Re: Why no corona? AC / DC transmission lines

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
> 
> Original poster: "Mccauley, Daniel H by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <daniel.h.mccauley-at-lmco-dot-com>
> 
> Sure, there are transmission lines that run up to 768kV or better.
> I've even heard of megavolt lines (anyone know where these are?)
> 
> >>>>>>They have quite a few now 1 Megavolt DC transmission lines which are
> basically bipole
> transmission lines (+/- 500,000VDC). 

	That is the present "Pacific Intertie" which has, I believe, been
upgraded to +/- 600 kV.  I don't know design details of the conductors,
but from the ground they just look like large cables.

> Seems Edison could be happy right now.
> DC high voltage lines are run
> because of their lower reactive losses and are under a lot of study right
> now.

	There are also matters of line stability which are mitigated by the use
of HVDC.

> I think i heard before that over 30% of power is lost in AC high voltage
> power lines just due to losses. 

	That is a question of economics.  Reducing the line loss (larger
conductors, higher voltages) cost $, as does the lost power.  There is
thus an optimum loss which will depend on the particular installation. 
I believe a loss of 10% would be more typical, but have no data.

> Of course in DC transmission lines you do
> get a large amount of losses in the step-up / step-down converter systems.

	Modern solid-state converters are probably a lot more efficient than
conventional transformers, either of which can give better than 98%
efficiency.

Ed