Experimental investigation of positive DC corona on conductor bundles

The salient characteristics of DC corona discharge on conductor bundles, namely corona inception voltage, corona current and the associated power losses, are experimentally investigated in the coaxial cylindrical electrode arrangement in air. The corona inception voltage increases markedly with increasing number of bundle conductors. There is an “optimum” bundle radius, increasing with number of bundle conductors, for which corona inception voltage attains its highest value. Except for relatively small bundle radii, the corona inception field of a conductor bundle is approximately equal to that of a single conductor. For a fixed applied voltage and a given bundle radius the corona current decreases as the number of bundle conductors increases. An empirical expression is proposed for the estimation of the corona current, therefore also power losses, as influenced by the applied voltage and the geometry of the conductor bundles.