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Fu Q.,Harbin Institute of Large Electrical Machinery | Fu Q.,State Key Laboratory of Hydropower Equipment | Fu Q.,National Engineering Research Center Hydropower Equipment | Kong F.,Harbin University of Science and Technology | Chen Q.,Harbin University of Science and Technology
Fuhe Cailiao Xuebao/Acta Materiae Compositae Sinica | Year: 2014

In order to study the capability of the main insulation materials of the ocean energy generators under salt spray and humidity thermal ageing condition, the test for the resin-rich molding (RRM) tong-ma epoxy glass fiber power mica (TEGM) insulation materials was carried out under the simulated ocean climatic condition. The water absorption rate of the resin-rich molding insulation materials was measured under different ageing cycles. The surface morphology change before and after the ageing test was analyzed based on the observed results of the sample through the scanning electron microscope (SEM). The frequency dielectric characteristics of the TEGM insulation materials were measured by the broadband dielectric spectrometer at different ageing cycles and different measuring temperatures. The relationships of the microstructure variety and the macroscopic dielectric property were analyzed by the dielectric polarization theory. The results show that the water absorption rate of the TEGM insulation materials sample appears three stages, namely fast absorption stage, slow absorption stage and saturation absorption stage. The relative dielectric constant and loss factor show the rising tendency with the increasing ageing time, and the frequency domain spectroscopy (FDS) curve can reflect the insulation ageing state directly in the low frequency range. Through the curve fitting of measured data, it can be seen that there are the quadratic equation relationships between the dielectric parameters and the water absorption for the aging insulation materials in the low frequency range. Source


Fu Q.,State Key Laboratory of Hydropower Equipment | Fu Q.,National Engineering Research Center Hydropower Equipment | Fu Q.,Harbin Institute of Large Electrical Machinery | Lu C.,State Key Laboratory of Hydropower Equipment | And 13 more authors.
Proceedings of 2011 International Conference on Electronic and Mechanical Engineering and Information Technology, EMEIT 2011 | Year: 2011

The high voltage capacity is enlarged constantly, which needs good anticorona materials and suitable anticorona structure. When researching and optimizing anticorona structure, it needs to have the knowledge of the development status of anticorona materials for high voltage generators. This paper covers the ways of optimization process of anticorona materials from the following aspects: the choice of raw materials, the performance of SiC powder, the influence of doped materials on anticorona performance. Once-solidification- molding anticorona and painting anticorona are respectively suitable for the resin-rich insulation system and the vacuum pressure impregnation (VPI) resin-less insulation system. The gas permeability of the prefabricated carrier tapes and the stability of the anticorona layer resistances are the important factors to influence on using the once-solidification-molding anticorona structure in VPI resin-less insulation system. The resistance dispersion of the anticorona layers and the SiC content are the important factors to influence on the anticorona effect. The anticorona structure and technology are introduced from the following aspects: additional insulation outside the anticorona layers, the covering lacquer, the influence factors of corona voltage, etc. The optimization calculations of the anticorona structures theoretically summarize the sphere of application for anticorona layer parameters. © 2011 IEEE. Source


Li J.,Harbin Institute of Large Electrical Machinery | Li J.,Xian Jiaotong University | Li J.,National Engineering Research Center Hydropower Equipment | Guo J.,Harbin Institute of Large Electrical Machinery | And 11 more authors.
Materials and Corrosion | Year: 2015

Stress relief annealing treatment is generally applied to keep the dimension stability and tolerance during machining process for casting. However, this process might depress properties of duplex stainless steel (DSS) castings used for sea water circulating pumps in power plants. In this paper, the microstructure and composition analysis of the 25Cr-5.3Ni-2.8Mo-0.15N DSS cast samples affected by stress relief annealing treatment were investigated by SEM and EDS. Meanwhile, uniaxial tensile test, Charpy impact test, and Brinell hardness test were also applied to research the strength, impact toughness, and hardness. Furthermore, the corrosion resistance of 25Cr-5.3Ni-2.8Mo-0.15N cast DSS was also determined by potentiodynamics polarization curves and cyclic voltammety. Brittle sigma phase precipitation has been observed in stress relief annealed samples by SEM and domain elements distribution, especially for samples annealed at 650°C, comparing to the solidification solution treated sample. The strength and hardness of DSS sample stress relief annealed increased significantly, however, the elongation and toughness is depressed comparing to the solidification solution treated samples. Furthermore, the results of electrochemical measurements showed that annealing treatment at 650°C significantly depresses the corrosion resistance of DSS. Therefore, stress relief annealing process of casting samples shall be considered especially due to its brittle transformation and depression of corrosion resistance. © 2013 Wiley-VCH Verlag GmbH & Co. KGaA. Source

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