Technical Management Of The Electric And Magnetic Fields in Electric Power System
Keikko, Tommi (2003)
Tampere University of Technology
Sähkötekniikan osasto - Department of Elecrical Engineering
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Electric and magnetic fields from power systems have become an important issue. The reasons for this are public concern about the possible health risks the fields may cause and disturbances caused by the fields. The aim of this thesis was to develop a technical management chain. The thesis consists of an introductory part supplemented by eight international publications. Four cases were studied: power lines, electric substations, indoor distribution substations, and arc furnace.The methodological background of this thesis consists of theoretical background for boundaryvalue problems, measurements, mitigation methods and the methods for the four cases. Measurement methods were studied, to get reproducible measurements. Calculations were carried out from the same locations to get results comparable to measurements. Calculations were carried out with analytical methods, FEM and a combination of them. Mitigation methods for the cases were studied by calculations and especially with indoor distribution substations by measuring the same place before and after structural changes. A technical management chain was developed for general electric power systems and for four different management cases.For technical management of the fields with transmission lines, the mitigation methods have been widely presented in literature. However, new viewpoints present the effect of the vegetation and the effect of the line temperature, which affects the line height having a significant effect on the fields. Based on the study, the best mitigation methods for transmission lines are the line route design and attenuation with distance to the line.For technical management of the electric substations the occupational exposure is important, because the electric substation switchyards are forbidden areas to the public. One suitable mitigation method is attenuation with distance.For technical management of the fields with indoor distribution substations both public and occupational exposure is possible. There is a number of possible mitigation methods. For existing structures the best mitigation method is usually a combination of several methods. Generally, the practical mitigation is forced to make a compromise for theoretic mitigation methods because of the limited space available. For new indoor distribution substations the structure can be chosen from recognized good construction methods.Technical management of the fields with arc furnaces is highly case-specific. Generally, the occupational exposure is important. The best mitigation method is attenuation with distance, which can be taken into consideration when designing a new arc furnace. For existing structures, the best way to consider magnetic field is to avoid working near the arc furnace in the area, where the magnetic field can exceed exposure guidelines.Based on the studied cases, it can be stated that the technical management chain for the electric system contains specification of the problem, solving of the fields with calculations and measurements, mitigation, operations and analysis of the solutions. The operational part of the technical management chain consists of electric and magnetic field mitigation. The technical management chain can be used for solving similar problems in the future.
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