In this preliminary study, the human perception of static electric fields, alternating electric fields and their co-exposure should be investigated and factors that influence the perception should be determined.
As part of the energy transition in Germany, high-voltage direct current (HVDC) lines producing static electric fields are in planning. However, the human perception of static electric fields was rarely investigated in the past. In the present preliminary study, the essential settings for a future comprehensive main study should be identified.
Eleven healthy participants (9 males and 2 females) aged 23 to 33 years were included in the randomized cross-over study. Two participants dropped out during the period of the experiments. Overall, 5 test days per participant were carried out. To investigate the influence of experimental and environmental factors on human electric field perception, the ramp slope of electric field buildup, exposure duration, ion current density, polarity, and relative humidity were modified on different test days.
|Exposure 1: 0 Hz|
|Exposure 2: 50 Hz|
|Exposure 3: 0–50 Hz|
|Chamber||the exposure lab was 4 m long and wide and 3 m high, and contained a central height‐adjustable chair; the room and the chair were built of laminated densified wood to prevent conductive processes and charge accumulation; relative humidity could be set to 30%, 50%, or 70%, whereas temperature was constantly kept at 22 °C (±0.2 °C); several measures were taken to guarantee real sham exposure conditions and the double‐blind study design; security measures were taken to prevent arc discharge and to ensure participant's safety|
|Setup||the electric field and ion current generating systems were located in the ceiling of the exposure lab and consisted of four high‐voltage electrodes; the electrodes were 4 m in diameter and mounted on top of each other; electrodes 1, 2, and 4 consisted of 2 mm‐thick perforated aluminum sheets, while electrode 3 was constructed of single high‐grade steel wires with a diameter of 200 μm and a distance of 0.1 m to each other.; whereas electrodes 2, 3, and 4 were used to generate a uniform ion current flow, electrode 1 was primarily used for electric field generation; fourteen grading electrodes positioned on top of each other on the exposure lab walls ensured a homogeneous electric field between electrode 1 and the floor, which was used as the base plate|
|Sham exposure||A sham exposure was conducted.|
Overall perception threshold was 23.4 kV/m for static electric fields, 16.9 kV/m for alternating electric fields and 11.4 kV/m for co-exposure, indicating that the averaged perception threshold for co-exposure to 4 kV/m alternating electric field and 6–30 kV/m static electric field was lower than that for the respective exposures alone. Relative humidity was identified as an environmental factor influencing the perception of static electric fields and alternating electric fields. An appropriate ramp slope and an exposure duration for future studies was elaborated. Subjective sensations evoked under exposure were individually different and attributed to various parts of the body; however, no participant reported painful sensations.
The authors concluded that several environmental and experimental factors influencing the human perception of electric fields and preliminary perception tresholds could be identified, which provide an essential basis for a large‐scale main study.