振动频响法与传统频响法在变压器绕组变形检测中的比较

首先详细介绍了振动频响法(vibration frequency response analysis,VFRA)检测原理,并与传统频响法(frequency response analysis,FRA)进行了对比。然后对一台220 kV变压器绕组进行了多种人工故障设定,并利用振动频响法与传统频响法对所设故障进行对比检测分析。试验结果表明,振动频响法相比传统频响法对绕组预紧力下降、垫块脱落、幅向轻微变形等故障具有更高的检测灵敏度。

振动频响分析法在大型变压器绕组变形检测中的应用

对一台220 kV变压器A相绕组前后相隔3天的扫频数据进行比较,并对C相绕组人为制造垫块脱落和绕组径向变形故障,以对比其故障前后的扫频结果.结果表明,振动频响分析法能够有效检测绕组变形故障,其重复性较好,且灵敏度比短路阻抗法更高.

基于振动频响法的变压器绕组变形检测

为了更加有效地识别绕组的变形故障,在基于机械振动频响法对变压器绕组进行检测的基础上,提出了标示绕组形变程度的振动频响曲线相关系数。通过对大型变压器的绕组进行人为故障设定,利用机械振动频响法对故障绕组进行检测,试验证明该振动频响曲线相关系数对判断变压器绕组变形具有较高的灵敏度。

基于土层振动频响函数预测地铁环境振动的频域解析方法

根据土层振动频响函数反映土层固有特性的原理,提出基于土层振动频响函数预测地铁环境振动的频域解析方法。首先采用车轨解析模型计算得到作用于隧道基底的系列频域力;然后采用土体解析模型计算得到系列频域力作用点处到地面预测点处的系列土层振动频响函数;再根据土层固有特性不随输入荷载大小而改变的性质,将单个频域力与其对应的土层振动频响函数进行复数相乘,得到单个频域力作用下地面预测点处的振动响应;最后将各作用点处振动响应累加得到地面预测点处的振动响应。采用此方法预测北京地铁1号线东单站至建国门站区间由地铁列车运行引起的地面振动响应,并利用现场地面振动测试数据进行验证。结果表明:预测的地面振动加速度时程波形及频谱波形、地面振动1/3倍频程加速度级曲线和Z振级均与现场实测结果基本一致;该预测方法具有计算速度快、预测精度高、预测频带宽等特点,可以有效地预测地铁运行引起的环境振动响应。

旋转柔性梁系统振动频响特性分析及振动抑制

航天器挠性附件或柔性机器人等柔性旋转梁系统的模态阻尼小,由于扰动,或者在调姿及转动时,大幅值的振动将持续很长时间,这将影响系统的稳定性和指向精度,因此,必须对振动进行主动控制。提出一种基于加速度传感器反馈的复合控制算法,快速控制系统设定点及转动过程的振动。建立挠性旋转梁试验平台,进行了基于加速度传感器和压电片传感器的试验模态激励分析、振动频响特性分析。并根据振动特性选取加速度反馈控制算法的相应参数,利用交流伺服电机驱动器抑制旋转梁设定点的振动、旋转过程的振动主动控制进行了试验研究。试验结果表明采用提出控制方法能够快速地抑制系统的振动,验证了特性分析和提出控制方法的可行性。

振动频响法变压器绕组状态检测试验研究

以一台110kV变压器为研究对象，采用变压器振动频响测试系统，对变压器绕组正常与典型故障下的振动频响特性进行了试验研究。本文所提出的方法相对现今变压器绕组故障诊断缺乏有效的检测手段而言，是一个非常有效的补充。根据箱壁上多个测点处的振动频响曲线，分析变压器绕组状态。试验结果进一步验证了变压器绕组振动扫频试验的可重复性。相对于频响分析法，变压器绕组的振动频响曲线能准确检测出变压器绕组的松动与变形故障。

大型变压器绕组振动频响特性的试验研究

为更加准确地理解和掌握变压器绕组的振动响应特性,及时发现变压器绕组的故障隐患,以一台110 k V变压器为研究对象,依托所研制的变压器振动频响测试系统,对变压器绕组正常与典型故障下的振动频响特性进行了试验研究,根据箱壁上多个测点处的振动频响曲线,基于信息融合的思想计算分析了变压器绕组融合振动频响曲线的归一化奇异谱熵。试验结果进一步验证了变压器绕组振动频响试验的可重复性。变压器绕组振动频响曲线峰值随频率的增加而增大,且其峰值点随绕组工况不同出现明显偏移。归一化奇异谱熵能够较好地对变压器振动频响曲线进行定量描述,当变压器绕组存在松动或变形等典型故障时,振动频响曲线的归一化奇异谱熵变化率均〉5%。

