The aim of the study was to determine human detection thresholds for static (DC), alternating (AC), and hybrid electric fields (co-exposure to AC and DC EF; various DC EF strengths, constant AC EF strength).
The study was motivated by the ongoing changes in energy transmission with the newly introduced construction of both high-voltage alternating current (HVAC) and high-voltage direct current (HVDC) overhead power lines mounted on the same tower generating also hybrid electric fields. Despite this development, no limit values for static electric fields and hybrid electric fields are provided due to the lack of data. The study is based on the previous publication of the femu (Jankowiak et al. 2021).
A total of 203 healthy participants equally distributed over sex and four age groups between 20 and 79 years participated in the study. Each participant attended the experimental testing on one day from 8 a.m. to 4 p.m. The experimental task was carried out in 10 SDT sessions, each consisting of 40 trials with a duration of 15 min (in hybrid with ion sessions half of the trials), and 3 SIAM sessions with a variable duration between 5 and 20 min.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
0 Hz
Exposure duration:
20 s
|
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|
Exposure 2:
0 Hz
Exposure duration:
20 s
|
|
|
Exposure 3:
50 Hz
Exposure duration:
20 s
alternating electric field
|
|
|
Exposure 4:
0–50 Hz
Exposure duration:
20 s
|
|
|
Exposure 5:
0–50 Hz
Exposure duration:
20 s
|
|
| Frequency | 0 Hz |
|---|---|
| Type | |
| Exposure duration | 20 s |
| Additional info | static electric field |
| Exposure source | |
|---|---|
| Chamber | the exposure laboratory had dimensions of 4×4x3 m and contained a central height‐adjustable chair; the walls of the exposure lab were built of laminated densified wood to provide good electric insulation; the lab was placed on a sylomer layer to dampen external vibrations; relative humidity was set to 30%, 50%, or 70%; temperature was constantly kept at 22 °C (±0.2 °C); possible auditory signals from the electrodes were masked by a 65.8 dB (A) white noise; several safety measures were integrated to ensure participant's safety |
| Setup | electric fields and ion currents were generated by four 4×4 m electrodes stacked over each other at the ceiling of the exposure lab. Electrodes 1, 2, and 4 were made of perforated aluminum sheets, whereas, within electrode 3, 200 μm high-grade steel wires were mounted at a distance of 0.1 m; 14 grading electrodes positioned on top of each other on the lab walls ensured a homogeneous electric field between electrode 1 and the floor, which was used as the base plate; electrodes 2, 3, and 4 were used to generate a uniform ion current flow, electrode 1 was primarily used for electric field generation |
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| electric field strength | 4 kV/m | minimum | calibration | - | - |
| electric field strength | 44 kV/m | maximum | calibration | - | - |
| Frequency | 0 Hz |
|---|---|
| Type | |
| Exposure duration | 20 s |
| Additional info | static electric field + ion currents |
| Exposure source | |
|---|---|
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| electric field strength | 14 kV/m | minimum | calibration | - | - |
| electric field strength | 38 kV/m | maximum | calibration | - | - |
| cf. remarks | - | - | calibration | - | ion current densities 80, 200, 300 and 400 nA/m² |
| Frequency | 50 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | 20 s |
| Additional info | alternating electric field |
| Exposure source | |
|---|---|
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| electric field strength | 4 kV/m | minimum | calibration | - | - |
| electric field strength | 30 kV/m | maximum | calibration | - | - |
| Frequency | 0–50 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | 20 s |
| Additional info | hybrid electric field |
| Exposure source | |
|---|---|
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| electric field strength | 2 kV/m | minimum | calibration | - | static electric field |
| electric field strength | 44 kV/m | maximum | calibration | - | static electric field |
| electric field strength | 4 kV/m | - | calibration | - | alternating electric field |
| Frequency | 0–50 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | 20 s |
| Additional info | hybrid electric field + ion current |
| Exposure source | |
|---|---|
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| electric field strength | 18 kV/m | minimum | calibration | - | static electric field |
| electric field strength | 24 kV/m | maximum | calibration | - | static electric field |
| electric field strength | 4 kV/m | - | calibration | - | alternating electric field |
| cf. remarks | - | - | - | - | ion current density 10 nA/m² |
The results indicated that detection thresholds of hybrid electric fields were lower compared to single presentation of static or alternating electric fields. Ion current exposure enhanced electric field perception. High relative humidity facilitated static electric field perception, whereas low relative humidity reinforced the perception of alternating electric fields.
The authors concluded that human perception detection thresholds were provided for static, alternating and hybrid electric fields. They can help to improve the construction processes of energy transmission systems and the prevention of unwanted sensory perception.
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