Low Voltage Distribution Transformers: Analysis of the Exposure to ELF Magnetic Fields

Modern residential, industrial or commercial buildings may be grounded through a system defined as "TN- Island grounding system". This is an effective way to protect both persons from shock hazard in installations and to greatly limit electrical interferences among power systems. This earthing system, which is aimed to promote electrical safety, better functionality, and lower costs, utilizes single-phase separation transformers installed in the unit grounded at the mid-point of their secondary side. By introducing a new source of power frequency (i.e. extremely low frequency) magnetic fields into the premises, the presence of such additional pieces of equipment in the environment, might expose persons to their potential adverse health effects, as well as, sensitive electronic equipment disturbances. This paper seeks to clarify this matter by evaluating the ELF magnetic fields, as produced by the user\´s own equipment and by other units eventually present in the vicinity.