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Chen Q.,Harbin University of Science and Technology | Chi M.,Harbin University of Science and Technology | Gao Y.,Harbin University of Science and Technology | Wei X.,Harbin University of Science and Technology | And 2 more authors.
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2013

In order to study the breakdown characteristics of oil-pressboard insulation under compound electric field, the typical oil-pressboard insulating structure was taken as the study object. The breakdown characteristic of typical oil-pressboard insulation was obtained under compound electric field via breakdown tests at first. Then the electric fields in oil and oil-impregnated pressboard were simulated according to the equivalent circuit. The breakdown characteristic tests of oil and oil-impregnated pressboard were carried out separately under compound electric field. On the basis of the electric field mathematical expressions of the oil and oil-impregnated pressboard, the relationship between the electric field E and AC content (was got, and the electric field distribution in oil and oil-impregnated pressboard was compared with their breakdown strengths. And then the breakdown voltage mathematical expressions with AC content were concluded. The results showed that the main reason why the breakdown voltage of oil-pressboard insulating structure rises before and falls later is that the electric fields in the two materials vary with the AC content and there is difference in breakdown characteristics between two materials. © 2013 Chin. Soc. for Elec. Eng.


Duan X.-M.,Harbin Institute of Technology | Jia D.-C.,Harbin Institute of Technology | Yang Y.,Harbin Military Representative Office of the Second Artillery | Meng Q.-C.,Harbin Institute of Technology | And 4 more authors.
Cailiao Kexue yu Gongyi/Material Science and Technology | Year: 2011

ZrO 2p(3Y)/BN-SiO 2 ceramics composite with different ZrO 2 content were hot pressed using h-BN, amorphous silica, and ZrO 2(3Y) powders as starting materials. With the increase of ZrO 2 contents, the relative density, flexural strength, elastic modulus increase monotonously. When the ZrO 2 content reach to 20vol.%, the maximum values are 96.6%, 320.6 MPa, 92.3 GPa, respectively. Fracture toughness increase firstly and then fall as the temperature rises, it reach to 3.6 MPam 1/2 with the 15vol.% ZrO 2 content. Flexural strength of the composites declined after thermal shocking. The residual flexural strengths were 74.9% and 43.8% of its original value for thermal shock temperature of 700°C and 1100°C which showed that the ceramics composite had good thermal shock properties.


Yang Z.,Harbin Institute of Technology | Jia D.,Harbin Institute of Technology | Chu L.,Harbin Military Representative Office of the Second Artillery | Duan X.,Harbin Institute of Technology | And 3 more authors.
Kuei Suan Jen Hsueh Pao/Journal of the Chinese Ceramic Society | Year: 2010

Nano TiN-Al2O3 composite ceramics were prepared by hot-pressing using nano Al2O3 and TiN as raw materials and SiO2 as sintering additive. The flexural strength of the as-prepared ceramics is up to 565.8 MPa and the fracture toughness is between 4 and 6 MPa · m1/2. The cubic TiN grains are homogenously distributed in Al2O3 matrix in the composite ceramics. Most of TiN particles lay in the grain boundaries of Al2O3. When the volume fraction of TiN was 5%, the electrical resistivity of TiN-Al2O3 composite ceramics is between 1012 to 104 Ω · cm. The highest on-load voltage of the ceramics could reach 0.75 kV/mm.


Chen Q.-G.,Harbin University of Science and Technology | Chi M.-H.,Harbin University of Science and Technology | Wang G.,Harbin University of Science and Technology | Gao Y.,Harbin University of Science and Technology | And 2 more authors.
Dianji yu Kongzhi Xuebao/Electric Machines and Control | Year: 2013

In order to study the moisture influence on the electric field distribution of oil-pressboard insulation in converter transformer, the equivalent physical model and circuit model were established according to the typical oil-pressboard compound insulation structure, and the mathematical expression for electric field distribution calculation under compound electric field was obtained. According to the measured results of resistivity and relative permittivity of transformer oil and oil impregnated pressboard with different moisture under different temperature, the relationship between electric field distribution and moisture & AC content was obtained for typical oil-pressboard insulation under compound voltage. The results show that the moisture has great influence on the electric field distribution of oil-pressboard insulation under compound voltage. With moisture increasing, the electric field strength in oil will be enhanced; meanwhile electric field strength in oil-impregnated pressboard will be reduced, when moisture in oil and pressboard reaches equilibrium state. When the oil-pressboard insulation moisture increases, the electric field strength varies accelerated. The moisture has more influence on oil-pressboard resistivity than that on permittivity, which results in the great moisture influence on the electric field distribution in oil-pressboard insulation under compound voltage with the higher DC content.

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