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In this paper a detailed description of different passive shields for Extremely Low Frequency (ELF) applications is presented. The first part of the paper analyzes ferromagnetic and conductive materials by means of simulations and measurements. This step is mainly devoted to the identification of physical characteristics such as the relative permeability of the analyzed ferromagnetic materials. All the simulations are performed with a standard Finite Element (FE) code assuming linear behavior of the tested materials. The results are then used in the design of many shielding configurations and, finally, three different multilayer shield compositions are tested and presented. The second part of this paper outlines guidelines to assure a good shielding efficiency in the actual installation of a multilayer shield. The orientation of the shield as well as the possible decay of the shielding performance due to the discontinuity among the different slabs is investigated by means of experimental measurements. It is observed that the conductive part of the multilayer shield has to be faced to the source to have better performance. Moreover, it is important to assure the electrical conduction between the separate slabs. In this paper the conduction among different plates is conveniently obtained connecting them by straight bars of aluminum. In the third part of the paper the multilayer shield is tested under actual working conditions. A MV/LV substation was reproduced in the laboratory using a 630 kVA transformer working at its rated power. Several configurations were tested and the most significant results are presented. It is highlighted that, if the proper layout is not employed, the performance of the actual shield can be very different from the one of the material. [ABSTRACT FROM AUTHOR]

In situ polymerization of aniline was carried out of superparamagnetic (Fe3O4) nanoparticles to synthesize the middle molecular weight HCl-doped polyaniline/polyanitroaniline nanocomposites. The HCl-polyaniline/ polyanitroaniline/Fe3O4 nanocomposites have been synthesized with certain composition of Fe3O4 in the composite. Thus, the synthesized composites have been characterized by infrared spectroscopy and X-ray diffraction. The morphology of these nanocomposites was studied by scanning electron microscopy. Further, the conductivity properties have been investigated in the frequency dependence of conductivity. The presence of polarons and bipolarons is made responsible for frequency dependence of conductivity. Cole—Cole plots indicate clear shift in the distribution of relaxation times as the wt% of Fe3O4 in the polymeric matrix changes. These nanocomposites show almost symmetric semicircles of Cole—Cole plots indicating the Debye-type relaxation in their polarization response. [ABSTRACT FROM PUBLISHER]