Modelling of Thin Conductive Screens for ELF Magnetic Field Attenuation by Finite Element and Integral Methods

Mitigation of ELF (Extremely Low Frequency) magnetic fields is often performed by means of highly conductive laminar shields. Usually 2D codes are used for ELF shield design purposes in order to reduce computing requirements. In this paper it is shown that a 3D integral method can be used instead, providing a much higher accuracy with similar computational costs. It consists of an original procedure based on the Cell Method able to model properly the actual geometry of the arrangement. Comparisons between the two methods are applied in some typical configurations. The discrepancy between 2D and 3D approaches is analyzed as a function of shield shape (flat and U-shaped) and dimensions (thickness, width and length). The 3D integral procedure is used then for assessing the shield performance of flat and U configurations. Eventually, the same procedure is successfully applied to analyze a real case shield installed in a 20 kV/400 V substation.