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ABSTRACT: Nano-composite technology makes it possible to improve dielectric properties, such as resistivity, breakdown strength and so on, under high DC stress. However, the mechanism of the improvement in MgO nano-composite LDPE (LDPE/MgO) has not been clear, yet. We attempted to clarify the mechanism of the improvement on the electrical properties focused on the space charge formation. To investigate the influence of MgO nano-filler on space charge profiles, we measured the space charge distributions using PEA system under DC electric field of 50 to 250 kV/mm. In the case of LDPE without nano-filler, a positive packet-like charge injection with peak charge density of more than several hundred C/m<sup>3</sup> were measured under more than 150 kV/mm. In the case of LDPE/MgO with MgO content of 0.2 phr, an oscillating behavior of packet-like charge was observed when the DC electric field of more than 200 kV/mm was applied to it. On the other hand, in the case of LDPE/MgO with MgO content of more than 0.5 phr, there is no remarkable charge injection. It is thought that space charge behavior is drastically changed by adding only more than 0.5 phr of MgO to LDPE. The nano-composite including more than 0.5 phr shows a superior property to prevent the injection of space charge into bulk
Properties and applications of Dielectric Materials, 2006. 8th International Conference on; 07/2006
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ABSTRACT: In this paper, the outline of the development history of HVDC cable with nanocomposite material is introduced. Nano-sized MgO-filler added into XLPE, which had been developed for HVDC cable insulation, was not investigated from the view point of nanocomposite material until 2001. Since then, nano-scale observation of the dispersion state of nano-sized MgO-filler in HVDC cable insulation has been carried out. It has been found that the dc material, which had been developed for 500 kV dc cable, is XLPE/MgO nanocomposite material in which nano-sized MgO homogeneously dispersed in nano-scale
Properties and applications of Dielectric Materials, 2006. 8th International Conference on; 07/2006
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ABSTRACT: Polymer nanocomposite has been attracting much attention as a new insulating material, since homogeneous dispersion of only few nm-sized inorganic fillers can improve various properties significantly. In the present article, we report measurement results of permittivity, conduction current, and space charge distribution profiles observed in low-density polyethylene/MgO nanocomposites with various filler contents. The permittivity shows the lowest value at 1-phr addition of fillers and then increases monotonically with an increase in the filler content. The volume resistivity measured under a dc electric field becomes highest at 5 phr in the temperature range between 278 and 363 K. There is a possibility that molecular motions, which help electronic or ionic charge carriers escape from traps by hopping, are restricted by the addition of a proper quantity of nano-fillers. In all the samples, homocharge is found to be formed before the anode
Properties and applications of Dielectric Materials, 2006. 8th International Conference on; 07/2006
