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Keywords:

  • body resistance;
  • dosimetry;
  • heart current;
  • low frequency;
  • realistic human model;
  • SPFD;
  • touch current

Abstract

Characteristics of power-frequency touch current inside an anatomically realistic human model of Japanese adult were numerically analyzed under various scenarios of current paths using a modified scalar potential finite difference (SPFD) method. Then, complex distributions of the current density in the model were visually illustrated. Results of the dosimetry of current density for excitable tissues indicates that the touch current within the reference level (0.5 mA) does not always satisfy the basic restriction of current density in the light of ICNIRP guideline for general public. Two sets of the internal body resistances Ri (i.e., 1130–1510Ω and 1460–1920Ω) are obtained, depending on the conductivity sets used. Although Ri considerably depends on the current scenario concerned, the highest values of Ri were obtained for the hand-to-hand scenario, regardless of the conductivity set. The inhomogeneous model always gives a higher value of Ri than does the homogeneous model that has a single conductivity equivalent to the weighted-average conductivity of the inhomogeneous model. It is found that the conductivity of muscle has significant influence on Ri, and that the resistance around the wrist and ankle is one of the predominant parameters to decide Ri. It is clearly shown that the current scenarios affect the pattern of the heart current flow, especially the direction of it, to a large extent. It is found that a current of 34–40% of touch current flows into the heart, and then the heart-current ratio is remarkably larger than old data. The heart-current factors of around 0.85 obtained are almost independent of the current scenarios, unlike those indicated in IEC60479-1, provided that the direction of heart current is ignored. © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.