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Re: Impedance of Corona or Arcs vs Voltage (fwd)
---------- Forwarded message ----------
Date: Mon, 13 Jul 1998 13:39:23 -0700
From: Jim Lux <James.P.Lux-at-jpl.nasa.gov>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Impedance of Corona or Arcs vs Voltage (fwd)
Tesla List wrote:
>
> ---------- Forwarded message ----------
> Date: Sun, 12 Jul 1998 09:49:04 -0700
> From: lod-at-pacbell-dot-net
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: Re: Impedance of Corona or Arcs vs Voltage (fwd)
>
> >I just thought I would ask. There should be some information on
> > corona loss at least.
> >
> > Terry Fritz
>
> Corona losses increase with the square of the voltage.
> --
>
> -GL
> www.lod-dot-org
that is, the power lost to corona goes as the square of the voltage? In
other words, corona looks like a fixed value resistor? Or, is it that
the corona current goes as the square of the voltage?
I have an equation (due to Peterson) for power lines:
Pcorona = 3.73 K / (D/r)^2 * f * V^2 * 1e-5 [kW/conductor/km)
f is frequency in Hz
V is voltage
D is the phase conductor separation
r is the phase conductor radius
K is an empirical constant which depends on the ratio of the line
voltage to corona onset voltage and ranges from 0 to about 30 with two
distinct "knees" in the curve. The first knee is at about V/Vonset =
1.6, where K = 0.5, and the other is where it sort of flattens out and
asymptotically approaches 30. At V/Vonset = 2, K=10.
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 surface condition also affects the corona starting voltage. There is
a table of these factors at
http://home.earthlink-dot-net/~jimlux/hv/corona.htm