In high-voltage techniques, electrical discharges represent complex problem. The results of the research on the breakdown phenomena in high voltage electrical apparatus insulated by gas can be employed to obtain external and internal insulation design. The electrical discharges can be employed in various applications. The mechanisms of the electrical discharge and the breakdown voltage characteristics of air gaps in the presence of third electrode were investigated in this paper. Breakdown voltage variations are discussed with the parameters influencing the discharge mechanism such as the gap geometry and the applied voltage at the electrode discharge. The results with different geometries of electrodes show that the electrical breakdown mechanism depends on the electrode shape and applied voltage.