A simple model for calculating residential 60‐Hz magnetic fields

Abstract

A model is presented that permits the calculation of densities of 60-Hz magnetic fields throughout a residence from only a few measurements. We assume that residential magnetic fields are produced by sources external to the house and by the residential grounding circuit. The field from external sources is measured with a single probe. The field produced by the grounding circuit is calculated from the current flowing in the circuit and its geometry. The two fields are combined to give a prediction of the total field at any point in the house. A data-acquisition system was built to record the magnitude and phase of the grounding current and the field from external sources. The model's predictions were compared with measurements of the total magnetic field at a single location in 23 houses; a correlation coefficient of .87 was obtained, indicating that the model has good predictive capability. A more detailed study that was carried out in one house permitted comparisons of measurements with the model's predictions at locations throughout the house. Again, quite reasonable agreement was found. We also investigated the temporal variability of field readings in this house. Daily magnetic field averages were found to be considerably more stable than hourly averages. Finally, we demonstrate the use of the model in creating a profile of the magnetic fields in a home.

Comparison of residential power-frequency magnetic fields away from appliances in different countries

“…The other study [Mader et al, 1990] found 24-h GM ϭ 48 nT, compatible with the results from the United States, particularly considering that this was a measurement of vertical field only.…”

“…In principle, the result of a field measurement will depend on whether the meter used is sensitive to harmonics or not. Most surveys used instruments with a frequency response that would include the relevant harmonics, but some studies [Eriksson et al, 1987;Kaune and Zaffanella 1994;Mader et al, 1990;Merchant et al, 1994a,b;Hansson Mild et al, 1996;Zaffanella, 1993] measured the fundamental (50 Hz or 60 Hz) only. In practice, even a 25% harmonic content would increase the rms field by only 3%, a negligible amount in the context of this paper.…”

Biologic effects of prolonged exposure to ELF electromagnetic fields in rats: II. 50 Hz magnetic fields

“…Field exposure covered about 70% of the animals' lives before sacrifice. The applied magnetic flux density was about one order of magnitude greater than the maximum affecting humans in residential areas in the vicinity of overhead transmission lines and around household appliances [Mader et al, 1990;Kavet et a]., 1992;Mader and Peralta, 1992;Conti et al, 19931. The choice of a magnetic flux of 5 pT met the basic methodological requirements of exposing living organisms to realistic, low-intensity magnetic flux densities likely to induce alterations, if any, that are not directly related to the very small induced current densities.…”

Characterization of power frequency magnetic fields in different environments

“…It is possible sometimes to develop semi-analytical methods if some kind of statistical correlation exists between the magnetic field and the principal currents of the dwelling, 1~1 , ILZ, I N , and Ig. A semi-analytical method has recently been proposed [3], but it requires actual measurements of currents and magnetic fields in the dwelling.…”