Re: Why no corona?

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Monday, September 09, 2002 7:53 PM
Subject: Re: Why no corona?


> Original poster: "Christopher Boden by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <chrisboden-at-hotmail-dot-com>
>
> They actually do have problems with corona I would guess. I know for a
fact
> that I've heard the familier hiss on more than one occasion while standing
> under a HV line.

A lot of that crackle and hiss is surface leakage over the dirty insulator
surfaces.  High humidity makes the conductivity higher, aggravating the
problem. Late at night or early in the morning it is a)humid and b)quiet, so
it's more noticeable.

Also remember that the really high voltage lines are rather
> rare. Sure, there are transmission lines that run up to 768kV or better.
> I've even heard of megavolt lines (anyone know where these are?) that run
> across deserts.

The big DC link (+/- 500 kV, as I recall) that runs on the west coast runs
down the Owens Valley along US395 to the Sylmar converter station in the San
Fernando Valley (Los Angeles Area).

The infamous Path 15, in the California Central Valley, will be upgraded
with a third 500 kV link to add capacity of 1500 MW. (1500 MW -at- 500 kV =
1000 A per phase (3000A total)...we in the tesla coil business with a few
tens of kW are pikers by comparison)
(path 15 is now 2 500 kV links and 4 230kV links... drive down I5 and you'll
see it between Los Banos and Coalinga (where the stockyards are))

I note that the real limit on these lines is the temperature of the wire
(typically limited to 100C)...

There's also a 500 kV line near Gorman (path 26) which is notable because
they had a brush fire burning under it in June which caused a trip

In California, you can get all sorts of fascinating (to a HV enthusiast)
information at: http://www1.caiso-dot-com/thegrid/operations/register/index.cgi

You can search for all 500 kV transmission lines, for instance...

 But the vast majority of power lines are small, under
> 14.4kV. Also, while we run at 400kV regularly, their 400kV would act a lot
> differently. Even though the voltage is the same, the frequency is a lot
> different.


 And weather it's a megavolt line across a desert, or the 120 in
> your wall outlet, it's ALL at 60hz. Things get freaky with frequency.
>
> I've heard corona on humid or rainy days, and in the winter (when it's
> really dry) as well. I've seen the long, graceful bends in HV Buss at
> substations (corona likes sharp points). So my guess would be that they DO
> have problems with corona, you just don't notice it much because it's very
> quiet compared to the usuall surroundings, and it's not bright enough to
> attract attention, in fact, in broad daylight it's difficult to see a 6'
arc
> from a TC, a little purple glow, never.