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Over the recent years some countries have introduced norms, regulations or recommendations limiting the value of few A/m permissible levels of the 50 Hz magnetic field (MF) in the environment. This results from the studies indicating a number of biological effects on living organisms exposed to magnetic fields with levels similar to those produced by high voltage overhead power lines. The main objective of these restrictions was to protect human health from the effects of MF produced by high voltage overhead transmission lines. The changed permissible level of MF intensity to the level now binding in different countries will have great economic and financial impact. The greatest impact will be observed in the already established residential areas, which require that the levels of magnetic field from existing overhead lines be lowered. The effects of more strict regulations on the protection against the effects of the 50 Hz magnetic field, reducing the levels to values lower than 0.25 A/m, can be grouped into three categories: technical effects, space and landscape implications and financial impact. The lowering of MF maximum acceptable level will require changes in the structure of new power lines and modifications in the existing grid. Unfortunately, the replacing of overhead power lines with cables is not possible on account of too high costs. The extension of the area, in which construction of dwelling houses will not be possible, can turn out to be the only solution.

Identification of electromagnetic fields in the vicinity of high voltage overhead transmission lines requires taking measurements and determining, on their basis, the maximum values of electric (Emax) and magnetic (Hmax) field strength, as well as the width of the area with electric field strength exceeding 1 kV/m. Measurements should be carried out in the places, where the distance between phase wires and the ground is smallest, and their results converted to conditions expected at the most disadvantageous parameters of the work of line in terms of their effect on the environment. This requires taking into consideration the maximum voltage of the transmission line, as well as the highest acceptable temperature of wires. In a single-circuit line, convertion of the measured values to expected maximum values of Emax and Hmax is not difficult, although it requires knowledge of cross-profiles in spans, in which measurements were taken. However, recounting the values of magnetic field strength produced by two-circuit lines creates a serious problem. Since in the majority of cases, the measurements in the surrounding of two-circuit lines are carried out at asymmetrical currents in both circuits, converting their results to symmetrical currents of the lines is practically impossible. Therefore, the results of the measurements of magnetic field strength carried out at the asymmetrical current of a two-circuit line cannot provide the basis for assessing the possibility of exceeding the allowable value of magnetic field intensity determined in the binding regulations. Such an assessment can only be done on the basis of the results of relevant calculations.

This paper presents some situations, in which measurements of electromagnetic fields generated by transmission lines and substations should be performed. The range of measurements may differ, but maximum values of electric and magnetic fields and flux density must be identified in all situations. The area with electric field exceeding 1 kV/m should be identified as well. The author also presents basic requirements to be met by the measurement technique. These requirements are specified according to the national standard. Special attention should be paid to the identification of the spatial distribution of electric field and flux density generated in the vicinity of high voltage transmission lines. To verify the measurement results, it is necessary to calculate the distribution of both aforesaid field components. For environmental protection purposes, it is also proposed that the report should include measurements of electromagnetic fields of 50 Hz along with calculated results presented in tables and diagrams.

The localization of high voltage objects, e.g., overhead transmission lines, under the spatial planning and environmental protection regulations is discussed. The most important elements of the localization procedure concerning high voltage overhead lines are presented. One of the elements of this procedure is the assessment of the investment environmental impact. The environmental audit is an essential document, in which this impact is described. It seems that its scope specified in the Environmental Protection Act is not adjusted to the specificity of line investments. This gives rise to some problems in preparing environmental audits for overhead lines, e.g., possible influence of high voltage lines on the Natura 2000 area zones. Several other related problems are also highlighted in this paper.

This paper presents the most important elements of the localization procedure of high voltage overhead lines and substations and radiocommunication objects which are the source of electromagnetic fields. These fields are perceived as a major threat to human health. The point of departure to make a choice of investments is the special classification of technical installations described in one of the executive directive issued by virtue of the Environmental Protection Act. This special executive directive enumerates a lot of technical objects (installation), classified in the group of investments which have significant impact on the environment and some objects which could be classified in this group. For all this technical installations (e.g., overhead high voltage power lines) the provisions of the Environmental Protection Act impose an obligation to take particular steps to assure transparency of the environmental protection procedures, transborder procedures and the protection of areas included in the Natura 2000 network.

Thirty five volunteers had their conscious reaction to sound and light stimuli measured at an experiment under the conditions approximating those near overhead high voltage lines. The short-term electrical field of 50 Hz frequency and intensity exceeding the 10 kW/m value was found to prolong the reaction for both types of stimuli applied. The electrical field of 4.4 kW/m intensity did not evoke any significant changes. The pathomechanism of those disturbances is being discussed.