Influence of a Bias Voltage on the Characteristics of Surface Discharges in Dry Air

Surface discharges (SDs) in a three‐electrode system have been investigated. The electrode system consisted of an upper plane electrode (to apply a bias voltage) and a SD arrangement with metallic strip electrodes on the upper side of a dielectric plate, while the reverse side was covered with a metallic layer. When high voltage was applied to the metallic layer with grounded strip electrodes, SDs appeared in between the strips on the dielectric. The characteristics of SDs have been already the subject of a number of investigations with respect to different plasma technologies. In the present work, the influence of a dc bias voltage on the SD characteristics has been investigated, especially on current, active power, discharge structure and ozone formation in a flow of dry air. When applying dc voltages up to 20 kV of both polarities, a rising direct current appeared with densities up to more than 50 μA · cm−2. This effect was more pronounced with negative polarity. An influence of the air flow rate on the direct current was also registered. The structure of the SD observed with a CCD camera became more diffuse with a dc bias voltage. Furthermore, it depended on the kind of dielectric material under investigation. With negative dc voltages of more than 7 to 9 kV, filamentary discharge structures appeared in the gap between the plates. The structure of these discharges and the conditions of their appearance also depended on the dielectric material. Image of discharges on a rough pyroceramic surface (the dark strips mark the position of the electrode).