🚀 go-pugleaf

In article <1jmre4INNfks@rave.larc.nasa.gov> kludge@grissom.larc.nasa.gov (Scott Dorsey) writes:
>In article <1993Jan21.095254.62979@cc.usu.edu> slmdj@cc.usu.edu writes:
>>He is an assistant city engineer for Adelanto, CA, and told me that the way
>>their power is distributed to a large substation is Direct Current!  He said
>>that the DC is then 'phased' or 'converted' so that there is a three-phase AC 
>>line to the city distribution grid.  Neither of us have any idea how this could
>>be accomplished at such power levels (an entire valley, I think!)
>
>They do it with silicon, believe it or not!  They have thyristor switches
>taller than a man, and switch the DC.  This way, they can run DC on the
>long lines at high voltage, which is advantageous since they get more
>power over the same wire (since the limiting factor on the lines is the
>peak voltage before arc-over, and the peak voltage on DC is also equal
>to the average).

The transmission system I am familiar with had two lines
which carried current in opposite directions.  If one line was
down due to a fault or maintainance, they would/could use earth
return!

Because modern DC transmission first became common in Europe,
the term "valve" is often used to describe the switching devices.
One device looks like a hockey puck, and these are stacked together
to form a switch.  The whole thing resides in a "valve hall"
which is completely enclosed by copper for RFI/EMI reasons.

Another advantage of DC transmission, I think, is that it solves
some network stability and synchronization problems.
For example, you can tie together two unsynchronized networks,
or two network where want to minimize the interaction.
I don't know if it would apply in the case you mention though.
The cost of the converter stations, used to at least, make
DC transmission only economical for limited applications.

Gene

>--scott