Physical and computer modeling of military earth grounding practices in a HEMP (High-Altitude Electromagnetic Pulse) environment

Military grounding practices compatible with hardening electronic systems to high-altitude electromagnetic pulse (HEMP) illumination are considered. This study concerns the grounding practices outlined in MIL-STD-188-124, Common Long-Haul/Tactical Communications Systems. Three standard grounding schemes and one new scheme were chosen for study at a 10:1 scale, illuminated by a 59-V/m peak simulated HEMP. There were several significant results: (a) The theoretical technique in general agrees to within a factor of three with the experimental results, (b) The type end of earth ground system does not appear to be important, and (c) Intrasite transients tend to be dominated by electromagnetic coupling to completed conductive loops. When the loop is broken, the transient is characterized by the half-wavelength resonance of the conductor. Grounding paths which do not form part of the loop do not contribute significantly to the transient in the loop.