More california insanity

[jamesqf]

Originally Posted by H-Man

May seem like sorcery, but that just explains why every electrical engineer I've ever seen has a beard.

My former co-workers, electric power systems engineers Heidi, Gail, Carolyn, and Karen, would strongly object to that stereotype :-)

[oil pan 4]

High voltage DC lines are typically over head.
Capacitance is why all long distance lines are above ground. If they were under ground the wire insulation would absorb so much energy on a 750kv, 60Hz system that only after 25 or 26 miles no power would make it to the other side of the line. The lines capacitance would equal the transmission capacity at that distance.
Brazil currently has the longest DC transmission line. Something like 600 to 700 miles with almost no line loss.
The old solution was to use 25Hz for long distance transmission and rotary convert it back to 60Hz. But with better cheaper faster electronics converting very high voltage DC back to AC isn't a challenge like it was 30 or 40 years ago.

Originally Posted by UFO

It's not necessary to move power that distance.

You are correct, there should be no need to move power that distance, but when a (failed) government refuses to build power plants within a very large state, voilà stupidity prevails and demand is created for that which defies logic.

[UFO]

Originally Posted by NeilBlanchard

No, actually very high voltage DC transmission lines are more efficient than AC.

Only because you can use thicker cables and only for very long distances. You are failing to account for all the losses, specifically boosting and bucking to the high voltage. This is also apparently only worth implementing for transmission distances of more than a thousand miles, which is unnecessary to do since generating stations are much closer than that to their loads. And one must also bury these cables since they are so heavy the towers cannot support the weight. Does not sound feasible to me.

[UFO]

Originally Posted by jamesqf

My former co-workers, electric power systems engineers Heidi, Gail, Carolyn, and Karen, would strongly object to that stereotype :-)

Indeed. So do I. It's not magic.

[jamesqf]

Originally Posted by oil pan 4

Brazil currently has the longest DC transmission line. Something like 600 to 700 miles with almost no line loss.

Not true. The Pacific DC Intertie is about 850 miles, from Celilo near Bonneville Dam on the Columbia River, to the Sylmar converter station in the LA Basin. There are even longer ones - 1200-1400 miles - in other countries.

You are correct, there should be no need to move power that distance, but when a (failed) government refuses to build power plants within a very large state, voilà stupidity prevails and demand is created for that which defies logic.

Sorry, but you're wrong here. There's a very good economic case for long-distance transmission, as for instance with the above DC intertie. You have dams (and now wind farms) on the Columbia producing a lot of cheap hydroelectric power, with relatively low local demand in the summer, when Southern California power demand is highest. So it makes perfect sense to ship the excess power south in the summer, and perhaps ship SoCal's excess north in the winter.

Other long-distance HVDC lines are used where you have hydroelectric generation located a long way from where the demand is, as for instance near the shore of Hudson Bay.

There are also some very good technical reasons to have large power grids, and to interconnect grids with DC. It has to do with powerflow & stability issues. Everything on an AC grid has to run at essentially the same frequency & phase; individual lines can carry only so much power without overheating; power can't really be stored, but must be used as it produced; and individual power plants & lines can fail for all sorts of reasons, and sometimes need to be taken off-line for maintenance.

[H-Man]

Originally Posted by jamesqf

My former co-workers, electric power systems engineers Heidi, Gail, Carolyn, and Karen, would strongly object to that stereotype :-)

It was said in jest. Your former coworkers should go yell at some of the instructors at the local college, there is at least one that actively tries to get female engineering students to change their major and it pisses me off because gender has nothing to do with ability.

[Xist]

Originally Posted by jamesqf

My former co-workers, electric power systems engineers Heidi, Gail, Carolyn, and Karen, would strongly object to that stereotype :-)

You know, people have never been very accepting of women with facial hair!

Originally Posted by oil pan 4

High voltage DC lines are typically over head.
Capacitance is why all long distance lines are above ground. If they were under ground the wire insulation would absorb so much energy on a 750kv, 60Hz system that only after 25 or 26 miles no power would make it to the other side of the line. The lines capacitance would equal the transmission capacity at that distance.

When I was a kid, we moved into a house that had an electrical tower over the back fence. Dad once said they needed to bury the lines and I thought that it would be prohibitively expensive, but he objected to kids periodically climbing a 125-foot tower.

I guess that it was not just unlikely, but impossible.

[jamesqf]

Originally Posted by Xist

...but he objected to kids periodically climbing a 125-foot tower...

You kids must have been real lucky, since people (who aren't trained linemen, anyway) who climb high voltage transmission towers often don't survive their first attempt :-)

[basjoos]

Originally Posted by jamesqf

Ever stood close to (well, not TOO close, though :-)) to a high voltage power line, and heard the 60-cycle hum? That's power being lost. Changing currents (and AC is always changing, by definition) generate electromagnetic radiation, which is energy lost over & above the resistance of the conductor.



But it is significantly MORE efficient to boost voltage to 1000 kV and send 1000 miles or so as DC, than as A/C.

Another expression of the power being lost is seen if you carry a fluorescent tube with you as you walk under a AC transmission line. The fluorescent tube will light up by itself without any power connected to it.

It also generates electric currents in any wires (fencing, etc.) located next to it. When I ran a single wire electric fence next to a power line that runs through my property, before being connected to the electric fence charger it showed 800v on my voltmeter and would give me a noticeable jolt when I touched the wire (but not even close to the jolt given by the fence charger once it was connected).

[oil pan 4]

I read about some more California insanity the other day.
Looks like last year they banned the sale of obsolete motor oils such as some non-detergent oils used in lawn mowers and air compressors along with SG and SH oils used in motor cycles. Now they are now trying to legislate when you change the oil in your car.