共查询到20条相似文献,搜索用时 15 毫秒
1.
为了研究低压穿越对1.5 MW双馈感应式风力发电机(Doubly Fed Induction Generator,DFIG)绝缘老化的影响和使绕组绝缘性能降低的因素,文章对电老化、热老化和机械应力老化模型进行分析。综合PSCAD和Ansoft仿真得到的低压穿越过程中电流、电压、转速等物理量的变化,以及不同低穿程度下发电机铁耗和铜耗反映出的铁芯和绕组的生热情况,利用老化模型判断低压穿越对绕组的绝缘性能产生的影响,进而分析其对匝间短路的影响。分析结果表明,低压穿越会对绕组绝缘性能产生恶劣影响,极有可能造成发电机匝间短路故障或者使故障恶化。 相似文献
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Partial discharges (PDs) occur in the air-filled gaps of enameled wires that are touching. They erode the insulation and consequently lead to an interturn breakdown. This paper describes the failure mechanism of low voltage interturn insulation as a consequence of PDs and shows why and how it is influenced by the insulation design, temperature, and the applied voltage. Understanding the failure mechanism leads to better founded maximal permissible stresses and a proper design of the interturn insulation to avoid premature drive failures 相似文献
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Okubo H. Hayakawa N. Montanari G.C. 《Dielectrics and Electrical Insulation, IEEE Transactions on》2007,14(6):1516-1530
This paper reviews the up-to-date research activities on electrical insulation techniques under repetitive surge voltages with steep wavefront for low voltage inverter-fed motors. Partial discharge (PD) inception, propagation, ageing and breakdown characteristics of magnet wires, including recently developed PD-resistant wires such as nanocomposite enameled wires, are described. PD measurement techniques under the steep-front voltages and IEC activity toward their standardization are also introduced. 相似文献
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为了分析耐电晕漆包线在电机实际使用过程中的耐电晕性能,通过拉力试验机模拟耐电晕漆包线使用过程中的拉伸情况。首先通过拉力试验机对耐电晕漆包线进行拉伸,拉伸率分别为10%、15%。然后分别进行未拉伸漆包线、拉伸率10%及15%的耐电晕漆包线的击穿电压试验和耐电晕性能试验,并进行漆包线拉伸前后击穿电压和耐电晕寿命的比较。结果表明:拉伸率为10%、15%后漆包线击穿电压与未拉伸试样相比略有下降,拉伸15%后漆包线的击穿电压保留率超过85%。拉伸率为10%、15%的漆包线耐电晕性能与未拉伸试样比较有较明显的下降,拉伸率为15%的漆包线的耐电晕性能略差于拉伸率10%的漆包线,耐电晕漆包线拉伸率为10%时,其耐电晕性能保留率不足20%。 相似文献
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《Dielectrics and Electrical Insulation, IEEE Transactions on》2008,15(6):1617-1625
Effects of ambient humidity and temperature on partial discharge (PD) characteristics in twisted pairs with conventional and nanocomposite enameled magnet wires have been investigated. Measurements of the PD inception voltage (PDIV) and the apparent PD charge were performed by applying an ac sinusoidal waveform voltage of 60 Hz to the twisted pair. The observed PDIV in this study can be classified into the following three behaviors. First, the PDIV in both wires decreases with increasing relative humidity (RH) at low temperature. Secondly, the PDIV in both wires slightly increases when increasing the RH at high temperature. Thus, there is a certain value of the absolute humidity to determine the lowest PDIV in both cases with the conventional and nanocomposite enameled wires. Thirdly, the PDIV in the conventional enameled wire significantly decreases at the RH of 95 %, while the decrease rate of that in the nanocomposite enameled wire is relatively small. The observed PD phenomena are discussed in terms of material characterization of the enameled wires such as changes in permittivity due to moisture absorption and wettabilitiy under voltage application. 相似文献
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Haq S.U. Jayaram S.H. Cherney E.A. 《Dielectrics and Electrical Insulation, IEEE Transactions on》2007,14(2):417-426
The paper presents the experimental results on accelerated aging of enameled wires with and without nanofiller in the coating under partial discharge (PD) activity. The residual life of the wires, and the surface roughness as measured by a scanning electron microscope (SEM), are used to evaluate the effects of the nanofiller. The surface erosion in the specimens without nanofiller is considerably greater, which is 1120-1270 nm, under pulse aging; whereas, in specimens with ~1%, by wt, fumed silica (SiO2) nanofiller it was measures to be 230-250 nm. An evaluation of the residual life of the wires, aged under high frequency AC waveforms, reveal that the wires with SiO2 achieved a life that is twice the life of conventional wires. The two-parameter Weibull distribution of dielectric strength data show that the value of the shape parameter, beta, increases from 2.6 to 11.4 for the coatings with nanofillers indicating that the material becomes more homogeneous and exhibits fewer defects. Finally, the paper discusses possible reasons for the reduction in surface erosion and improvements in breakdown strength of enameled wires filled with various types and concentrations of nanofillers 相似文献
