Finite difference calculations of current densities in a homogeneous model of a man exposed to extremely low frequency electric fields

Abstract

This paper presents three-dimensional finite difference calculations of induced current densities in a grounded, homogeneous, realistically human-shaped phantom. Comparison is made with published experimental values of current density at 60 Hz, measured in conducting saline manikins with their arms down by the side. The congruence between calculation and experiment gives confidence in the applicability of the numerical method and phantom shape to other configurations. The effect of raising both arms above the head is to reduce the current densities in the head and neck by ∼50% and to increase those from the thorax downwards by 20–30%. A sensitivity analysis was performed on the shape and dimensions of the phantom, from a 45-kg, 1.5-m-tall person to a 140-kg, 1.9-m-tall person. When the phantom is grounded through both feet the current densities range from 50 to 90 μAm⁻² in the head (all values for a 60-Hz, 1-kVm⁻¹, vertical applied field), 70 to 140 μAm⁻² in the thorax, 150 to 440 μAm⁻² at the crotch, and 500 to 2,230 μAm⁻² in the ankle. When grounded through only one foot the current densities at the crotch range from 400 to 1,000 μAm⁻² and from 1,000 to 4,400 μAm⁻² in the ankle of the grounded leg. Scale transformations of the short-circuit current with phantom height, weight, and surface area are confirmed.