A study of corona phenomenon on hybrid AC/DC transmission lines

The factors affecting corona phenomenon on hybrid AC/DC transmission lines are investigated using a single-phase AC (50 Hz) /single-pole DC reduced-scale model. The variation of DC corona current with DC voltage follows the same conventional formula for rod-to-plane gaps, where the exponent of conductor height increases with DC voltage, but is slightly affected by interspacing. While the AC corona current is inversely proportional to the conductor height with a power range from 0.7 to 0.8, it also increases with the decrease in interspacing. A field computation program is used to model both an AC 132-kV double-circuit transmission line and analog hybrid lines. The results reveal that hybrid lines cause higher radio noise but the audible noise is nearly the same as or lower than that for the AC double-circuit lines. The trend of the experimental results is in agreement with the computed number of streamers and electric field profiles.