Corona current in a cactus-like electrode under natural-like electric field: Comparison with a single-needle electrode

In this paper a working hypothesis was proposed: If an air stream can remove the corona space charge close to a corona source, then the corona current is modified in a different manner in different types of corona electrodes. This phenomenon must be polarity dependent. To test this hypothesis two types of corona electrodes were tested: a cactus-like and a single-needle electrode under a natural-like electric field of both polarities. Both corona current sources were tested inside of a shielded room to avoid high frequency interference produced by external HF sources and were immersed in a constant DC electric field of both polarities, while the corona current and the background electric field were measured. In a plate-to-plate electrode arrangement a DC voltage was applied to the tested electrodes during 3 subsequent 30 s time intervals. In the second time interval a 7,06 m/s air stream was applied to the measured electrode, while in the first and third ones the air was calm. Results show that the measured corona current is larger in the presence of a current stream and in some specific cases of air flow velocity and background electric field, the measured current is larger in the single-needle electrode. Those results are polarity dependent.