Entity

Time filter

Source Type


Liao R.-J.,Chongqing University | Sun H.-G.,ABB | Gong J.,Zhejiang Electrical Power Corporation | Li W.,Bishan Power Supply Bureau of Chongqing Electrical Power Corporation | And 2 more authors.
Gaodianya Jishu/High Voltage Engineering | Year: 2011

Using #25 transformer oil and ordinary kraft paper as raw materials, we simulated the actual transformer production process, in which the initial moisture contents of the oil-paper samples were set to be 1%, 3%, and 5%, and were aged at 90°C, 110°C, and 130°C. Moreover, we analyzed the polymerization degree of insulation paper in ageing process and cellulose degradation kinetic model in terms of DP. The main conclusions can be drawn as follows: the higher temperature and the more moisture contents are, the faster the degree of polymerization will decline, and more rapidly the oil-paper insulation will age. The insulation ageing rate is not constant but decreases with ageing time. The cellulose degradation kinetic model in terms of the DP loss accumulation is able to explain the real experimental data of cellulose ageing in mineral oil under different temperature and moisture contents. The apparent activation energy for kraft paper ageing in mineral oil is Ea=(101±15) kJ/mol. The oil-paper insulation life prediction model is thus established based on time-temperature superposition theory and DP loss accumulation kinetic model. Source


Liao R.-J.,Chongqing University | Li W.,Chongqing University | Li W.,Bishan Power Supply Bureau of Chongqing Electrical Power Corporation | Yang L.-J.,Chongqing University | And 3 more authors.
Gaodianya Jishu/High Voltage Engineering | Year: 2011

In order to understand the relationship between thermal aging level of oil-paper insulation and its space charge properties, accelerated thermal aging tests were conducted on samples composed of #25 mineral oil and ordinary Kraft paper. The space charge properties of aged samples under DC voltage (20 kV/mm) were studied by using the pulsed electro-acoustic (PEA) method, and the impact of aging on the space charge evolution as well as the electric field distortion was discussed. The results show that during thermal aging, the deeper the trap emerges, the more space charge accumulates and the internal field distortion is enlarged as well under DC voltage, moreover, the duration of charge dissipation and internal field distortion become longer respectively. Furthermore, an exponential relationship between the total charge and decay time was obtained and the decay time constant τ was proposed, which could help realize the evaluation of charge dissipation ability in different samples. The results provide a basis for evaluation the electrical properties of oil-paper insulation system under different thermal aging conditions. Source


Liao R.-J.,Chongqing University | Li W.,Chongqing University | Li W.,Bishan Power Supply Bureau of Chongqing Electrical Power Corporation | Yang L.-J.,Chongqing University | And 3 more authors.
Gaodianya Jishu/High Voltage Engineering | Year: 2011

In order to enhance the service life of transformers and its insulation level, synthetic fiber insulation paper has been widely used in the dielectric insulation engineering because of its excellent dielectric, mechanical and thermal stability, moisture resistance and other properties. Injection, accumulation and dissipation characteristics of space charge were studied by pulsed electro-acoustic (PEA) method in samples of NOMEX synthetic fiber paper under DC field, and were compared with those of the traditional plant cellulose insulation paper with dielectric properties. The results reveal that NOMEX paper has a lower space charge accumulation threshold field and it is easy to inject and accumulate space charge, and it is hard to dissipate after short circuit under DC field. The space charge characteristics of NOMEX synthetic fiber paper are closely associated with its surface topography, morphology and dielectric properties. In a sense, these characteristics contribute to restrain the transportation of space charge in the dielectric. Source


Li W.,Bishan Power Supply Bureau of Chongqing Electrical Power Corporation | Liao R.,Chongqing University | Yuan X.,Bishan Power Supply Bureau of Chongqing Electrical Power Corporation | Huang J.,Bishan Power Supply Bureau of Chongqing Electrical Power Corporation | And 2 more authors.
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2012

In order to understand the influence of thermal aging on the evolution and mechanism of space charge formation of cellulose insulation papers used in transformers, the volt-on and decay charge density distribution for insulation papers with different aging conditions were measured by the pulsed electro-acoustic (PEA) method under different electrical field strength (30, 15, 5 kV/mm). The relationship between the thermal aging level and the evolution of space charge in insulation papers was analyzed. Results show that the amount and the injection rate of charge in insulation papers increase in a direct proportion with the voltage level applied. Thermal aging reduces the space charge injection threshold voltage of insulation papers. And the charge injection rate, charge mobility and charge combination in the insulation paper were also depressed. The trap distribution density and trap depth in insulation papers increase with the thermal aging degree, which leads to the increasing amount of the residual space charge and the reduced decay rate of the residual space charge in insulation papers. The theoretical support was provided to understand the influence of thermal aging on the space charge formation and dissipation mechanism of insulation papers. © 2012 Chinese Society for Electrical Engineering. Source

Discover hidden collaborations