Evaluation of long-term exposure to the magnetic field produced from power lines

For some years, the Italian Regional Agencies for Environmental Protection (ARPA) have been engaged in the evaluation of long-term exposure to 50 Hz magnetic fields for receptors close to power lines. In this study, experiences and procedures are suggested in order to estimate long-term exposure levels in the case of magnetic induction produced contemporaneously by different power lines. In the simplest cases. the influence, of a single line is evaluated by verifying the correlation factor between the variation of the current in each line and the measured magnetic induction. When the prevalence of a single line is not clear and systematic, much additional data (voltage, current, phases and geometrical configuration) have to be considered. The case of a school in Livorno near two lines, placed on the same supports, is described and a range of the most probable exposure values is given, corresponding to the phase change of the two current fluxes.