Optimization of Corona Effects in Small Air Gaps Stressed by DC Voltages

In the present paper methods of minimizing or maximizing the values of the Corona onset voltage and the Corona current in small rod-plate air gaps are investigated. The geometry and the way of grounding and charging the electrodes, (Ground Effect), the gap length, the existence of barrier in the gap (Barrier Effect), and the conditions of the air in the gap, are some factors, which influence greatly the distribution of the electric field in the gap, and hence the above values. Combining experimental and simulation-theoretical work, it is resulted that: a) the electrode chosen to be ground, strongly influences the distribution of the field and hence the Corona onset voltage and the corona current in rod-plate air gaps. When the rod is grounded the value of the corona onset voltage is higher and the corona current is significantly smaller. b) A dielectric barrier, when placed in specific positions in the gap, increases the Corona onset voltage to a maximum value, and annihilates the Corona Current.