Occupational exposure to electric fields remains within acceptable range in 400 kV substations
Researchers at Tampere University of Technology (TUT) have investigated the current densities that are induced in the human body as a result of occupational exposure to electric fields in the vicinity of 400 kilovolt substations and power lines.The research is related to the EU’s proposed directive that protects workers from the potentially adverse health effects of electromagnetic (EMF) fields. The directive aims to establish minimum EMF safety standards across all the member states of the EU. The exposure limits are based on guidelines issued by the International Commission on Non-Ionizing Radiation Protection (ICNIRP).
“The current densities induced in the human body were defined based on extensive measurements conducted by my research group. The results confirmed that workers’ exposure to electric fields in 400 kV substations and power lines does not exceed the limit specified in the original directive dating back to 2004,” says Professor Leena Korpinen from the Department of Electronics and Communications Engineering at TUT. She was in charge of overseeing the research project.
However, the EU decided to postpone the implementation of the original directive and ICNIRP subsequently updated its recommended exposure limits. As a result, the proposed directive was amended and the latest draft sets forth restrictions concerning the strength of the electric field induced in living tissue and not the current density. The measurement methods used by researchers at TUT were not applicable for determining the strength of internal electric fields.
“Electric fields induce a current and an internal electric field in the human body. We can measure the current but not the internal electric field, which has to be calculated”, says Korpinen.
As a welcome addition to Professor Korpinen’s research group, Professor Hiroo Tarao from Japan joined the group for a year. Tarao specializes in electric field calculation. He reviewed the measurement data generated by the research group and calculated the strength of the internal electric fields using a realistic human model. Tarao’s calculations demonstrated that the strength of the fields falls below the recommended exposure limits specified by ICNIRP.
A research paper that presents both the measurement results of TUT’s research group and the calculations performed by Professor Hiroo Tarao was recently published in the Bioelectromagnetics journal.
The research project was launched in 2005, primarily to explore the electric field exposure of substation and power line workers and the current densities induced in the human body. During two summers, the research group completed 151 measurements in Fingrid Oyj’s 400 kilovolt substations and near 110, 220 and 400 kilovolt power lines. The measurements were sponsored by Fingrid Oyj. The researchers used new measurement methods that were developed in collaboration with industry partners.
Further information:
Tampere University of Technology, Department of Electronics and Communications Engineering
Professor Leena Korpinen, tel. +358 40 595 2035, leena.korpinen@tut.fi
Hiroo Tarao, Leena H. Korpinen, Harri A. Kuisti, Noriyuki Hayashi, Jarmo A. Elovaara, Katsuo Isaka. Numerical evaluation of currents induced in a worker by ELF non-uniform electric fields in high voltage substations and comparison with experimental results, Bioelectromagnetics, Volume 34 Issue 3 (January 2013) p. 61- 73 http://onlinelibrary.wiley.com/doi/10.1002/bem.21738/pdf