Re: transmission lines from transformer /was: First Light HELP

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>

Hi David,

On 18 May 2005, at 16:54, Tesla list wrote:

> Original poster: DRIEBEN@xxxxxxxxxxxxxxx
>
> Ed, Drew,
>
>
>  > Original poster: Esondrmn@xxxxxxx
>  >
>  > Drew,
>  >
>  > Not sure about the HV cables hissing.  Do you have them laying on >
>  the > cement?  What kind of wire are you using?  How close together
>  are > they?  I > use RG213 with the outer jacket and ground sheath
>  removed and the > cables > are sitting on 2 x 4s on the cement.
>
> Not sure that this is recomended but I use x-ray HV cables
> with the grounding sheaths intact and gronded at the mains
> ground at the pole transformer. They certainly don't hiss
> in this setup although this may be a NO-NO from an RF kick
> back stand-point?? I've heard that this type of setup also
> causes a "Blumline effect" which causes voltage levels to
> reach much higher than the output voltage of the transformer
> itself, but I have not had any pole pig transformers to even
> hiccup from running like this. One reason I do it this way
> is to stop the hissing and to make it safer if the lines are
> touched while energized. I know the electrical utility com-
> panies must use this method on all of their underground power
> lines. Any observation/comments from others on this matter
> are welcome....

The problem is that the shielded cables behave like a transmission
line and together with serious mismatches at both ends and shock
excitation by step functions from the gap, can easily be excited into
ringing at one or more of its resonances. In general, any long lines
are prone to exhibit this problem and I've seen it occur with
unshielded long lines as well. In fact it killed one of NSTs and
damaged another type of transformer which needed partial rewinding of
its secondary.

Malcolm