基于振动频响法的变压器绕组松动故障检测方法研究

变压器是电力系统的重要设备,在长期运行中会出现绕组松动、变形等故障,影响电力系统的正常工作,因此对变压器绕组健康状态进行评估极为重要。提出利用振动频响法获取变压器绕组的振动频响函数,对比绕组故障状态与健康状态下的振动频响函数,将两者之间的相关系数作为判断变压器绕组故障与否的依据。随后,对比健康状态与4种不同程度松动状态下变压器绕组的振动频响函数,探讨利用相关系数判断变压器绕组松动故障程度的可行性。本研究结果对判断变压器绕组运行故障具有一定的指导意义。

基于振动频响法的变压器绕组离线检测

介绍了变压器振动频响法原理,对一退役220kV变压器C相绕组设置一系列故障并进行振动频响试验,从试验数据中提取量化绕组状态变化的特征量,结果表明振动频响法检测绕组状态相对短路阻抗法有很高的灵敏度。

振动频响法VFRA在主变绕组变形检测中的应用研究

阐述了振动频响法是利用变压器绕组机械频响函数检测绕组变形的方法。验证了该方法具有良好的重复性,在A、B、C三相分别模拟轴向预紧力下降,幅向受力改变,轴向垫块脱落与幅向变形的故障,通过图像对比和计算说明振动频响法对绕组变形故障反应十分敏感,故障前后频响曲线相关系数最高为0.99,与传统方法相比有明显的优势。

地下结构纵向随机地震响应和极值分析

应用弹性地基梁理论 ,建立了地下结构的纵向振动频响函数方程 ,并将地震运动作为随机过程 ,同时又考虑地震动的空间变化因素 ,研究了地下结构的平稳和非平稳纵向地震随机响应以及在一定置信度条件下的极值反应 .

某MPV车型中排座椅怠速振动控制研究

文章研究三缸发动机MPV车型怠速工况下中排座椅的振动性能。阐述分析怠速座椅振动的激励源特性、整车传递路径特性和座椅响应,研究坐人和不坐人对座椅模态频率和振动频响幅值的影响,以及座椅模态频率和振动频响幅值对怠速抖动的影响。结果表明,座椅坐人相对不坐人模态频率升高,头枕杆振动频响幅值下降。文章制定了头枕杆振动设计目标和座椅NVH前期控制目标,坐人的座椅模态频率与激励频率需避开3 Hz,头枕杆振动频响幅值需小于0. 55 m/s^2。

基于熵权关联理论的变压器绕组松动状态的振动检测法

为更加准确地检测变压器绕组的故障隐患,从变压器绕组多个测点处振动频响曲线的相关性出发,提出了一种综合灰色关联分析和熵权理论的变压器绕组振动检测方法。首先基于灰色理论计算了各个测点处振动频响曲线的灰色关联度和灰色面积关联度,然后定义了熵权关联度对变压器绕组状态进行检测。对某220 k V变压器绕组正常与松动时的振动频响试验结果进行了分析,结果表明,所定义的熵权关联度的计算结果与变压器预设工况吻合良好,可以较好地描述变压器绕组的松动状态,具有较好的工程应用价值。

基于熵权关联理论的变压器绕组状态振动检测

为更加准确地检测变压器绕组的故障隐患,本文从变压器绕组多个测点处振动频响曲线的相关性出发,提出了一种综合灰色关联分析和熵权理论的变压器绕组振动检测方法。该方法根据某220kV变压器绕组正常与松动时的振动频响试验结果,首先基于灰色理论计算了各个测点处振动频响曲线的灰色关联度和灰色面积关联度,然后定义了熵权关联度对变压器绕组状态进行检测。结果表明,所定义的熵权关联度的计算结果与变压器预设工况吻合良好,可以较好描述变压器绕组的松动状态。与现有的频响分析法相比,振动频响法能更为灵敏地检测出变压器绕组的松动状态,具有较大的工程应用价值。

