DECREASING THE EXTREMELY LOW-FREQUENCY ELECTRIC FIELD EXPOSURE WITH A FARADAY CAGE DURING WORK TASKS FROM A MAN HOIST AT A 400 KV SUBSTATION

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 0.5m in width with 19-mm meshes. The net was made of hotdip galvanized steel wire, 1.0mm 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.