Keywords

1 General

The electricity has many benefits in our daily life. But generating, transmitting, distributing and using electricity can expose people to ELF-EMFs, which interact with the human body by mainly inducing electric currents in it. During the past decades, a lot of research has been devoted to investigation of possible health effects of exposure to ELF-EMFs, including childhood and adult cancers, reproductive dysfunctions, cardiovascular and developmental disorders, immunological modifications, neurological effects, etc. Particularly, a (poor) statistical link between childhood leukemia and prolonged exposure to residential ELF magnetic fields higher than 0.3–0.4 μT has been reported by a number of epidemiological studies [1, 2]. In 2002, based on these findings, the International Agency for Research on Cancer (IARC)—an intergovernmental agency activating within the World Health Organization (WHO)—has concluded that the ELF magnetic fields are “possibly carcinogenic to humans” (Group 2B carcinogens, designating agents for which the evidence in humans is limited and the evidence in animals is “less than sufficient”). As for ELF electric fields, IARC has concluded that they are “unclassifiable as to carcinogenicity in humans” (Group 3 carcinogens) [3].

Aiming at preventing the established health effects associated with short-term exposure to high intensity ELF-EMFs, principally induced currents, ICNIRP and IEEE (the Institute of Electrical and Electronics Engineers) have formulated exposure guidelines in 1998 [4] and 2002 [5], respectively. According to the scientific information currently available, long-term exposure to ELF field levels not exceeding the limits prescribed by these guidelines is considered safe for the purpose of protecting human health. There is no established evidence that exposure to ELF-EMFs emitted by power lines, substations, transformers or other electrical equipment, regardless of the proximity, can cause any known health effects. But there is a continuous debate as to what might be adequate precautionary approaches at these lower field levels. Furthermore, the general public often expresses concern about ELF-EMFs, especially in relation with setting up new overhead high-voltage power lines or living in their vicinity [6,7,8,9].

The OHVPLs are considered significant sources of both electric and magnetic fields. Both fields are strongest directly under the OHVPL and sharply reduce with distance from it. Of course, in addition to distance, there are many other factors influencing the ELF-EMFs originating from OHVPLs, including voltage, current, phasing, ground clearance, observation height above the ground, balance within circuit, balance between circuits, conductor bundle, existence of parallel lines, ground resistivity (conductivity), etc. Moreover, the electric fields are greatly attenuated by buildings, walls, fences, trees and other obstacles in the neighborhood, but the magnetic fields pass through most materials and cannot be attenuated as easily as the electric fields [10,11,12].

To determine ELF electric and magnetic field levels emitted by OHVPLs and to assess compliance with relevant exposure limits, both measurements and computations can be performed [13,14,15,16,17,18,19]. Computations are often preferable to measurements because they can be conducted for any desired exposure scenario rather than being confined to the particular conditions at the time of taking measurements. Analytical and numerical methods can be used for computations, usually employing two-dimensional (2D) models because of their simplicity [20,21,22,23,24,25,26,27,28,29,30,31,32,33]. Very often, the numerical calculations (simulations) exploit the finite element method (FEM), which is recognized for its ability to generate accurate 2D electric and magnetic field distributions in the transverse section of the OHVPLs and of other power–frequency systems [19, 29,30,31,32,33].

In this chapter, a simple and yet effective FEM approach is proposed to compute and analyze—from the perspective of public exposure—ELF electric and magnetic fields produced by typical configurations of OHVPLs belonging to the Romanian power grid. Computations are performed with ANSYS Maxwell 2D electromagnetic simulation software, mainly in the form of RMS electric field strength and RMS magnetic flux density lateral profiles, at the standard height h = 1 m above the ground level. It is worthwhile to remark that Romania, as a member of the European Union (EU), has implemented exposure limits derived from the Council Recommendation of 12 July 1999 on the limitation of exposure of the general public to electromagnetic fields (0 Hz–300 GHz) [34], which is based on the guidelines issued by ICNIRP in 1998. For power–frequency electric and magnetic fields, these limits are 5000 V/m and 100 μT, respectively.

From this point, the chapter is organized as follows. First, a 2D ANSYS Maxwell model for computing ELF electric and magnetic fields around OHVPLs will be developed and validated against simulation software based on analytical methods. Next, it will be used to investigate exposure to ELF-EMFs generated by a selection of OHVPLs with nominal voltages of 110, 220 and 400 kV. As already mentioned, special attention will be given to the field distribution at 1 m height above the ground, taking into consideration influencing factors such as loading, phasing and ground clearance. Compliance with the ICNIRP exposure limits for general public will be assessed for each particular case.