110 kV电力变压器绕组模态研究

变压器绕组等效的机械结构体,一旦发生改变,其模态将发生相应变化,此时对其振动信号进行频率响应分析,即可检测绕组轻微变形。对变压器绕组进行模态分析:利用ANSYS对绕组进行幅向建模分析,分别得到了绕组故障与正常情况下频响曲线的变化规律。开展真实110 kV变压器模态实验,并与ANSYS仿真结果对比,进一步验证了仿真结果的正确性,同时,为下一步研制振动检测系统奠定了基础。

Research on velocity and acceleration geophones and their acquired information

Based on the research of two geophone types （10 Hz moving-coil velocity and piezoelectric acceleration） and their velocity and acceleration parameters, frequency response functions have been determined, as well as the differences between them. Also, shock- vibration tests have been accomplished, not only to explain the two shock response signal differences, but also to analyze the response signal characteristics and its ability to carry information. In addition, seismic data acquisition experiments have been carried out under comparable conditions in the field. A contrast analysis of shot gathers and stack profiles acquired with the two geophone types is given in this paper. The results show that the acceleration signal from the acceleration geophone has a better advantage in terms of high signal-to-noise ratio, high accuracy, high resolution, and quantity of information to better meet current and future requirements for seismic exploration.

EXPERIMENTAL MODELING OF MIDDLE-RISE BUILDING VIA AMBIENT MODAL IDENTIFICATION

Experimental modeling of a middle-rise office building via ambient modal identification is presented. A 200-DOF (Dimension of freedom) test model is designed to correlate with finite element mode. A newly developed frequency-spatial domain decomposition ( FSDD ) technique is used to identify modal characteristics of the full-size building by using ambient response measurements. In the interested frequency ranges of 0～4.5 Hz and 0～ 6.5 Hz altogether 9 bending and torsion modes are identified. As one of the major focuses of the project, the accurate damping estimation is conducted based on FSDD. The identified modal frequencies and mode shapes are utilized for finite element model tuning. Excellent agreement has been achieved with respect to the final tuned finite element (FE) model up to 9 modes.

Development of an Accurate Numerical Methodology for Predicting the First Three Modes of Vibration of an Electric Motor Fixed on a Rigid Base

This paper proposes a numerical methodology for the prediction of the first three modes of vibration of an electric motor fixed on a rigid base. A deep literature review supported the production of four ad hoc prototypes that aided the development of the proposed approach. Tests carried out with the prototypes led to the procurement of the modal parameters be used to calibrate the numerical models, as well as the FRF （frequency response function） curves be used to validate the numerical solution. The validated model allowed structural changes to be then promoted on the prototypes, in order to make them more robust to variations in manufacturing and assembling processes. The mentioned adjustments and structural changes were accomplished by means of a process of structural optimization using Genetic Algorithm. The solution was developed based on the commercial finite element code ANSYS. The practical results obtained in this study show that a numerical model for modal analysis of an electric motor fixed on a rigid base with errors less than 3% for the first three modes of vibration can be achieved, allowing positive structural changes to be performed in the machine design that result in the minimization of manufacturing reworks associated with the dynamic behavior of the studied motor.

Vibration transmissibility characteristics of smart spring vibration isolation system

The objective of this work was to study the vibration transmissibility characteristics of the undamped and damped smart spring systems. The frequency response characteristics of them were analyzed by using the equivalent linearization technique, and the possible types of the system motion were distinguished by using the starting and ending frequencies. The influences of system parameters on the vibration transmissibility characteristics were discussed. The following conclusions may be drawn from the analysis results. The undamped smart spring system may simultaneously have one starting frequency and one ending frequency or only have one starting frequency, and the damped system may simultaneously have two starting frequencies and one ending frequency. There is an optimal control parameter to make the peak value of the vibration transmissibility curve of the system be minimum. When the mass ratio is far away from the stiffness ratio, the vibration transmissibility is small. The effect of the damping ratio on the system vibration transmissibility is significant while the control parameter is less than its optimal value. But the influence of the relative damping ratio on the vibration transmissibility is small.

变压器绕组状态检测系统全频段恒流激振电源

为变压器绕组状态检测系统研制一种全频段输出恒定电流的激振电源。基于ACDC-AC结构,设计整流模块和基于IGBT的逆变桥模块,搭建CPLD和DSP协同的控制电路,在MATLAB/Simulink下实现恒流源的PI控制。经现场测试,该电源在30~350 Hz频率范围内连续可调,最大输出电流40 A,频率绝对误差小于0.2 Hz,总谐波失真率小于2%。完全满足了变压器绕组振动频响检测技术的大功率扫频要求。