high voltage lines" that you see everywhere.
> Not the telephone poles, but the "high tension" power lines that ride very
> high up and cut huge swaths through forests.  There are often two lines,
> IIRC.  Is that one power and one return?  Or are they both hot, just out of
> phase----though you did mention 3 120 degree phase shifted
> lines......interesting.

The practices how "high voltage lines" vary somewhat from country to country. 
The two wire "high voltage lines" consist generally of phase and neutral 
wires. You can think them as power feed and return wires. 

There are "high voltage lines" that have three wires. 
Those are used to transport three-phase power (three 120 degree phase shifted
lnes) without neutral. 

The very high voltage lines that transport lots of electrical 
power tend to be three-phase systems because it is better 
for energy transport (less losses per transported kW is 
a good reason, and they have also other good properties). 
Three phase wiring is the norm when voltages are from tens 
of kilovolts to several hundred kilovolts. 
And three-phase is also used on many countries widely 
at lower voltages (three-phase power is common in many 
European countries). 

Single phase two wire "high voltage" power distribution is 
often seen in the USA in the lines that feed the power to 
the distribution transformers that feed that 110V / 220V 
power to the building. The voltage on those lines is generally 
several kilovolts. 

-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/