Limits of lightning protection systems

Positive first strokes, less frequent but more powerful than negative return strokes, require a larger conductor. If the skin effect is accounted for, a near maximum value of the action integral of positive lightning can be estimated from the sizes of conductors specified by established building codes. The conductor size for watercraft could be increased: (1) to match that used for structures on land; (2) to avoid exceeding the maximum operating temperature of a dielectric hull; and (3) to limit magnetic stresses caused by 90° bends in conductor paths predicted by Ampere's law. Connecting a conductor at right angles to a ground plate may be problematic; a linear grounding electrode alternative is discussed. Destructive magnetic force can be caused by surface current on: a solid conductor; a hollow conducting mast; or a horizontal ground plate. Electric shielding, unless struck directly, might protect a dielectric hull, except from a subsequent stroke with a short current risetime. Thus, lightning protection systems do not always work, and lightning is best avoided.