The Influence Of Oil-immersed Transformer Insulation Paper On Winding Temperature

Due to economic development and the needs of life,more and more large-capacity transformers are connected to the grid.Among them,oil-immersed self-cooled transformers account for the largest proportion.The temperature distribution of the winding is affected by many factors due to the complex internal environment.The winding insulation paper in the oil-immersed transformer is an important part of the insulation system and is a kind of thermal poor conductor,which evenly wraps the winding and is immersed in transformer oil for a long time,which forms a blocking effect on the heat transfer between the winding and transformer oil.Insulated paper wrap winding is not conducive to the heat dissipation of the winding,and the winding temperature is higher than that without the insulating paper,and the insulating paper is often ignored as part of the heat transfer.In order to analyze the influence of winding on the temperature rise of the winding when insulating paper is wrapped,his paper takes a 10,000KVA/35 KV oil-immersed transformer produced by a company in Yunnan as the research object,and uses the fluid mechanics simulation software ANSYS CFX to build a natural oil circulation transformer according to the actual size,establish a coupled heat transfer model of the temperature field and flow field of the winding area of the natural oil circulation transformer,and analyze the hot spot temperature and temperature distribution of the winding when the insulation paper is wrapped.The temperature measurement experiment of the winding temperature of this type of transformer is carried out by using the fiber grating temperature sensor,and the obtained result is compared with the simulation result.The experiment of directly measuring the winding temperature by the fiber temperature sensor verifies the validity of the simulation model.In order to study the temperature change of the winding when the insulation paper with different thicknesses of insulation paper,different layers of insulation paper is outsourced,this paper uses the verified physical model to perform simulation analysis based on the thermal resistance of the insulation paper in different situations,and obtains the relationship between the insulation paper and the winding temperature in various cases.In engineering applications,according to the relationship between the insulation paper and the winding temperature,it canaccurately know the hot spot temperature of the winding,protect the internal insulation system,and extend the service life.The main content of this article is as follows:(1)Based on Fourier’s law of heat conduction,the thermal resistance characteristics of insulating paper with different thickness and different layers are obtained by designing a steady-state dual-heat flowmeter experiment.According to the actual structure size of the transformer,the three-dimensional physical model is established using the finite element software ANSYS CFX simultaneous solid domain winding and fluid domain transformer oil to calculate the heat transfer,and the temperature distribution of the winding when the actual thickness of the insulation paper is wrapped around the winding.(2)The temperature of the winding is collected in real time by arranging multiple fiber Bragg grating temperature sensors in different positions in the transformer.In order to verify that the established physical model is superior to the modeling of ignoring insulation paper,it provide a theoretical basis and an accurate physical model for studying the relationship between the insulation paper and the temperature and temperature distribution of the hot spot of the winding in various situations,it is necessary to analyze the measured experimental data and the simulation results simultaneously.(3)Based on the three-dimensional coupling model,and based on the results obtained from the thermal resistance experiments of the insulation paper,perform simulation calculations on the insulation paper outer windings of different thicknesses and different layers to obtain the relationship between the insulation paper and the winding temperature.The research method used in this article is to establish a physical model according to the actual size of the transformer,which is also applicable to other types of transformers,which provides a reference for accurately knowing the hot spot temperature of the winding.