patrick.net

Guys, I have not been reading this thread yesterday, but take it from an EE with quite a few years of additional education on top of the basic degree (if you catch my drift):

There has been a few misleading and/or errant statements made about certain electrical topics in this thread yesterday. I'm not quite in the mood to dissect all of it, but let me just clarify one or two points.

First, I should caution that there are many different ways of saying the same thing here, but let me just try to say it one way and see if that makes sense to everyone.

The reason that high voltage in a transmission system does not translate into hot and melting wires is that the VOLTAGE DROP along the wire is quite small. Note that there is a difference between the voltage drop along the wire and the voltage drop across the load that is connected between the two (or more) wires. The voltage drop across the load does (mostly) productive work. The voltage drop along the wire is plain loss.

More detail:

The reason that high voltage transmission is more efficient is that lower current is required to transmit tghe same power (P=V*I, V goes up, I goes down, for constant P). The loss in the wire is P(loss)=I^2*R, with a lower I than before.

Of course, there is more to the story than this, because there also are losses in the insulating medium (or "dielectric") between the wires (air, rubber, oil in transformers, etc etc). At some point, diminishing returns are going to set in when you increase the voltage, because the insulation gets prohibitive, the wires have to be spaced too far apart, etc etc etc.

Now, as I had mentioned a few months ago, one of the reason that DC transmission systems can be more efficient than AC , is that dielectric losses tend to be lower when there is a constant electric field rather than an alternating electric field. The latter is jerking the bound electrons in the insulator around quite a bit, and energy is lost. This is all a bit folksy a way of saying it, but you get the idea.

I agree with Fuzzy about current density. It is just an alternative way of saying the same thing as I just did. And I will defer to Neutron on most things nuclear :-).

Oh, I did not see Neutron's 1:35 am post. Also correct.

Duke,

I can agree that discussion of energy and energy conversion systems is a bit OT, but it sure has a profound effect on the economy in general and housing matters as well.

I think those exchanges are very worthwhile.

Duke,

Yeah, congratulations to Krugman, one of many decent economists that have advocated buying preferred equity rather than buying bad assets.

Duke Says:
Can we start a new thread?

It's up.