2 2D ANSYS Maxwell Model for Computing ELF Electric and Magnetic Fields Around OHVPLs

ANSYS Maxwell 2D is a high-performance low frequency electromagnetic field simulation software that uses the finite element method for solving electric, magnetostatic, eddy current and transient problems. Therefore, it may serve as an appropriate tool for computing exposure to ELF-EMFs originating from OHVPLs, but such investigations are rather rare and mostly focused only on the magnetic field exposure [17, 35, 36]. As an extension of a recent study by the authors [11], this section presents the development and validation of a 2D Maxwell model for computing both electric and magnetic fields emitted by various OHVPLs. The model is implemented for a common configuration of 110 kV double-circuit line used for primary power distribution, but it can easily be applied to any other OHVPL. The model validation is achieved against previously developed software based on quasi-static analytical methods.

2.1 Model Development

The 110 kV double-circuit OHVPL selected for model implementation—often found in the proximity of urban settings—has geometry dictated by suspension towers of Sn 110.252 type, as illustrated in Fig. 1. The phases of the two circuits are realized with Aluminum Conductor Steel-Reinforced (ACSR) cables of Sect. 240/40 mm2 (21.7 mm exterior diameter), while the shield wire (SW) is represented by a 160/95 mm2 ACSR conductor (20.75 mm exterior diameter). The OHVPL is considered to operate at a load of 500 A (close to the maximum rated current), with the phases of the two circuits perfectly balanced. In addition, because the field level largely depends on the relative phasing between the two circuits, we assumed both untransposed (ABC/A’B’C’) and directly transposed (ABC/C’B’A’) phase arrangements, which clearly determine the maximum and minimum exposure to the sides of the line [37, 38], where people are most likely to live or spend time.

Fig. 1
figure 1

Suspension tower of Sn 110.252 type (dimensions are given in mm)

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  1. a.

    FEM geometric model

The global FEM geometric model is presented in Fig. 2, where the considered 110 kV double-circuit OHVPL is placed above a ground with the electrical conductivity of 0.01 S/m, the relative electric permittivity of 10 and the relative magnetic permeability of 1. The ground clearance, namely 9 m, corresponds to an “average height” of the OHVPL above the ground, calculated as havg = hmax—(2/3)·f [39], where hmax = 15.2 m represents the maximum height of the conductors (at tower) and f = 9.2 m is the conductors sag. The active conductors are modeled as presented in Fig. 3, as simple aluminum cylinders with the electrical conductivity of 3.8·107 S/m, the relative electric permittivity of 1 and the relative magnetic permeability of 1, while the influence of the SW on the electric and magnetic field distribution is ignored (the SW is not included in simulation). The applied boundary conditions are of Balloon type, which models the region outside the defined space as extending to infinity. The radius of the bounded region is taken R = 200 m, sufficiently large to determine the behavior of the two fields well outside the power line corridor, even for OHVPLs with higher nominal voltages. All simulations conducted in this study assume a total number of mesh elements of 1,223,286, but it can be lowered for more rapid and yet satisfactory analyzes.

Fig. 2
figure 2

Global FEM geometric model of the 110 kV double-circuit OHVPL

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Fig. 3
figure 3

Discretized OHVPL region

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  1. b.

    Magnetic field calculation

The magnetic field distribution around the OHVPL is obtained using the eddy current solver, which allows calculating magnetic fields that oscillate with a frequency (in this case, 50 Hz). However, because the magnetic field distributions generated with this solver are reported in terms of instantaneous magnetic flux density values over a 20 ms period, further post-processing is necessary to generate RMS magnetic flux density (lateral) profiles at the height h = 1 m, as often used for assessing exposure to ELF-EMFs from overhead power lines. Consequently, multiple instantaneous magnetic flux density profiles have been imported into Microsoft Excel, where they have been processed in a point-by-point fashion, according to the formula [11]:

$$B_{RMS} \left( i \right) = \sqrt {\frac{1}{N}\sum\limits_{n = 1}^{N} {B_{n}^{2} \left( i \right)} } ,$$
(1)

where B1(i), …, BN(i) represent the instantaneous values of the magnetic flux density corresponding to the point i of the profile and N = 73 is the total number of values.

