油浸式变压器温度场分析与油流对内部温升影响因素研究
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摘要
变压器是电力系统的关键设备,油浸式变压器广泛使用在各个等级的电网中,变压器的可靠安全是电网稳定运行的保证。由于变压器是一次设备,运行环境比较恶劣,特别是由于变压器损耗产生的热严重影响变压器内部绝缘部件的寿命,在大型变压器内部表现的更为严重。在强油循环变压器中,采用油泵的强油循环冷却变压器,在油流速过快的情况下,产生油流带电现象,不利于变压器的安全运行；油流速过慢,又不利于散热。因此,探究流场与温度分布的关系,对控制变压器内部油流速,降低变压器温升,提高其绝缘寿命具有重要意义。对于自然油循环变压器,油流是由温度导致密度变化产生的受迫流动,油流速度低,散热效果差,影响温度的因素较多也较复杂,研究结构对油流和温度分布的影响以及环境、负载等外界因素对温升的影响,对改善变压器的散热结构和运行环境有重要价值。
通过分析变压器内部热源、强油循环和自然油循环变压器散热的方式和途径,建立了变压器内部热传导数值计算微分方程,提出了固液交界面上的对流换热系数求解方法。
建立强油循环变压器二维K—ε两方程湍流流固油流温度场耦合传热数值模型。运用有限体积法计算了温度场和油流场的分布,分析了油流场与温度场分布之间的关系,研究了入口流量与变压器内部各油道流速的关系,探讨了流速与温升的关系,分析了入口油流温度和负载系数与变压器内部温升的关系。
建立自然油循环变压器二维封闭区域内受迫的层流流固油流温度场耦合传热数值模型。研究了三种不同结构(无绝缘结构、有绝缘结构、有绝缘和导向结构)的模型,分析了受迫油流与温度场之间的关系,比较了三种结构对温升与油流的影响,探讨了负载系数、散热器高度、径向油道高度、环境温度对变压器内部温升的影响规律。
Oil-immersed Transformer, the key equipment of the power system, is widely used in various levels of power grid. The reliable safety of the transformer is the guarantee of stable operation of the grid Because the transformer is primary equipment, running environment is bad, especially the heat by loss generated in the transformer seriously affect the service life of the insulation of internal components in the transformer, and even more serious in the performance of large transformer. Winding and iron core inside the forced oil-cycling transformer are cooled by oil flowing driven by pump, but velocity of oil flow is too fast, producing oil flow electrification between oil and insulator, which is not conducive to the safe operation of transformer. Thus, researching on the relation between flow field and temperature distribution is necessary which can be not only effectively controlling internal oil flow rate of transformer, but also better cooling the internal components. The oil flowing in natural oil-cooled transformer is caused by the density change due to temperature, so the velocity of flow is low, producing poor cooling effect. The factors influencing the cooling temperature is complex, studying the effect of structure, external factors such as environment and load on the flow and cooling temperature distribution, plays an important value on improvement of cooling and operation environment.
By analyzing the transformer internal heat source, differential equation of numerical calculation of both of forced oil-cooled and natural oil-cooled transformer is established. The solid heat conduction and the convective heat transfer equation on the surface of the solid-liquid interface is given. The method of calculating the convective heat transfer coefficient, and the oil flow within the numerical equations of mass, momentum and energy is established.
Two equation of turbulence numerical model of fluid-solid heat coupling in forced oil circulating transformer is established. Temperature field and flow field is calculated by the finite volume, and the relationship between the flow field and temperature field distribution is studied. Further research is done on the inlet flow and the transformer inside the oil duct flow relations, discussing the relationship between the velocity and temperature rise, in-depth analysis of the inlet flow temperature and internal temperature rise of transformer and load coefficient.
2-D numerical model of the laminar flow of fluid-solid coupling flow temperature field in nature oil-cooled transformer is created. Three different structure of the model is studied, and the forced flow and temperature field are analyzed. the relationship between oil flow and temperature distribution is given. The comparison of the three kinds of structure (no insulation structure, insulating structure, insulating structure and oil-guide plate) is made on the effect of the temperature rise and oil flow. The factors affecting temperature such as load, the height of the radiator, the radial oil duct height, environmental temperature on the internal temperature of transformer are also studied.
通过分析变压器内部热源、强油循环和自然油循环变压器散热的方式和途径,建立了变压器内部热传导数值计算微分方程,提出了固液交界面上的对流换热系数求解方法。
建立强油循环变压器二维K—ε两方程湍流流固油流温度场耦合传热数值模型。运用有限体积法计算了温度场和油流场的分布,分析了油流场与温度场分布之间的关系,研究了入口流量与变压器内部各油道流速的关系,探讨了流速与温升的关系,分析了入口油流温度和负载系数与变压器内部温升的关系。
建立自然油循环变压器二维封闭区域内受迫的层流流固油流温度场耦合传热数值模型。研究了三种不同结构(无绝缘结构、有绝缘结构、有绝缘和导向结构)的模型,分析了受迫油流与温度场之间的关系,比较了三种结构对温升与油流的影响,探讨了负载系数、散热器高度、径向油道高度、环境温度对变压器内部温升的影响规律。
Oil-immersed Transformer, the key equipment of the power system, is widely used in various levels of power grid. The reliable safety of the transformer is the guarantee of stable operation of the grid Because the transformer is primary equipment, running environment is bad, especially the heat by loss generated in the transformer seriously affect the service life of the insulation of internal components in the transformer, and even more serious in the performance of large transformer. Winding and iron core inside the forced oil-cycling transformer are cooled by oil flowing driven by pump, but velocity of oil flow is too fast, producing oil flow electrification between oil and insulator, which is not conducive to the safe operation of transformer. Thus, researching on the relation between flow field and temperature distribution is necessary which can be not only effectively controlling internal oil flow rate of transformer, but also better cooling the internal components. The oil flowing in natural oil-cooled transformer is caused by the density change due to temperature, so the velocity of flow is low, producing poor cooling effect. The factors influencing the cooling temperature is complex, studying the effect of structure, external factors such as environment and load on the flow and cooling temperature distribution, plays an important value on improvement of cooling and operation environment.
