Fating Yuan

The long-term operation of oil-immersed transformers causes rapid internal temperature rise, which may lead to accidents such as transformer burning, which has a certain impact on the safe and reliable operation of the power grid. This paper uses finite element simulation to establish a 3-D circuit-magnetic field model based on transformer parameters, accurately calculating core and winding losses. The calculated loss is loaded into the simulation model of the flow temperature field, and the distribution characteristics of the temperature field and flow field of the transformer core and winding are obtained accurately by analyzing the heat transfer mode of the transformer. Through central composite design and range analysis, optimal winding geometry parameters minimizing hot spot temperature are determined. In order to further reduce the temperature rise of the transformer, the principle of enhanced heat dissipation is used, and the cooling module is attached to the radiator of the transformer model, with its shape, position, installation method, and quantity optimized via heat-flow coupling calculations to obtain the optimal scheme to minimize the hot spot temperature of the transformer. The results show that the hot spot temperature of the oil-immersed transformer can be reduced from 78.1? to 60.7?, and the hot spot temperature can be reduced by 22.3%. The aforementioned research provides a new idea and reference for oil immersed transformer to reduce temperature rise and improve heat dissipation performance.

The optimization method of winding structure parameters of oil-immersed transformer is proposed to reduce the hot spot temperature of transformer and the metal conductor consumption based on the coupling calculation method of electromagnetic-fluid-thermal. Firstly, a 3-D simulation model is established by using finite element software, and the distribution of the thermal field and the fluid field around the transformer as well as the fluid field and thermal field of the low-voltage winding are obtained. Considering the calculation efficiency and accuracy, a 2-D model of transformer low-voltage winding is established, and the thermal field and flow field distribution of the two models are compared and analyzed. The temperature error was less than 5.98?, which verified the accuracy of the equivalent model. On this basis, combined with Latin hypercube experiment design and thermal field simulation method, the response surface model of winding hot spot temperature and structural parameters is established. Taking the hot spot temperature of low voltage winding and the amount of metal conductor as optimization objectives, the optimal solution set of Pareto is obtained by using NSGS-? optimization algorithm, and two kinds of optimal design results are obtained on the Pareto front surface. The results show that the hot spot temperature is reduced by 4.16% and the metal conductor consumption is reduced by 13.79% in Scheme 1 and the hot spot temperature is reduced by 0.51% and the metal conductor consumption is reduced by 28.46% in Scheme 2. The research results have important guiding significance for the optimization of oil-immersed transformer.

The hot spot temperature is an important factor affecting the operation state and insulation life of oil-immersed transformer. It is of great value to carry out multi-physical field coupling simulation research on magnetic-fluid-thermal field of oil-immersed transformer and accurately calculate and predict the hot spot temperature of transformer for transformer service life evaluation. In this paper, the oil immersed transformer is taken as the research object, and five characteristic parameters of the hysteresis model are obtained by using PSO algorithm according to the experimental magnetic characteristics data of the core material and the classical Jiles-Atherton (J-A) hysteresis model, A 3-D simulation model of magnetic-fluid-thermal field is established based on the electrical and structural parameters of the oil-immersed transformer. Combined with the magnetic characteristics of the core material, the thermal field and the surrounding fluid distribution of the transformer core and winding are obtained by two-way coupling method. On this basis, in order to accurately reflect the correlation between the hot spot temperature of the transformer winding and the temperature of the oil tank wall, the selection position of the characteristic temperature point of the transformer tank wall is determined by streamline analysis method, and the hot spot temperature of the oil-immersed transformer is retrieved by support vector machine method. The results show that the prediction accuracy of the hot spot temperature reaches 0.998, and the inversion method has a high enough accuracy. It provides theoretical basis and technical support for real-time monitoring of hot spot temperature in oil-immersed transformer windings.