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Bamji S.S. Tohyama K. Bulinski A.T. 《Dielectrics and Electrical Insulation, IEEE Transactions on》1999,6(3):288-294
Underground power cables in service are inadvertently subjected to impulses generated by lightning and switching surges that are superimposed on the ac voltage at which they operate. HV transients caused by lightning and switching operations not only radiate large electromagnetic fields but also impose additional stresses on the insulation and could initiate deterioration which can continue under normal operating conditions. Electrical breakdown of HV cables is a local phenomenon and electrical aging at local sites in the polymeric insulation occurs by molecular dissociation of the polymer and formation of new chemical bonds. This process usually involves the electronically excited states of the molecules that give rise to radiative phenomena, such as electroluminescence (EL). Analysis of EL can help to clarify the degradation mechanisms that occur at points of electrical stress enhancement and lead to cable breakdown. The EL technique is several orders of magnitude more sensitive than the commonly employed partial discharge detection and can provide a better understanding of the various time dependent mechanisms such as space charge injection, trapping and decay that can lead to insulation failure. The characteristics of EL in crosslinked PE subjected to impulse voltage, are described in this paper. Impulses having the same polarities as the half cycles of the ac voltage on which they are superimposed give rise to the largest number of EL pulses. Also, more EL pulses are emitted when impulses are applied at the peaks of the positive and negative half cycles than at the zero crossing of the ac voltage. This suggests that the amount of charge injected and trapped into the polymer plays a crucial role for EL emission 相似文献
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基于介质损耗分析研究变频电机绝缘老化特性 总被引:1,自引:1,他引:1
变频牵引调速电机匝间绝缘承受来自逆变器的连续高压脉冲方波的作用,其老化机理与工频正弦电压作用下具有很大差异。笔者通过采用两种电压源对模拟变频电机匝间绝缘和对地绝缘的绞线对试样进行老化试验,测量了tanδ随老化时间的变化趋势,分析了电压形式对匝间绝缘和对地绝缘介质损耗产生和发展的作用机理。试验结果表明:脉冲电压下,匝间绝缘内部有放电发生时,放电与空间电荷协同作用使绝缘缺陷迅速增多;无放电时空间电荷反复注入和抽出造成绝缘损伤。交流电压下绝缘介质发热主要由局部放电造成,而脉冲电压下主要是由空间电荷所导致。对地绝缘由于其绝缘结构,呈现槽放电现象,空间电荷的引入大大加速了绝缘的老化。 相似文献
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基于局部放电统计参量的脉冲电压下绝缘老化分析 总被引:2,自引:0,他引:2
主要针对匝间和对地绝缘电磁线在脉冲电压下老化后的局部放电特征进行了研究.通过不同老化时间的局部放电相位相关分析,在高频脉冲电压下老化后放电次数相位分布出现明显的"放电丛"现象,并通过工频老化后的局部放电结果对此加以证实.通过两种不同电磁线老化特征对比,匝间绝缘和对地绝缘呈现不同的放电特征,匝间主要以内部气隙放电为主,而对地绝缘电磁线则以槽放电为主.此外,测量和分析了局部放电统计参量(如偏斜度、峭度、不对称度等)随老化时间的变化,结果表明平均放电量的偏斜度和老化时间有着一定联系.为更深入地研究脉冲电压下绝缘老化机理打下了坚实的基础. 相似文献
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为解决铁心电抗器匝绝缘无法有效进行耐压试验的问题,本文提出谐振高频法匝绝缘试验方法,文中通过比较分析阐明高频法的优越性,给出试验电压选择依据,并给出试验电流和频率关系,提出满足串、并抗的试验频率范围。通过理论分析得出了串联谐振下的逆变方波电源输出端电压和试品电抗器端电压的解析表达式,并对谐振条件检测与频率调谐进行时域同步算法分析。文中搭建谐振高频法匝绝缘耐压试验系统,分析串联电抗器串并联混合补偿电容主要参数关系,给出对应的谐振试验回路关键元件参数选取原则。实验结果表明,本文谐振高频法可实现铁心电抗器匝间绝缘缺陷有效检测,为实际工程应用提供重要的参考。 相似文献
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干式变压器绕组发生轻微匝间短路时,相电压、相电流等电气量变化甚微,不能作为表征匝间短路故障的敏感特征量,导致相应保护措施缺失,运行过程中设备烧毁事故时有发生。通过建立干式变压器“场-路”耦合仿真模型,利用实际试验和工程计算获取的状态参数,验证模型的准确性。通过建立和分析其绕组匝间短路故障数学模型,提取相电压、相电流不平衡度标幺值的差值,作为判断匝间短路故障的特征量。通过仿真分析不同工况下其绕组发生匝间短路故障时不同电气量的变化情况,论证了所提新故障特征量不仅能提前感知绕组匝间短路故障,而且能够克服固有的三相不对称及不平衡运行带来的影响,有效性、灵敏性兼顾,为实时监测干式变压器绕组匝间绝缘状态提供一种新方法。 相似文献
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在实践经验的基础上,分析了我国匝间绝缘短路的主要原因,提出在匝间绝缘的设计,制造工艺及耐压试验等工序采取合理措施,以提高匝间绝缘的可靠性。 相似文献
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Correlation between trapping parameters and surface insulation strength of solid dielectric under pulse voltage in vacuum 总被引:1,自引:0,他引:1
