HV DC transmission coversion to AC

Ah, Wikipedia to the rescue again:

--Damon

Besides the Wikipedia article Damon posted a link to, you might try searching for articles at the Bonneville Power Administration website. I remember finding some very interesting stuff there about the Pacific Intertie, between Sylmar, CA, just N. of Los Angeles, and the Bonneville dam on the Columbia river. At the time, probably ten years ago, I recall they were still using thyratron-type tubes ("mercury arc rectifiers??"), and an article I found was talking about the very high cost of retrofitting the inverter station to solid state. I believe the Sylmar station was pretty seriously damaged by a large earthquake in 1972. More stuff on the Pacific Intertie here:

Cheers, Tom

See Pacific Intertie:

The system has been upgraded over the years. It started with mercury arc switches (thyratrons) for inversion and has been upgraded several times. The most recent upgrade uses light activated thyristors (SCR's) from Siemens in the inverter.

The line carries plus and minus 500kVolts at up to 3100 megaWatts.

guess this is the kind of stuff you want to work the first time, probably not much left to try again if something goes even a little wrong :)

-Lasse

Ignitrons, the dumbest tubes ever designed.

John

I sense a good rant itching to come out...okay, John, what's wrong with Ignitrons, exactly?

Cheers,

Phil Hobbs

They're pretty hard to beat at high voltages. I've used them at 36KV at 100's of Amperes.

...Jim Thompson

It's no good explaining puns. No good at all.

John

Ah. Here I was hoping that it was something like the 5 milligrams of mercury.

Cheers

Phil Hobbs

An ignitron has a pool of mercury to serve as its cathode. The Wikipedia article on them appears to agree with how I remember them being described in old books.

- Don Klipstein ( snipped-for-privacy@misty.com)

I thought there was a big pool of the stuff. The power ignitrons are huge, like a beer barrel.

John

There probably is. I was referring to last week's argument about pollution from CFLs.

Cheers,

Phil Hobbs

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

Hell, they're routinely used at as much voltage and a thousand times more amperes. Think quarter shrinker. :-) Great rise time, cheap to build (air is a quite suitable arc medium), great capacity.

Tim

The Science Museum in London used to have a working one on display. IIRC the power for the museum flowed through it. Lots of blue flashes etc.

A mere 6 amps - what could possibly go wrong!

Dirk Bruere at NeoPax wrote in news: snipped-for-privacy@mid.individual.net:

A mere 3 gigawatts? Not for very long! >>POOF

;)

-Lasse

Wasn't that a glass-bulb three (or six)- phase mercury arc rectifier, like

Chris

The

in

Yeah, I remember about 35 years ago coming across the transmission line a bit north of its Sylmar terminus when my brother and I were out for a drive in the hills and seeing if a compass was affected by the field under the lines. Not that we could detect, but we also had no way of knowing what current was being carried at that moment anyway. It might be interesting to calculate how much the catenaries between towers move because of interaction of their magnetic fields when the line is carrying full power. Assuming the lines are reasonably high conductivity (copper or aluminum), the resistance must be on the order of 25 milliohms/mile-conductor, or 50 milliohms per round-trip mile. The whole line then is probably a little under 50 ohms, assuming it's not a really hot day. At 6000 amps, that's a lot of power and a voltage drop of close to 30kV. Wow. I wonder how efficient the AC--

Cheers, Tom