Exposure to magnetic field harmonics in the vicinity of indoor distribution substations

Due to possible health effects of electric and magnetic fields, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) published in 1998 guidelines in which upper limits for public and occupational exposure were established. The guidelines are widely referenced by the EU directive of 2004. Thus, in Europe we have passed the time for discussion about the possible biological effects of magnetic fields and the duration of exposure to be allowed. Furthermore, in 2003, ICNIRP expanded their guidelines by taking into account the harmonic components of the magnetic field with phase angles. This statement has not been referenced widely. The aim of this study was to investigate magnetic fields, especially the harmonic components, in electric distribution (20/0.4 kV) substations from the public and occupational exposure point of view. The main finding is that the harmonic content of the magnetic field can dominate the exposure. The harmonic contents analyzed following the original ICNIRP guidelines varied between 49 and 74%. When taking into account the magnetic field phase angles, the harmonic content was only between 16 and 62%. By taking into account only the amplitudes of the harmonic components, ignoring their phase angles, the content of harmonic components is overestimated, on the average, by 30%.