ECN Forum Forums General Topics of the Trade General Discussion Area Local HV distribution

Thinking about it, I must have seen multi-voltage poles on my travels in America, but it just didn't register in my mind.

The only significant sharing of poles here is that telephone cables are often placed lower down on 240/415 4-wire poles, but they're never run on anything higher.

By the way, our standard HV delta voltages are 11, 33, 66, 132, 275, and 400kV. The last three are always on the big metal lattice towers.

Standard transmission voltage in Southern California is 66,115,220,345, and 500KV. There is also a direct current line that runs near my house that operates at about 750KV. Other parts of the country have AC lines that operate at up to 750KV. None around here though.

I think there was talk of a higher voltage transmission some years ago, but nothing ever came of it. We're probably too small a country to make the expense of going to anything over 400kV worthwhile.

(The whole of the U.K. - England, Scotland, Wales, & Northern Ireland combined - is about the same area as Wyoming.)

I'm not aware of any DC transmission within the country, but we do have an underwater DC cable linking us with France, which at the closest point is only 22 miles across the English Channel.

France is an hour ahead of us, plus they end to work and eat at different times, so it's o our mutual benefit. Been there for decades.

A while back I said that we don't normally have different voltages on the aame poles for HV lines. Well, that's always been the case here as far as I'd ever seen, but just to prove me wrong I saw it today barely 15 miles from home!

I had to ride the train back from Norwich and saw some HV transmission lines that aren't normally visible from any road. I wasn't close enough to make out the signs, but from the insulators (fairly standard across the country) it looked like a standard 3-ph. 11kV and a 3-ph. 33kV line converging from slightly different directions.

They ran on opposite sides of three cross arms for about a half mile before diverging in different directions again.

Very unusual!

Well I am bringing this back up because I have a few examples. The DC line I mentioned is 500KVDC not 750KV as I thought. It Is owned by The LADWP and originates in Utah. Here is a picture of one of the towers.

Note the three conductors per leg.

Here is an example of mult circuits on one pole.

This is 12.47KV on the bottom, 34.5KV in the middle and either 66KV or 115KV on top. Hard to tell as the insulators are similar on these systems.

Nick,

I have seen the High Voltage DC lines at SCE's Sylmar location [off the I-5 at the junction for highway 14 to Antelope Valley / Lancaster]. They come in with a gang load of 138 KV and 220 KV AC circuits sprouting from every direction.

Was going by there yesterday on the way back from Saugus, and got a somewhat better look at them.
That's one heck of a trek - Saugus to Anaheim!
And, of course, I had to pick 5:00 PM to head into LA!!! Double

There's only 2 conductors per leg on these poles, where the ones going through the Desert [as you've shown in the images] have 3 per leg.

Anyhow, thanks for the info on the HVDC circuits!!! I had no clue to their Voltage or place of origin!

Scott SET

Scott, I found a great link for learning about DC transmision. Go to http://www.abb.com/
They have an informative section on DC transmision. What, who, why how and where.

Just to clarify, since it is hard to see in the picture, the conductors on top are static lines. You can't see it but there are three per leg on the lower + and - lines.

On the second pic, is that a multi-pair telephone cable below the HV lines?

Paul,
It is either telephone or cable TV. I can't tell from the picture and was not paying attention when I took it. Next time I am out that way I'll check and post back.