Fig. 4
figure 4

Instantaneous magnetic flux density profiles at h = 1 m, for U phasing

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Figure 4 presents instantaneous magnetic flux density profiles obtained for untransposed (U) phasing, while Fig. 5 shows similar profiles obtained for transposed (T) phasing. The correspondent RMS magnetic flux density profiles—computed with Eq. (1)—are comparatively presented in Fig. 6. Starting at a certain distance from the centerline, any other phase arrangement will generate an RMS magnetic flux density profile between these two limit plots.

Fig. 5
figure 5

Instantaneous magnetic flux density profiles at h = 1 m, for T phasing

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Fig. 6
figure 6

Comparison between RMS magnetic flux density profiles obtained for untransposed and transposed phasing

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Figures 7 and 8 illustrate the magnetic field distribution around the OHVPL at the time instants corresponding to the maximum field profiles in Figs. 4 and 5, respectively. As evident, an extra degree of cancellation between the magnetic fields generated by the two circuits can be observed for transposed phasing. The distance from the centerline is 30 m in both distributions.

Fig. 7
figure 7

The magnetic field distribution around the 110 kV double-circuit OHVPL for U phasing (t = 10.83 ms)

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Fig. 8
figure 8

The magnetic field distribution around the 110 kV double-circuit OHVPL for T phasing (t = 11.66 ms)

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  1. c.

    Electric field calculation

The electric field distribution around the OHVPL is determined using the AC conduction solver, which allows calculating sinusoidally-varying electric fields (here, varying at 50 Hz). And this time, to generate RMS electric field strength lateral profiles at the height h = 1 m, multiple profiles of instantaneous electric field strength have been imported into Microsoft Excel, where they have been processed in the same way, by applying the formula [11]:

$$E_{RMS} \left( i \right) = \sqrt {\frac{1}{N}\sum\limits_{n = 1}^{N} {E_{n}^{2} \left( i \right)} }$$
(2)

where E1(i), …, EN(i) represent the instantaneous values of the electric field strength corresponding to the point i of the profile and N = 73 is the total number of values.

As in the case of magnetic field, Fig. 9 gives instantaneous electric field strength profiles obtained for U phasing, while Fig. 10 shows profiles obtained for T phasing. The two associated RMS electric field strength profiles—computed with Eq. (2)—are compared in Fig. 11.

Fig. 9
figure 9

Instantaneous electric field strength profiles at h = 1 m, for U phasing

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Fig. 10
figure 10

Instantane-ous electric field strength profiles at h = 1 m, for T phasing

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Fig. 11
figure 11

Comparison between RMS electric field strength profiles obtained for untransposed and transposed phasing

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Figures 12 and 13 illustrate the momentary distribution of the electric field around the OHVPL corresponding to the maximum field profiles in Figs. 9 and 10, respectively. Once again, an extra degree of cancellation between the electric fields generated by the two circuits can be observed for transposed phasing. As in the case of magnetic field, the distance from the centerline is 30 m in both distributions.

Fig. 12
figure 12

The electric field strength distribu-tion around the 110 kV OHVPL for U phasing (t = 10.55 ms)

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Fig. 13
figure 13

The electric field strength distribu-tion around the 110 kV OHVPL for T phasing (t = 20 ms)

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2.2 Model Validation

The model validation has mainly been performed with the help of two interactive software tools based on analytical methods, PowerELT and PowerMAG [28], which are capable to produce accurate electric and magnetic field (lateral) profiles at any user-defined height above the ground level, together with 2D electric and magnetic field distributions in the transverse section of the OHVPL, in any rectangular plotting area also defined by user. Assuming the same power line geometry, and voltage and current information (amplitude and phase, respectively), Fig. 14 compares RMS magnetic flux density profiles computed with the developed 2D ANSYS Maxwell model and PowerMAG software. Similarly, Fig. 15 compares RMS electric field strength profiles computed with the developed 2D ANSYS Maxwell model and PowerELT software. As obvious, there is an excellent agreement between numerical and analytical results, regardless the phasing (U or T).

Fig. 14
figure 14

Comparison between RMS magnetic flux density profiles obtained by numerical simulation and analytical computation

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Fig. 15
figure 15

Comparison between RMS electric field strength profiles obtained by numerical simulation and analytical computation

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Similar comparisons have also been made for OHVPLs with higher nominal voltages (i.e., larger physical dimensions), each time obtaining perfect matching between simulated profiles. Exposure to ELF-EMFs from some of these lines, under various conditions, will be discussed in the subsequent section.

