For some years, the Italian Regional Agencies for Environmental Protection 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.
                                    多年来,意大利地区环境保护机构一直致力于评估靠近电源线的接收器长期暴露于 50 Hz 磁场的情况。在这项研究中,建议了经验和程序,以便估计不同电力线同时产生磁感应情况下的长期暴露
水平。在最简单的情况下,通过验证每条线路中的电流变化与测量的磁感应强度之间的相关系数来评估单条线路的影响。当单条线路的流行情况不明确且系统化时,必须考虑许多附加数据(电压、电流、相位和几何配置)。描述了位于利沃诺的一所学校靠近两条线且放置在相同支撑物上的情况,并给出了最可能的暴露值的范围,对应于两个电流通量的相位变化。