Abstract: During the production of, for example ozone, an electric corona discharge is generated in atmospheric air by means of the high-voltage generator, so that ozone is formed from atmospheric oxygen. The high-voltage generator applies a high voltage between two electrodes (4, 14) in a discharge chamber; the electrodes are insulated from one another by a high-voltage insulator (6) which also acts as a dielectric. Electric breakdowns can occur through the insulator (6), so that in the course of time the surface of the insulator is damaged. The insulator then loses its insulating effect. In order to counteract this phenomenon, the exceeding of a predetermined current threshold value by the discharge current is detected in the high-voltage generator; a microprocessor (46) determines the number of times that said threshold value is exceeded per predetermined time interval, and the high voltage is controlled to a lower value if the number of times per predetermined time interval is too high.