3 Finite Element Analysis of ELF-EMFs from Typical OHVPLs Used in the Romanian Power Grid

In Romania, OHVPLs are used for both power transmission and power distribution. Power transmission is achieved through a total length of 8759.4 km of OHVPLs, of which [40]: 3.1 km—750 kV, 4915.2 km—400 kV, 3875.6 km—220 kV and 40.4 km—110 kV, where 482.6 km serves as interconnection lines. In addition, power distribution operators make use of more than 20,000 km of OHVPLs operating at 110 kV. Thus, for assessing exposure to ELF-EMFs emitted by these OHVPLs, we have selected two double-circuit lines with nominal voltages of 110 kV and 220 kV, respectively, and a single-circuit line with nominal voltage of 400 kV, which can be considered typical. Finite element analysis of ELF-EMFs from these lines assumes the same conditions as in the described model, except that computations will be performed for three different ground clearances (minimum, average and maximum), as well as for maximum allowable current. However, because of the direct proportionality between current and magnetic flux density, the computed fields can easily be scaled down for more common loads.

3.1 ELF-EMFs from the 110 kV Double-Circuit OHVPL

In essence, the 110 kV double-circuit OHVPL subjected to investigations is the same used for model development, which has geometry dictated by suspension towers of Sn 110.252 type. As already mentioned, the two circuits are realized with standard 240/40 mm2 ACSR conductors (21.7 mm exterior diameter), which have a maximum allowable current of 575 A (RMS). All other input data for this line are presented in Table 1, where di is the lateral distance from the OHVPL centerline to the conductor i, hi represents the height of the conductor i and hg denotes the ground clearance of the line: 6 m, 9 m and 15.2 m, respectively.

Table 1 Input data for the 110 kV double-circuit OHVPL using towers of Sn 110.252 type (untransposed phasing)
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  1. a.

    Magnetic field distribution

Figure 16 presents RMS magnetic flux density profiles at the height h = 1 m, for untransposed phasing. The maximum magnetic field beneath the line (not necessarily at the centerline) varies from 5.48 μT for hg = 15.2 m (at tower) to 18.5 μT for hg = 6 m (at mid-span), which is generally below 18.5% of the ICNIRP limit for general public, 100 μT. For transposed phasing (Fig. 17), the maximum magnetic field beneath the line varies from 2.12 μT for hg = 15.2 m to 16.1 μT for hg = 6 m, hence not exceeding 16.1% of the ICNIRP exposure limit. As it can easily be observed, starting with some distance from the centerline, the transposed phasing produces much lower magnetic field levels.

Fig. 16
figure 16

RMS magne-tic flux density profiles for the 110 kV OHVPL, for untrasnsposed phasing and various ground clearances

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Fig. 17
figure 17

RMS magne-tic flux density profiles for the 110 kV OHVPL, for transposed phasing and various ground clearances

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Considering the average clearance hg = 9 m and a (more) typical loading of 325 A, Table 2 gives magnetic field levels at various distances from the centerline. Beneath the line, the magnetic flux density does not exceed 6.51 μT for U phasing and 4.03 μT for T phasing, while at the edge of the OHVPL corridor—18.5 m from the centerline, according to national regulations [41]—it decreases to 2.32 μT and 0.73 μT, respectively. The critical value of 0.4 μT—often used in epidemiological studies—is reached at a lateral distance of about 53.9 m and 24.5 m, respectively.

Table 2 Typical magnetic field levels from the 110 kV OHVPL (hg = 9 m, I = 325 A)
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  1. b.

    Electric field distribution

The RMS electric field strength distribution at the height h = 1 m—for untransposed phasing—is illustrated in Fig. 18. The maximum electric field beneath the line (at the centerline) varies from 882.8 V/m at tower to 3017.2 V/m at mid-span, which is generally below 60.34% of the ICNIRP exposure limit for general public, 5000 V/m. For transposed phasing (Fig. 19), the maximum electric field levels beneath the line range from 243.2 V/m at tower to 1790.2 V/m at mid-span, hence not exceeding 35.8% of the exposure limit.

Fig. 18
figure 18

RMS electric field strength profiles for the 110 kV OHVPL, for untransposed phasing and various ground clearances

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Fig. 19
figure 19

RMS electric field strength profiles for the 110 kV OHVPL, for transposed phasing and various ground clearances

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For the average clearance hg = 9 m (Table 3), the electric field strength beneath the line reaches 1901.8 V/m for U phasing and 784.4 V/m for T phasing, while the electric field strength at the corridor edge reaches 110.3 V/m and 109.5 V/m, respectively. At the distance of 50 m from the centerline route, the electric field levels fall to only 77 and 11.3 V/m, respectively, similar to the lowest levels measured at 30 cm distance from household appliances.

