Analysis of Corona on Hybrid DC and AC Overhead Transmission Lines

This article is aimed at calculating the onset voltage of corona on ac and dc conductors of a hybrid transmission line along with corona current-voltage (I-V) characteristic of both the dc conductor operating separately or with ac conductor forming a hybrid line and the ac conductor with and without dc conductor. This makes it possible to calculate the corona power losses on ac and dc conductors. The charge simulation method is applied for evaluating the electric field anywhere around the conductors of the hybrid line and for tracing the field lines emanating from the dc conductor. The onset voltage of corona on the ac and dc conductors is calculated based on the condition of triggering burst-and Triclel-pulses for positive or negative corona. For an applied voltage above the corona onset voltage, the dc corona current is calculated by solving Poisson's equation along with the current density, and its continuity equations through an iterative procedure conducted over the field lines emanating from the dc conductor. The ac contribution to the $I$ - $V$ characteristic of the hybrid line is evaluated by calculating the energy required for space charge oscillation back and forth around the ac conductor per unit time. The presence of the ac conductor decreases the onset voltage of corona on the dc conductor. For any value of the applied dc voltage, the dc corona current increases with the increase of the applied ac voltage. The calculated onset voltage and the corona I-V characteristics on the hybrid line agreed reasonably with those measured experimentally.