The Magnitude of Corona Point Discharge Current

Abstract

The magnitude of corona point discharge current is calculated by an approximate quantitative theory. Using plausible values for one adjustable constant, the current i agrees exactly with experiment. For an isolated point of potential Vp in a wind of speed w, i=1.315∈0w(Vp−V0p) [Eq. (I)], or for a paint of height h in an ambient field E0, i=3.9∈0kE0(Vp−V0p) [Eq. (II)], where Vp=E0h, the ion speed v is w or kE0 depending upon circumstances, k is the ion mobility, and V0p a starting voltage (SI units). The model involves a space charge sphere of radius r3=1.44k Vp/4v plus a downstream space charge cylinder, and explains the variation of current, or lack of it, with point potential, ambient field, polarity, ion mobility, wind speed, geometrical factors and altitude as it affects mobility and the plasma about the point. One consequence of the variation of r3 is that many points on a tower in a weak field and strong wind can yield many times the current of one point, whereas the same array in a strong field under a thundercloud or in light wind may yield no more, possibly less, current than one.