Wen-Bin Zhao Guan-Jun Zhang Yun Yang Zhang Yan 《Dielectrics and Electrical Insulation, IEEE Transactions on》2007,14(1):170-178
As well known, the surface conditions of solid materials strongly affect the flashover phenomena under high electric field. The artificial doping ingredients could change the energy distribution and the density of electron and hole traps. The trapping parameters in the surface layer have some influences on the surface insulation strength. In order to adjust different trapping parameters, the composite materials of epoxy resin intermingled with aluminum hydroxide are prepared. The trapping parameters of the samples with different filler concentrations are investigated through the method of measuring the surface potential based on the isothermal current theory. The surface insulation performance in vacuum of each sample is tested according to the flashover voltage under pulsed excitation. Based on the experiment, the correlation between the trapping parameters and surface insulation strength is discussed and some novel models are presented 相似文献
16.
Fabiani D. Montanari G.C. Cavallini A. Mazzanti G. 《Dielectrics and Electrical Insulation, IEEE Transactions on》2004,11(3):393-405
It has been observed that voltage waveforms generated by power electronic converters may affect significantly the reliability of electric motor insulation. Since partial discharges are considered to be the main cause of the reliability loss, new enamel insulations for magnet wires are being developed in order to withstand better stress amplification. The electrical characterization of these insulating materials is often carried out through aging tests which may provide estimation of life under different stress levels and conditions. However, deeper investigation of aging phenomena due to supply voltage waveforms is needed, especially regarding the relation between aging factors and stress conditions. This paper deals with this topic, showing experimental evidences of relation between partial discharge quantities (e.g., inception voltage, repetition frequency, amplitude) and electrical properties, associated with charge accumulation, which can be directly evaluated through space charge measurements. Characterization of insulating materials and comparison of materials candidate for application in power electronic waveform environment can be carried out resorting to the methodology proposed here. This approach can provide, therefore, a useful feedback to wire manufacturers regarding, e.g., the choice of additive nature and enamel components for magnet wires in power-electronic controlled motors. 相似文献
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The authors obtained and quantitatively evaluated V-N characteristics and the time variation of remaining thickness of nanocomposite enameled wires under repetitive surge-voltage application. V-N characteristics exhibited longer times to breakdown for nanocomposite enameled wires and the PD resistance increased with increasing nanofiller concentration. In the case of conventional enameled wires, the remaining enamel thickness decreased linearly with the time of voltage application, i.e., with increasing total number of PD generated, N, and the enamel thickness was eventually bridged, i.e., BD. In the case of nanocomposite enameled wires, the remaining thickness reached a plateau after a gradual deterioration in the first stage, which could contribute to the longer time to BD compared to that of conventional enameled wires. The resistance to deterioration in depth could have brought about the expansion of deterioration in the peripheral and longitudinal directions of nanocomposite enameled wires. 相似文献
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基于数字局部放电检测的大型电动机主绝缘老化特性的研究 总被引:5,自引:0,他引:5
大型电动机在长期的运行过程中,要遭受电,热,机械等多因子应力的联合作用,使主绝缘逐渐老化,为了研究主绝缘老化机理,评估其剩余寿命,需要对电动机定子线棒进行多因子应力综合老化试验,并寻找能反映主绝缘老化程度的特征参量;本文采用先进的数字局部放电检测技术对不同老化阶段的试样线棒进行了综合测试,分析了局部放电各参量与试样线棒老化程度的关系,给出了各种反映绝缘老化特性的指纹图形,测试结果表明,随着试样线棒的进一步老化,局部放电量,放电次数,放电能量呈增长趋势,最大放电脉冲相位产生偏移,其偏斜度由大变小,这为评定大型电动机主绝缘的剩余寿命提供了参考依据。 相似文献