By analyzing the transformer internal heat source, differential equation of numerical calculation of both of forced oil-cooled and natural oil-cooled transformer is established. The solid heat conduction and the convective heat transfer equation on the surface of the solid-liquid interface is given. The method of calculating the convective heat transfer coefficient, and the oil flow within the numerical equations of mass, momentum and energy is established.
Two equation of turbulence numerical model of fluid-solid heat coupling in forced oil circulating transformer is established. Temperature field and flow field is calculated by the finite volume, and the relationship between the flow field and temperature field distribution is studied. Further research is done on the inlet flow and the transformer inside the oil duct flow relations, discussing the relationship between the velocity and temperature rise, in-depth analysis of the inlet flow temperature and internal temperature rise of transformer and load coefficient.
2-D numerical model of the laminar flow of fluid-solid coupling flow temperature field in nature oil-cooled transformer is created. Three different structure of the model is studied, and the forced flow and temperature field are analyzed. the relationship between oil flow and temperature distribution is given. The comparison of the three kinds of structure (no insulation structure, insulating structure, insulating structure and oil-guide plate) is made on the effect of the temperature rise and oil flow. The factors affecting temperature such as load, the height of the radiator, the radial oil duct height, environmental temperature on the internal temperature of transformer are also studied.
引文
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[3]谢文景.变压器绝缘老化分析及其寿命管理[J].广东电力,2001(4)：15-17.
[4]王晓莺.变压器故障与监测[M].北京：机械工业出版社,2004.
[5]杨启平等.变压器绝缘老化的诊断与寿命评估[J].变压器,2004(2)：13-17.
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[10]杨智博.变压器油中局部放电下的油流带电分析[J].变压器,2009,46(3)：47-50.
[11]陈国元.强迫油循环变压器油流带电的危害及其抑制[J].华北电力技术,1992(8)：30-35.
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[13]张维力.电力变压器绕组温度光纤监测技术[J].华北电力技术,1995,11(2)：44-47.
[14]牟长江.用光纤技术直接测量变压器绕组热点温度[J].变压器,1995,32(11)：2-5.
[15]赵涛.基于光纤光栅温度传感的变压器内部温度监测原理及方法研究[D].硕士学位论文,重庆大学,2008.
[16]Swift G, Molinski T. A fundamental approach to trans-former thermal modeling-part I: theory and equivalent circuit[J]. IEEE Trans Power Deliv,2001,16:171-175.
[17]Ryder S. A simple method for calculating winding temper-ature gradient in power transformers[J]. IEEE Trans Power Deliv,2002,17:977-982.
[18]Ryder S, Vaughan IJ. A simple method for calculating core temperature rise in power transformers[J]. IEEE Trans Power Deliv.2004,19:637-642.
[19]Radakovic Z, Maksimovic S. Non-stationary thermal model of indoor transformer stations[J]. Electr Eng.2003,84:109-117.
[20]Elleuch M, Poloujadoff M. A contribution to the modeling of three phase transformers using reluctances[J]. IEEE Trans Magn.1996,32:335-343.
[21]周利军.牵引变压器温升与微水扩散特性的研究及其状态预测[D].博士学位论文,西南交通大学,2007.
[22]陈伟根,苏小平,周渠等.基于顶层油温的变压器绕组热点温度计算改进模型[J].重庆大学学报,2012,35(5)：69～75.
[23]江淘莎,李剑,陈伟根.基于底层油温的油浸式变压器绕组热点温度计算热路模型的研究[J].高电压技术,2009,37(7)：1635～1640.
[24]李剑,刘兴鹏,王有元等.以箱壁温度为判据的油浸式变压器绕组热点温度计算模型及试验分析[J].高电压技术,2011,37(10)：2344-2344.
[25]陈伟根,苏小平,周渠等.基于顶层油温的变压器绕组热点温度计算改进模型[J]。重庆大学学报,2012,35(5)：69～75.
[26]陈伟根,奚红娟,苏小平等.广义回归神经网络在变压器绕组热点温度预测中的应用[J].高电压技术,2012,38(1)：16～21.
[27]滕黎,陈伟根,孙才新.油浸式电力变压器动态热路改进模型[J].电网技术,2012,36(4)：236～241.
[28]崔昊杨,唐忠,朱捷等.电力变压器铁心温度场分布的数值模拟及分析[J].上海电力学院学报,2010,26(5)：425-428.
[29]熊兰,赵艳龙,杨子康等.树脂浇注干式变压器温升分析与计算[J].高电压技术,2013,39(2)：265～271.
[30]王秀春.大型强迫导向油循环冷却变压器系统的流动、传热分析及线圈温度场数值计算[D].硕士学位论文,北京钢铁学院,1991.
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[32]贾子瑜,姚日琪,王秀莲等.强油导向冷却电力变压器的油流工程计算方法[J].变压器,1998,35(2)：34～37.
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