Study Upon the Influence of Bundle Configurations on Corona Losses

In the first part of our paper is presented in some details the issue of corona discharges produced in the immediate vicinity of the overhead high voltage power lines. The deterministic connection between the potential gradient at the surface of the active conductors and the initiation of corona discharges is theoretically approached. The decrease of electric field strength in the very surrounding area of the active conductors reduces the risk of corona discharges, but at the cost of increasing the electric field strength at the standard height (from the perspective of human exposure) of 1 m from the ground. We have considered a perfectly balanced 400 kV double-circuit three-phase overhead line, using suspension towers SN 400231, transmitting 1580 A (rms value) per phase in 4 distinct variants: a single conductor, respectively bundles of 2, 3 or 4 (parallel) subconductors. For each bundle, we have considered two representative types of spacer-dampers:side of 3 and 5 dm, respectively. For each case and sub-case, simulations have been performed using ANSYS and EMFACDC software, drawing the lateral profile of the electric field strength at three representative heights: 1 m from the ground, the height of the conductors (9 m) and the symmetrical height (above the conductors, 17 m from the soil). Useful conclusions have been drawn, both to reduce the risk of initiating corona discharges and to protect residential areas from electric field strength generated by the bundle-type configurations of over 220 kV overhead power lines.