[AR] Re: extreme igrid interconnection \ Re: Re: Way off topic (was Nitrating C60)
- From: Norman Yarvin <yarvin@xxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Tue, 17 Mar 2015 20:41:50 -0400
On Wed, Mar 18, 2015 at 08:50:39AM +1100, Jake Anderson wrote:
>High voltage DC will do the job of transmission.
>My biggest query with all this is how well will it all deal with a
>decent coronal mass ejection.
That's not actually a problem for HVDC transmission. The problems
come with AC, where transformer cores saturate due to DC that isn't
supposed to be there, but is, because of flux changes through loops in
the grid -- the flux that is changing being the flux of Earth's
magnetic field, and the loops being sometimes hundreds of miles wide.
Even then, the extra current is relatively modest (I've seen numbers
in the tens of amps, for a large event), and the problem is due to
overheating, which takes tens of seconds, and against which there are
automatic safeguards that shut down the transformers (plus people
overseeing the system, who likewise can shut things down if there is a
problem).
So, large-scale blackouts, yes; the end of the world as we know it,
no.
>The voltages and currents induced in a cable that long are going to be
>pretty insane.
With these systems, the voltages are pretty insane even in normal
operation. Except for the core saturation vulnerability, they'd
hardly even notice the disturbance.
Per Wikipedia, the largest known geomagnetic storm (the Carrington
event) resulted in changes in the magnetic field of about 1600
nanotesla. That's as compared to its normal size of 25000 to 65000
nanotesla (depending on location). That's the sort of size of
disturbance (less than a tenth of the normal size) that can be
reasonably expected from shifts in the field (which isn't very strong
to begin with).
Also, it's not the length of the cable that does it; it's the area
enclosed by the loop. A (say) transatlantic transmission cable that
had an associated ground return cable right next to it would have
minimal interaction with the Earth's magnetic field. To make a big
loop, you'd need two transatlantic cables with considerable distance
between them.
In any case, even for the Carrington event, which was in the days of
telegraphs (low voltage in normal operation, and large loops), one
reads of telegraph operators getting shocked, not of them getting
vaporized.
--
Norman Yarvin http://yarchive.net/blog
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