Numerical evaluation of 60 Hz magnetic induction in the human body in complex occupational environments

Exposure to 60 Hz non-uniform magnetic fields is evaluated using realistic configurations of three-phase current-carrying conductors. Two specific sce narios are considered, one involving a seated worker performing cable maint enance in an underground vault with conductors carrying 500 A root-mean-squ are (rms) per phase, and the other involving a standing worker during inspe ction of a 700 MW generator with conductors carrying 20000 A (rms) per phas e. Modelling is performed with a high-resolution (3.6 mm) voxel model of th e human body using the scalar potential finite difference (SPFD) method. Ve ry good correspondence is observed between various exposure-field measures, such as the maximum, average, rms and standard deviation values, and the a ssociated induced field measures within the whole body and various organs. The exposure fields produced by the lower currents in the vault conductors result in correspondingly low current densities induced in human tissues. A verage values are typically below 0.2 mA m(-2). On the other hand, the aver age exposure related to the inspection of the generator isophase buses is a bout 1.5 mT at a distance of 1.2 m from the conductors. This field induces organ average current densities in the range of 2-8 mA m(-2), and peak (max imum in voxel) values above 10 mA m(-2). A comparison with uniform field ex posures indicates that induced fields in organs can be reasonably well esti mated from the accurately computed exposure fields averaged over the organs and the organ dosimetric data for uniform magnetic fields. Furthermore, th e non-uniform field exposures generally result in lower induced fields than those for the uniform fields of the same intensity.