Study of Low Frequency Magnetic Field of Indoor Distribution Substations

In this paper we presented some measurements of the low frequency magnetic field from indoor distribution substation. Using two automatic measuring instruments we made both spot measurement and automatic long-term survey presenting the spatial and temporal variability of the magnetic field in five areas with indoor distribution substation. Correlating the time of spot measurement, with that of automatic survey we estimate the magnetic field values to reduce the errors due to the temporal variation. With the values obtained after estimating the field, we draw maps for the entire zone of an indoor distribution substation. The results were compared with the maximum permissible limits by national and international standards and we found that they were not exceeded. However, in all five areas the values of the magnetic field were above the threshold of 400 nT taking into account long-term exposure, which can lead to biological effects on health, especially for children.