Table 3 Typical electric field levels from the 110 kV OHVPL (hg = 9 m)
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3.2 ELF-EMFs from the 220 kV Double-Circuit OHVPL

The 220 kV double-circuit OHVPL selected for FE analysis has geometry dictated by suspension towers of Sn 220.202 type. The line is equipped with standard 450/75 mm2 ACSR conductors (29.25 mm exterior diameter), for which the maximum allowable current is 975 A. Table 4 presents the geometrical data, as well as the voltage and current information used for computation, where the ground clearance hg is taken 7 m, 11 m and 19 m, respectively. Because the geometry of this line is quite similar to the geometry of the 110 kV line, we expect similar electric and magnetic field distributions.

Table 4 Input data for the 220 kV double-circuit OHVPL using towers of Sn 220.202 type (untransposed phasing)
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  1. a.

    Magnetic field distribution

For untransposed phasing (Fig. 20), the maximum RMS magnetic flux density beneath the 220 kV OHVPL ranges from 7 μT at tower to 23.9 μT at mid-span, generally accounting for less than 24% of the ICNIRP exposure limit for general public. For transposed phasing (Fig. 21), the maximum RMS magnetic flux density along the half-span varies between 3.62 and 24.33 μT, hence not exceeding 24.4% of the ICNIRP exposure limit. And this time, much lower field levels can be observed at larger distances from the line for T phasing.

Fig. 20
figure 20

RMS mag-netic flux density profiles for the 220 kV OHVPL, for untransposed phasing and various ground clearances

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Fig. 21
figure 21

RMS mag-netic flux density profiles for the 220 kV OHVPL, for transposed phasing and various ground clearances

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Table 5 gives magnetic field levels at various distances from the OHVPL centerline for the average clearance hg = 11 m and a (more usual) loading of 200 A. Beneath the line, the magnetic flux density does not exceed 2.87 μT for U phasing and 2.35 μT for T phasing, while at the edge of the OHVPL corridor—27.5 m from the centerline [41]—it decreases to 0.93 μT and 0.42 μT, respectively. The critical value of 0.4 μT is reached at a lateral distance of about 45 m and 25.4 m, respectively. As we can see, because of the low load conditions, the typical exposure levels from this line are lower than those associated with the 110 kV OHVPL.

Table 5 Typical magnetic field levels from the 220 kV OHVPL (hg = 11 m, I = 200 A)
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  1. b.

    Electric field distribution

The electric field strength distribution for untransposed phasing is illustrated in Fig. 22. Beneath the 220 kV double-circuit OHVPL, the maximum field strength at the standard height h = 1 m ranges from 1452.8 V/m for hg = 19 m to 4673.7 V/m for hg = 7 m, which is very close to the ICNIRP limit for general public (93.5% of the limit). For transposed phasing (Fig. 23), the maximum electric field strength at the same height lies in the range from 499.2 to 3653.9 V/m, which is below 73.1% of the ICNIRP exposure limit.

Fig. 22
figure 22

RMS electric field strength profiles for the 220 kV OHVPL, for untransposed phasing and various ground clearances

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Fig. 23
figure 23

RMS electric field strength profiles for the 220 kV OHVPL, for transposed phasing and various ground clearances

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For the average clearance hg = 11 m (Table 6), the electric field strength beneath the line reaches 2969.5 V/m for U phasing and 1580 V/m for T phasing, while the electric field strength at the corridor edge (27.5 m from the centerline) only reaches 215.9 V/m and 160 V/m, respectively. At 50 m from the OHVPL centerline, the electric field strength diminishes to 167.1 V/m and 40 V/m, respectively. As in the case of the 110 kV single-circuit OHVPL, such levels can also be measured at a distance of 30 cm from household appliances.

Table 6 Typical electric field levels from the 220 kV OHVPL (hg = 11 m)
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3.3 ELF-EMFs from the 400 kV Single-Circuit OHVPL

The last OHVPL selected for FE analysis is a 400 kV single-circuit line with geometry dictated by anchor portal towers of PAS 400.102 type. The line is equipped with two standard 450/75 mm2 ACSR conductors per phase, with a distance between individual conductors of 0.4 m. The input data for this line are presented in Table 7, where the ground clearance hg is taken 8.2 m, 12.6 m and 21.4 m, respectively. Magnetic field computations assume a maximum current of 1950 A.

Table 7 Input data for the 400 kV single-circuit OHVPL using towers of PAS 400.102 type
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  1. a.

