Abstract <p>The paper presents the results of calculations and experiments to determine the primary amplitude and time characteristics of electrical breakdown in long air gaps in a point-to-plane double-electrode discharge system (DEDS) by a standard switching aperiodic high-voltage pulse of the time configuration, <i>T</i>_<i>m</i>/<i>Т</i>_<i>p</i>&#xa0;<i>≈</i> 200 μs/1990 μs<i>,</i> of positive polarity. Approximate calculation relations are obtained to find the breakdown time, <i>T</i>_d, breakdown (discharge) voltage, <i>U</i>_d, and breakdown strength, <i>E</i>_d of a strong electric field for this DEDS, averaged over a minimum length of <i>l</i>_min ≥ 1 m of these gaps. The proposed engineering approach to determining the values of <i>T</i>_d, <i>U</i>_d, and <i>E</i>_d is based on the results of an approximate calculation in a long air gap of a point-to-plane DEDS of a sharply inhomogeneous strong electromagnetic field that produces a spherical zone with a radius <i>r</i>_<i>i</i> of active impact ionization of its atmospheric air by electrons. This occurs near the lower sharp edge of the upper potential electrode point of the DEDS, wherefrom a positive discharge leader develops towards the lower grounded electrode plane of the DEDS.</p>