The hot spot temperature of oil-immersed transformer winding is an important factor affecting the aging of material insulation. In this paper, a magnetic field simulation model is established based on the electrical and structural parameters of the oil-immersed transformer, and the loss distribution characteristics of each wall of the transformer core, winding and fuel tank are accurately calculated by using the finite element simulation software. The simulation model of transformer fluid-thermal field is established, the simulation results of transformer thermal field are obtained, and the temperature distribution of oil-immersed transformer core and winding and the flow velocity around it are obtained. According to the simulation results of thermal field, the characteristic temperature measuring points with strong correlation between tank wall and winding temperature were determined. The inversion models of tank wall and winding hot spot temperature were established by using the support vector regression and back propagation neural network algorithm, respectively by central composite design method. The results show that the correlation coefficient of support vector regression algorithm in predicting winding hot spot temperature reaches 0.98, and the relative error between the model predicted value and the real value is less than 8%, which is more accurate than back propagation neural network. The aforementioned research provides the theoretical basis and technical support for real-time monitoring of oil-immersed transformer winding hot spot temperature.

In this paper, according to the design parameters of oil-immersed iron core reactor, the thermal network model of windings is established by the thermo-electric analogy method, and the temperature distribution of the windings can be obtained. Meanwhile, a fluid-thermal coupled finite element model is established, the temperature and fluid velocity distribution are extracted, and the simulation results show that the error coefficient of temperature is less than 3% compared with the thermal network model, so the correctness of thermal network model has been verified. Taking the metal conductor usage and loss of windings as the optimization objects, the optimization method based on the particle swarm algorithm and thermal network model is proposed, and the Pareto optimal solutions between the metal conductor usage and loss of windings are given. The optimization results show that the metal conductor usage is reduced by 23.05%, and the loss is reduced by 20.25% compared with the initial design parameters, and the maximum temperature of winding does not exceed the expected value. Thus, the objects of low metal conductor usage and loss of windings are conflicted and cannot be optimized simultaneously; the optimization method has an important guiding significance for the design of oil-immersed iron core.

In this paper, the basic structure and design parameters of an oil-immersed air core coupling reactor were given according to the interruption requirement of the 160 kV mechanical direct current circuit breaker, and a field-circuit coupled finite element model was established based on the ANSOFT simulation platform. The prototype test results verified the correctness of the simulation calculation method. The coupling reactor design was optimized to minimize the total volume, taking equal height and heat flux design parameters as the optimization object, and the influence of the insulation distance between the oil tank and encapsulations on the secondary current of the coupling reactor were analyzed. Meanwhile, a combined optimization method about the reactor body and oil tank was proposed, and the optimization contour surface was plotted, which described the relationship between the total volume of the coupling reactor and structure parameters of the reactor body and oil tank. According to the optimization design results, the total volume was only 89% compared with the initial design parameters, and the correctness was verified by the simulation results.

In this paper, in accordance with the breaker requirements of a parallel-type circuit breaker based on a high-coupling split reactor, the structure of a coupling reactor is proposed, and the influences of the inner radius, encapsulation height, air ducts width and encapsulation number of the reactor on coupling factor are analyzed. The reactor design is optimized to minimize metal conductor usage, and the initial design parameters of the coupling reactor are selected based on equal height and heat flux of the coaxial encapsulations. Meanwhile, combined thermal and electromagnetic optimization method and heat load optimization are adopted considering a single-arm limiting current and two-arm flow current working conditions. The optimization results show that the metal conductor usage of the coupling reactor is only 63% compared to a design based on the initial design parameters, and the correctness of the optimization is verified by simulation results.

In this paper, taking the minimum metal conductor usage of an air core reactor as optimization goal, the influence of air ducts width and encapsulation number on thermal efficiency and electromagnetic efficiency are analyzed. Combined with the equation constraint conditions for maximum temperature rise conservation, inductance conservation and structure function of reactor considering the change of air ducts width and encapsulation number, the thermal and electromagnetic combined optimization curves are formed, and design results are achieved based on the initial design parameters. Meanwhile, the temperature field simulation model of the reactor is established and the results verify the correctness of the optimization method. According to the design results, the proportionality factor of metal conductor usage is only 0.61 compared with the initial design parameters of the reactor, which shows that the proposed comprehensive optimization method can significantly reduce conductor usage, improving the metal conductor utilization ratio.