Residential ground system currents and magnetic fields

Full text: Measurements of ground currents and magnetic fields have been made in fourteen houses. The measurements indicated that a ground system can be a source of magnetic fields in these houses. In some houses the fields inside sometimes exceeded the fields due to the external power lines alone. In four houses the current in the grounding system was zero, nevertheless these houses were exposed to fields produced by power lines. In some houses a close relationship existed between the measured ground currents at the water meters and the ground system fields inside those houses. The largest value of average ground current was 5.37 A. Contour and surface plots of magnetic fields showed that water pipes influenced the spatial distribution of the magnetic field inside houses. In two houses the external ground current sometimes exceeded the load current of those houses. This is a most unexpected finding. In houses where no ground currents occurred, the value of the magnetic field at the centre of each room was found to be a good approximation to the average of the field throughout that room