Experimental investigation of negative DC corona on conductor bundles: A comparison with positive corona

Negative DC corona on conductor bundles is experimentally investigated in the coaxial configuration. The dependence of the corona characteristics, namely inception voltage and current, thus also inception field and power losses, on bundle radius and number of conductors in the bundle is assessed. The corona inception voltage of conductor bundles is highest at a bundle radius that corresponds to the minimum electric field strength at the conductor surface. The corona inception field strength of conductor bundles can be considered, with reasonable accuracy, as equal to that of the single conductor. Polarity effects on DC corona characteristics are assessed through comparisons with positive DC corona. For both polarities of applied voltage, the corona current can be accurately estimated through a modified Townsend quadratic formula using appropriate values for ion mobility.