Abstract-Earlier studies have shown that the occupational exposure of electric fields at 400 kV substations can be higher than the low action level of 10 kV/m set by the Directive 2013/35/EU. One possibility for decreasing the occupational exposure is to surround the worker with a Faraday cage. The objective of the study was to investigate how effective a Faraday cage is in decreasing the ELF electric field exposure during work tasks from a man hoist at a 400 kV substation. First, we measured the electric field exposure while performing maintenance tasks from a man hoist. We then constructed a Faraday cage around the man hoist and measured the exposure again, with hopes that the exposure would be sufficiently reduced to create a safe working environment. The Faraday cage was constructed from a steel net 0.5 m in width with 19-mm meshes. The net was made of hotdip galvanized steel wire, 1.0 mm in diameter. The net and the man hoist were then grounded. The maximum electric field without the cage was 28.8 kV/m, and with the cage, it was 0.5 kV/m. The electric field, therefore, was decreased by 96.8-99.9%, validating the efficacy of Faraday cages.

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Various guidelines for the protection of human beings against possible adverse effects resulting from exposure to electromagnetic fields (EMFs) have been published with a view towards continual improvement; therefore, decreasing exposure is an important research area. The aim of this study was to investigate the possibility of decreasing electric field exposure with arc flash rated personal protective equipment (PPE), which in this case was a set of coveralls, and to compare the measurement results to calculations using the helmet-mask measuring system. We collected the data under a 400-kV power line. The test person stood on isolated aluminum paper, and the current between the ground and the aluminum paper was measured. When the test subject wore the arc flash PPE, the current to the ground was only 9.5% of the current measured when wearing normal clothes, which represents a clear decrease in exposure.

Directive 2013/35/EU of the European Parliament and Council, among other things, sets values for the occupational exposure of workers regarding the health and safety risks arising from electromagnetic fields. In order to ensure worker safety, the Finnish national grid operator, Fingrid Oyj, conducted several measurements of electromagnetic fields at its substations. One of the goals of the measurements was to ensure that a magnetic flux density of 1000 µT (rms), set as the lower action value by the EU directive, was not reached in any location accessible to substation workers. The highest magnetic flux densities at substations can be found near shunt reactors and their cables, which is why the measurements were focused on those areas. The lower action value of 1000 µT (rms) was surpassed at two locations. This discovery led to immediate actions to prevent workers from accessing these locations.

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