P
Phil Allison
Guest
"Puppet_Sock"
The situation where DC transmission is better is where the
transmission line is long compared to a 1/4 wavelength of
the AC transmission frequency. The typical transmission is
60 cps. So 3E8 m/s divided by 60/s, then divided by 4, is
1,250 km. So when you get transmission distances in
that range, radiative loss starts to be significant, and it
gets tough to match the impedance of the line to the load.
Basically what you get is a very large dipole antenna.
Anyway, long distance transmission is sometimes done
on DC lines to reduce radiative loss.
** I think this is entirely false.
There is no comparison with a 60 Hz dipole antenna.
AC power transmission is done with 3-phases ( spaced by exactly 120
degrees ) running a few metres apart, all in exact parallel across the
country - so the net 60Hz eclectic field at a distance always cancels to
ZERO !!.
Ergo, there simply is no "radiation loss" .
The real losses encountered are due to resistive heating, voltage drop and
phase angle changes on very long lines.
http://en.wikipedia.org/wiki/Electric_power_transmission#Limitations
...... Phil
The situation where DC transmission is better is where the
transmission line is long compared to a 1/4 wavelength of
the AC transmission frequency. The typical transmission is
60 cps. So 3E8 m/s divided by 60/s, then divided by 4, is
1,250 km. So when you get transmission distances in
that range, radiative loss starts to be significant, and it
gets tough to match the impedance of the line to the load.
Basically what you get is a very large dipole antenna.
Anyway, long distance transmission is sometimes done
on DC lines to reduce radiative loss.
** I think this is entirely false.
There is no comparison with a 60 Hz dipole antenna.
AC power transmission is done with 3-phases ( spaced by exactly 120
degrees ) running a few metres apart, all in exact parallel across the
country - so the net 60Hz eclectic field at a distance always cancels to
ZERO !!.
Ergo, there simply is no "radiation loss" .
The real losses encountered are due to resistive heating, voltage drop and
phase angle changes on very long lines.
http://en.wikipedia.org/wiki/Electric_power_transmission#Limitations
...... Phil