"The grid" is a vast network of wires and transformers designed to operate
at 60 Hz, the transformers changing the voltage/current ratio as appropriate
for long distance transmission to safe use for households. Transformers are
highly efficient, reliable and durable. DC long haul transmission has been
applied only for a few cases. A broad changeover would be enormously costly.
Current practice is thanve local feeds down the street at a few kilovolts
with pole transformers every block or so to convert to house uasge.
Curiously, this system uses an earth return on the high voltage side of the
transformer. With a good grounding rod, the earth resistance is about 50
ohms, I think. Although somwhat lossy, it is cheaper than running more
copper to the transformers.
Switching power supply technology is now mature and commonplace, even in
compact fluorescent lamps. in principle, a DC system could now be built, but
as good as solid state is, it is hard to beat iron and copper for durability
and efficiency.
Mike Carrell
----- Original Message -----
From: "Michel Jullian" <[EMAIL PROTECTED]>
To: <vortex-l@eskimo.com>
Sent: Wednesday, March 26, 2008 5:23 PM
Subject: [Vo]:Re: Emergency Electric Curtailment event in Texas / more bull
from Lutz
Is there anything in the grid proper (i.e. excluding converters at supply
and receiving ends) that makes it inherently AC? If not, it would make sense
to convert the whole system to DC, if only because root(2) more rms voltage
would be allowed, i.e. 57% more power could be carried by the same lines for
the same allowed current i.e. the same allowed ohmic losses.
Michel
----- Original Message -----
From: "Robin van Spaandonk" <[EMAIL PROTECTED]>
To: <vortex-l@eskimo.com>
Sent: Wednesday, March 26, 2008 9:30 PM
Subject: Re: [Vo]:Emergency Electric Curtailment event in Texas / more bull
from Lutz
In reply to Mike Carrell's message of Wed, 26 Mar 2008 09:48:25 -0400:
Hi,
[snip]
What is fundamentally different is that in the conventional system, the AC
rotating machines are locked in synchronism with the 60 Hz grid, and if any
one falls out of synch, destruction will follow. With wind turbines this
need not happen.
[snip]
If the national grid were DC iso AC, then synchronization problems would be
inherently non-existent. Any form of power source could contribute, with
conversion from AC to DC taking place locally on the supply end, and
conversion
from DC to AC taking place at substations on the receiving end. It would
also
have the advantage of more efficient long distance transport.
Of course, it would no longer provide 60 Hz synchronization of clocks, but
this
is easily overcome by allowing the substations to use crystal controlled
oscillators, synchronized via the Internet.
Regards,
Robin van Spaandonk
The shrub is a plant.
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