Re: Impedance of Corona or Arcs vs Voltage (fwd)

---------- Forwarded message ----------
Date: Wed, 15 Jul 1998 21:33:27 -0700
From: "Antonio Carlos M. de Queiroz" <acmq-at-compuland-dot-com.br>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Impedance of Corona or Arcs vs Voltage (fwd)

Jim Lux wrote:

> The corona onset voltage (for AC) is roughly where the E field strength
> gets over 30 kV/cm.  This is mostly determined by the radius of
> curvature. If the radius of your "thing" is 1 cm, then when it reaches
> 30 kV, corona will start. The presence of nearby conductors will
> definitely affect the E field distribution, and hence, the corona onset
> voltage.

The rule about the 1 cm of radius for each 30 kV is correct for a polished sphere,
or a surface curved in all directions, for peak voltage values, including DC.

Do you know what is the rule for a long cylindric conductor, as a high-voltage
cable? It is not this, as 500 kV power line cables don't appear to have 47 cm 
of diameter (500*1.4142/30*2).

(too lazy to make the derivation)

Antonio Carlos M. de Queiroz