Re: Corona breakout voltages?

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

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Jim,

At 09:16 PM 10/12/2002 -0700, you wrote:
>
>----- Original Message -----
>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: <tesla-at-pupman-dot-com>
>Sent: Saturday, October 12, 2002 7:41 PM
>Subject: Corona breakout voltages?
>
>
>> Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
>>
>> Hi All,
>>
>> There is this well known formula for corona of 3MV per meter of radius.
>If
>> I have a 1 meter radius sphere, I can but 3,000,000 volts on it before
>> corona breaks out.
>>
>> So I used to work on 375kV power lines, they were about 1 inch in diameter
>> (0.0127m radius).  0.0127m radius suggest a corona voltage of 38,100
>volts.
>>  So at 10X that, those lines should have been glowing and streamering like
>> crazy!!!  375kV was also an "RMS" voltage...
>
>But, were those "bundled" lines, which increases the effective radius?

Yes,  Steel rope core with thick aluminum wires spiraled on the outside.

>Also, corona inception voltage isn't exactly matched to free air breakdown
>field... you can get a low grade corona which creates a semiconducting
>ionized sheath increasing the effective diameter of the conductor..not that
>I'd want to get anything grounded near it, for the flashover potential is
>high, but, out in free space, you might get some crackle and hiss, but not a
>whole lot of visible corona (in UV on the other hand...).   You'll see
>corona rings at the insulator strings, too..

Yes!!!!  that's what I was thinking...  The area around the conductor just
charges up an no more corona...  I little thougher at 38kHz I would think
but maybe not...

>
>>
>> I am having trouble getting little spheres to corona at the voltage I
>think
>> they should (seems to take far far higher voltage) and I think what ever
>> held corona back on those high voltage power lines is also holding back
>> corona in my sphere experiments.  Is the surrounding air just charged up
>> and acts to reduce the e-field or something???
>>
>> I am just wondeing if anyone has any insight into this or can tell me what
>> I am missing in all this?
>
>HV is strange...

This I have noticed :o)))))

>
>Mostly, there's a big difference between uniform and nonuniform fields, in
>terms of observed effects.  Running small diameter conductors at high
>voltages, you've got a nonuniform field.

If you have any further info or references on such effects, we ARE
interested ;-)))  We are studying this on the TSSP list and we seem to have
opened a barrel of monkeys here ;-))

Cheers,

	Terry