基于电介质响应法的发电机环氧云母绝缘吸湿特性研究

发布时间：2018-03-21 08:56

本文选题：发电机定子　切入点：环氧云母绝缘　出处：《西南交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：发电机作为电力系统中能源转换的主要电力设备,其定子绝缘系统是发电机的关键部分之一,定子绝缘好坏将直接影响发电机寿命。介电响应法近年来运用于绝缘检测为发电机绝缘状态评估提供了新思路,水分的存在将严重影响发电机定子绝缘检测结果,同时水分又是加速发电机定子绝缘老化的重要因素之一。因此,研究发电机定子绝缘吸湿特性对发电机安全运行和定子绝缘状态准确诊断具有重要意义。本文从微观方面阐释电介质理论,通过数学公式推导出频域介电谱中介质损耗角正切值、复介电常数实部及虚部的表达式。在弛豫模型上引入单弛豫Debye模型和多弛豫Cole-Cole模型,并建立带直流电导的多弛豫Cole-Cole模型以对电介质频域介电谱测试结果进行弛豫过程分析。结果表明:带直流电导的多弛豫Cole-Cole模型比单弛豫Debye模型更能符合多体系的复合电介质介电弛豫过程。通过搭建发电机定子线棒老化平台对发电机定子线棒进行加速老化,通过湿度箱控制定子线棒试样所处环境湿度(M)并搭建频域介电响应(FDS)测试试验平台和传统电阻、电容测试平台对不同湿度下的定子线棒进行测试。根据传统绝缘电阻、电容测试结果得到传统时间常数τ0,并建立带直流电导的双弛豫Cole-Cole模型对发电机定子线棒FDS测试进行拟合分析。结果表明:通过不同温度、湿度状态测得的τ0得到干燥边界,利用干燥边界可判断定子线棒绝缘是否受潮;双弛豫Cole-Cole模型对定子线棒FDS测试结果具有较好的拟合结果,且随着M升高,在10-3～103Hz频率内,界面极化极化强度△εi逐渐增大,而偶极子转向极化强度△ε2逐渐减小,界面极化占主导作用且其占主导作用的频宽△f随M升高逐渐变宽。界面极化弛豫时间常数τ1与M呈线性指数关系,可通过τ1与M的关系式消除环境湿度对定子线棒绝缘频域介电谱的影响。同时,对线棒试样进行浸水试验得到不同水分含量的线棒试样,并进行FDS测试;制作不同厚度的发电机环氧云母绝缘材料试样,并在不同温度下对环氧云母绝缘材料试样进行吸湿试验。利用Fickian定律对环氧云母绝缘试样吸湿过程进行拟合分析,结果表明:环氧云母绝缘吸湿过程主要由环氧树脂吸湿和复合绝缘材料界面吸湿两个过程叠加,环氧云母绝缘初始阶段吸湿主要是环氧树脂吸湿,界面吸湿饱和率高于环氧树脂饱和吸湿率。当环氧云母材料充分吸湿后,环氧云母绝缘吸湿后水分主要存在于材料界面处,使得在FDS测试过程中高水分含量的定子线棒绝缘界面极化强度增大,从而在ε"介电谱中将出现局部弛豫峰。在发电机检修过程中应该定期检测水冷却通道的流通性,并定期对绕组表面进行除潮处理,避免水分进入到绝缘内部而降低定子绕组绝缘的寿命,为发电机的维护提供重要的实际参考价值。
[Abstract]:As the main power equipment in power system, generator stator insulation system is one of the key parts of generator. The dielectric response method used in recent years provides a new idea for the evaluation of the insulation state of the generator, and the existence of moisture will seriously affect the test results of the stator insulation of the generator. At the same time, moisture is one of the important factors to accelerate the insulation aging of generator stator. It is important to study the insulation and moisture absorption characteristics of generator stator for the safe operation of generator and accurate diagnosis of stator insulation state. The expressions of tangent value of dielectric loss angle, real part and imaginary part of complex dielectric constant in dielectric spectrum in frequency domain are derived by mathematical formula. The single relaxation Debye model and multiple relaxation Cole-Cole model are introduced into the relaxation model. A multirelaxation Cole-Cole model with DC conductance is established to analyze the relaxation process of dielectric frequency domain measurement results. The results show that the multirelaxation Cole-Cole model with DC conductance is more suitable than the single relaxation Debye model. In the process of dielectric relaxation of composite dielectric, the ageing of generator stator bar is accelerated by setting up a generator stator rod aging platform. The humidity box is used to control the environmental humidity of the stator bar (M) and the frequency domain dielectric response (FDS) test platform and the traditional resistance are built. The capacitance test platform is used to test the stator bar with different humidity. According to the traditional insulation resistance, The conventional time constant 蟿 0 is obtained from the capacitance test results, and a double relaxation Cole-Cole model with DC conductance is established to fit and analyze the FDS test of generator stator bar. The results show that the drying boundary is obtained by using 蟿 0 measured at different temperature and humidity state. The dry boundary can be used to determine whether the stator rod insulation is dampened or not, and the double relaxation Cole-Cole model has a good fitting result for the stator bar FDS test results, and with the increase of M, the polarization intensity 蔚 I of the interfacial polarization increases gradually at the frequency of 10 ~ (-3) ~ 103Hz. However, the polarization intensity 蔚 2 of the dipole turn decreases gradually, and the frequency width f of the interfacial polarization dominates and widens with the increase of M, and the relaxation time constant 蟿 1 of the interfacial polarization shows a linear exponential relationship with M. The relationship between 蟿 1 and M can eliminate the influence of environmental humidity on the dielectric spectrum of stator rod insulation in frequency domain. At the same time, the wire rod sample with different moisture content can be obtained by immersion test and FDS test is carried out. Epoxy mica insulation samples with different thickness were made and moisture absorption tests were carried out at different temperatures. The moisture absorption process of epoxy mica insulation samples was analyzed by Fickian's law. The results show that the moisture absorption process of epoxy mica insulation is mainly superimposed by epoxy resin moisture absorption process and composite insulation material interface moisture absorption process, epoxy mica insulation moisture absorption stage is mainly epoxy resin moisture absorption. When epoxy mica material fully absorbs moisture, the moisture of epoxy mica insulation after moisture absorption mainly exists at the interface of the material. As a result, the polarization intensity of the stator bar insulation interface with high moisture content increases during the FDS test, so that the local relaxation peak will appear in the 蔚 "dielectric spectrum. The flowability of the water-cooled channel should be tested regularly during the maintenance of the generator. In order to avoid moisture entering into the insulation and reduce the life of stator winding insulation, this paper provides an important reference value for generator maintenance.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM31

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