    Magnetic field distribution

The RMS magnetic flux density distribution at the height h = 1 m is illustrated in Fig. 24. As with the other investigated OHVPLs, the magnetic field beneath the 400 kV line does not exceed the ICNIRP exposure limit for general public, but at mid-span it can be as high as 57.4 μT, which represents more than half of this limit. Towards the tower, it falls to only 14.85% of the limit.

Fig. 24
figure 24

RMS mag-netic flux density profiles for the 400 kV OHVPL, for various ground clearances

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Once again, Table 8 gives magnetic field levels at various distances from the OHVPL centerline for the average clearance hg = 12.6 m and a (normal) loading of 450 A. As it can easily be observed, the magnetic flux density at the OHVPL centerline is 7.73 μT, while at the edge of the OHVPL corridor—37.5 m from the centerline [41] —it decreases to only 1.22 μT. The critical value of 0.4 μT is reached at a lateral distance of about 65.1 m.

Table 8 Typical magnetic field levels from the 400 kV OHVPL (hg = 12.6 m, I = 450 A)
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  1. b.

    Electric field distribution

The RMS electric field strength distribution at the height h = 1 m is illustrated in Fig. 25. This time, the electric field at mid-span (hg = 8.2 m) is about two times higher than the ICNIRP exposure limit for general public, namely 9145.3 V/m. Towards the tower (hg = 21.4 m), the electric field strength falls to 1970.9 V/m (39.41% of the limit), but, as the ground clearance increases, the maximum field levels slightly move outside the line (for hg = 21.4 m, the maximum field strength is recorded at a distance of 16 m from the OHVPL centerline).

Fig. 25
figure 25

RMS electric field strength profiles for the 400 kV OHVPL, for various ground clearances

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Finally, Table 9 gives electric field levels for the average clearance hg = 12.6 m. The electric field strength beneath the line reaches 4752 V/m, decreasing to 776.4 V/m at the corridor edge (37.5 m from the OHVPL centerline) and to 340.2 V/m at 50 m from the OHVPL centerline. At 100 m lateral distance, the electric field drops drastically, to only 44.1 V/m.

Table 9 Typical electric field levels from the 400 kV OHVPL (hg = 12.6 m)
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  1. c.

    Alternative computation approach

All computations performed above assume that each sub-conductor of the considered 400 kV single-circuit OHVPL is modeled separately. However, this model can be simplified by replacing each of the three bundled conductors with an equivalent conductor of radius Req, given by [42]:

$$R_{eq} = \sqrt[N]{{R \cdot d^{{\left( {N - 1} \right)}} }},$$
(3)

where N stands for the number of sub-conductors in bundle, R represents the radius of a sub-conductor and d is the separation distance between sub-conductors. Equation (3) is applicable for up to three conductors per bundle, in our case leading to Req = 76.485 mm.

Figure 26 compares RMS magnetic flux density profiles computed with ANSYS Maxwell 2D by both approaches, as well as with PowerMAG software, which makes use of equivalent conductor model. As it can be observed, there is an excellent agreement between the three magnetic field profiles.

Fig. 26
figure 26

Comparison between RMS magnetic flux density profiles obtained by the two approaches with ANSYS Maxwell 2D and PowerMAG software (hg = 12.6 m, I = 450 A)

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Similarly, Fig. 27 compares RMS electric field strength profiles computed with ANSYS Maxwell 2D by both approaches, as well as with PowerELT software, which also makes use of equivalent conductor model. And this time, an excellent agreement between the three electric field profiles can be observed.

Fig. 27
figure 27

Comparison between RMS electric field strength profiles obtained by the two approaches with ANSYS Maxwell 2D and PowerELT software (hg = 12.6 m)

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4 Conclusions

This chapter has been devoted to computing and analyzing ELF electric and magnetic fields emitted by typical configurations of OHVPLs used in Romania. All computations have been conducted using a 2D ANSYS Maxwell finite element model, strictly verified by quasi-static analytical methods. According to the obtained results, the highest exposure levels to ELF electric fields are associated with the 400 kV OHVPLs, directly beneath the line approaching the double of the ICNIRP limit for general public. As for ELF magnetic fields, the highest exposure levels are also associated with the 400 kV OHVPLs, but they are approaching only 60% of the ICNIRP limit. At the edge of the line corridor, the typical ELF electric and magnetic fields originating on the investigated OHVPLs are well below the specified limits, regardless the nominal voltage of the line. The computed ELF-EMF exposure levels are in line with those determined for similar OHVPLs in other countries.