The effect of stranded conductor geometry on DC corona in the coaxial cylindrical electrode arrangement in air

The effect of stranded conductor geometry on the salient characteristics of DC corona, namely corona inception voltage, corona conductance and the associated power losses is experimentally investigated in the coaxial cylindrical electrode arrangement in air. The number of strands of the conductor has a greater impact on the characteristics of positive than negative corona. Under conditions of high absolute humidity, corona conductance, thus also losses depending on conductor geometry can be higher for positive than negative corona. Breakdown, only slightly affected by stranded conductor geometry, is greatly facilitated by the space charge associated with multiple coronas occurring along the energised conductor. An empirical expression for the estimation of the irregularity factor of overhead transmission line conductors is proposed, accounting well for the effects of stranded conductor radius, stranding ratio and relative air density.