Research On Temperature Distribution Characteristics Of Oil-immersed Transformer Windings Based On Thermoelectric Analogy

Oil-immersed transformer is one of the most important equipments in all power grids.Its safe and reliable operation is the basic element of safe operation of the power grid.Due to the long-term operation of the oil-immersed transformer,its winding and iron core will generate a large amount of heat,which will cause the temperature of transformer winding to rise,which will affect the chemical change of the insulating paper on the outer layer of the winding,and will also affect the load of the transformer,so the temperature distribution of transformer winding needs to be further studied.On the basis of reviewing a large number of literatures,the paper studies the temperature distribution of the winding by establishing the simulation of the thermal circuit model and designing a transformer temperature rise platform.The main work of this paper is:1)Analyzing the causes of internal oil flow in oil-immersed transformers and analyzing the load loss and no-load loss of the transformer.Introducing several cooling methods and thermoelectricity analogy theory of transformers and the transformer heat path model firstly established based on thermoelectricity analogy theory.The viewpoint that the hot spot temperature of the transformer winding is not the average winding temperature is proposed.Based on the thermoelectricity analogy theory,the distributed parameter thermal circuit model between the transformer winding and the oil is established.When setting the model parameters,linearly fitting the temperature of the upper,middle,and lower positions in the oil tank obtained by the transformer temperature rise experiment,and using the multisim software to simulate the model,the simulation results are obtained,namely 1.3 times the rated power and 1 times the rated power at the highest temperature point of the winding and the winding height.2)Analyzing the formation of the horizontal oil gallery between the transformer winding discs,proposing the concept of simulating the winding room between the discs,and setting up an experimental platform based on the steady-state heat flow method.The experimentally measured data was used to calculate the thermalresistance per unit area between the transformer winding and discs,and compared with the calculated thermal resistance between the winding using traditional empirical formulas.The experimental results were analyzed,and then brought into the distributed parameter thermal path model established in Chapter 2,the simulation results are obtained.3)In order to verify the correctness of the distributed parameter thermal path model,a temperature rise experimental platform for transformer temperature measurement using a fiber Bragg grating temperature sensor was built.Analyzing the measurement results,it is found that under different loads,the hot spot temperature of the winding is not at the same position,which verifies that the hot spot temperature of the winding is not the average temperature of the winding.Comparing the temperature obtained by the experiment with the simulation results,it verifies the correctness of the distributed parameter thermal model and the greater accuracy of the experimental calculation of the thermal resistance between the discs.