频率响应法在变压器绕组变形诊断中的应用

变压器绕组存在变形的情况下,在较大电动力冲击时,变压器内部发生短路故障的概率大幅增加,严重威胁变压器运行安全。本文介绍了频率响应法的基本原理及分析判断方法,并结合实际案例运用纵向或横向比较法及相关系数值对变压器绕组变形情况进行综合分析。结果证明,频率响应法是判断绕组是否变形的有效分析方法,该方法能有效判断绕组变形的类别及严重程度,分析出是匝间短路、局部变形,还是整体位移等具体变形情况。     

变压器绕组变形现场试验与分析

简要介绍了变压器绕组变形的原因,对比分析了测试绕组变形的方法。对交接试验中4台变压器的频响试验数据进行了横向对比、分析和计算,并提出了在变压器受到短路电流冲击后判断绕组变形的方法。     

频响法在变压器绕组变形检测中的应用

频响法是由变压器绕组一端注入扫频信号,然后通过测量绕组两端特性参数,分析其频域图谱特性,判断变压器绕组是否变形的一种新方法。它比低压脉冲法易于实施,且测得的图谱较稳定;它与短路阻抗法相比,对影响变压器变形的分布电感和电容更为灵敏。在详细分析了频率响应法测试变压器绕组变形的全过程和测试过程中的影响因素后,结合在某供电公司现场获取的实际数据和曲线,进行了分析、判断,其结果与吊芯检查相吻合。     

频率响应法在变压器绕组变形测试中的应用

电力变压器是电力系统的主要设备之一,进行变压器绕组变形测试对正确判断变压器在受到冲击力后是否产生绕组变形,从而保障变压器的安全运行具有重要意义。本文介绍了应用频率响应法对变压器进行绕组变形测试的原理、方法,对现场开展变压器绕组变形测试、确保电网安全运行具有指导作用。     

检测变压器绕组变形的低压脉冲法的研究

对变压器绕组变形的低压脉冲检测法进行了研究。简要介绍了低压脉冲法检测绕组变形的基本原理，对影响低压脉冲法检测变压器绕组变形测试结果的因素进行了考察，并利用测试系统对模拟不同部位、不同种类变形故障的模型变压器进行了测试，提出可根据变压器绕组时域响应波形的畸变及变压器传递函数频谱图的变化来判断变压器绕组是否发生变形故障。     

两项检查变压器绕组变形的试验

介绍了变压器绕组电容测试和短路阻抗试验两个判断变压器绕组变形的试验及判断方法,通过对故障变压器试验及吊罩结果的分析,证明两个方法可以与变压器绕组变形试验结合判断绕组变形程度。     

FRAMIT绕组频率响应测试仪工作原理及应用

阐述了FRAMIT绕组频率响应测试仪的基本工作原理,给出了绕组变形的判断依据和方法,并对变压器绕组图谱进行了实例分析.     

短路阻抗法在变压器绕阻变形测试中的应用

短路阻抗是变压器的一个重要特性参数,决定了变压器在系统短路时短路电流的大小及变压器内部的电动力的大小。在变压器受短路冲击时,通过短路阻抗试验及绕组变形试验可检测出该受冲击变压器是否受变形。当变压器已发生变形时可通过测试变压器的单相漏抗来判断冲击变压器绕组发生变形相。     

一起电力变压器绕组变形的综合分析

介绍了一起变压器绕组变形的判断分析过程,总结了进行绕组变形测试的注意事项。     

变压器绕组变形综合测试法研究应用

介绍了变压器绕组变形测试中的频率响应法、低压短路阻抗法和电容法的原理、判断方法、优缺点,并通过一台110 k V变压器绕组变形测试及解体试验的案例,提出了变压器绕组变形综合测试法,证明了单一的测试方法并不能保证准确的判断变压器绕组变形情况,综合测试法有更高的诊断效率和准确性。     

影响变压器频率响应测试结果的因素分析

为消除电网中变压器绕组变形引起的事故隐患，章根据频率响应法在嘉兴电网中应用的实际情况，在4年多的时间内对所辖的500kV主变压器1台／次、220kV主变压器28台／次，110kV主变压器156台／次进行了多次现场测试，研究得出了在现场应用该方法测试对变压器绕组变形的频响曲线几种影响因素，同时，提出利用频响法测绕组变形的注意要点。     

Modeling of multiwinding transformers using phase coordinates

We propose a method for modeling multiwinding transformers in phase coordinates. Based on this approach, it is possible to build mathematical models of transformers with any winding diagrams that are applicable in practice. This method also allows for the closure of magnetic fluxes on tank walls. Furthermore, the method adequately represents processes in transformers subject to asymmetrical conditions.     

基于振动信号分形维数的变压器松动诊断方法

基于变压器松动前后振动信号非线性特性的改变,提出采用振动信号时域波形的分形维数作为铁心、绕组松动诊断特征量。文中探讨了分形维数应用于变压器振动信号分析的可行性,根据分形理论,针对变压器振动模拟信号与实测信号分别进行了分形盒维数计算。结果表明,正常状态下不同变压器绕组振动信号分形盒维数集中于1.19,不同变压器铁心振动信号分形盒维数不同,但对于同一台变压器,其铁心振动信号分形盒维数具有稳定值。变压器松动故障后,铁心和绕组振动信号的分形维数均明显增大,分形维数能准确反映变压器正常与松动状态。     

Transfer function-based partial discharge localization in power transformers: a feasibility study

Statistical studies have shown that failures of bushings, winding insulation, and online tap changers are the main causes for long-duration outages of transformers. This article investigates the development of an instrument for supervising the conditions of transformer units. The use of sectional winding transfer functions (SWTFs) for online PD evaluation in power transformers has several advantages: localization of PD sources, discrimination between PDs inside or outside of the transformer, and evaluation of actual PD amplitudes along the winding. Direct measurement of SWTFs-when different points along the coil are accessible-and use of these SWTFs for PD evaluation and localization has shown excellent results. In order to use this method at transformers on site, an appropriate modeling method is needed for the computation of the SWTFs using only measurements at the transformer terminals. A detailed modeling approach based on discrete RLC circuit elements has been studied and different algorithms used for parameter estimation and optimization. This model is applicable in practical cases for a limited frequency range if genetic algorithms (GAs) are used for parameter optimization. A new method based on traveling wave theory has been investigated using genetic algorithms to search for the optimum parameters of a partial differential equation that describes the transient behavior of the coil. This method has shown potential in solving SWTF calculation problems for different transformers.     

一种直接消除变压器合闸励磁涌流的方法

变压器在轻载或者空载的情况下合闸通电,可能导致一次绕组流过励磁涌流。涌流出现的原因在于变压器铁心因合闸角、剩磁等各种条件的综合作用而进入饱和区甚至是深度饱和区。励磁涌流对变压器自身和电网的电能质量都有不利影响,本文提出了一种基于二阶欠阻尼电路和分压器组成的涌流抑制器,来消除变压器合闸时刻出现的励磁涌流。利用三卷变压器的第三绕组,配以"涌流抑制器"来实现施加在三卷变压器的第三绕组上的电压幅值逐渐爬升,同时保证施加在两个绕组上的电压幅值不同、但相位相同,以起到对励磁涌流的抑制作用。仿真结果证实了该方法的正确性和有效性。     

起动异步电动机用磁控式可控电抗器的建模及仿真

介绍了一种改进后的新型起动异步电动机用的磁控式可控电抗器的基本结构和工作原理。从数学分析出发得到等效电路,基于M atlab/PSB对其作了动态仿真。仿真表明将两个相同的变压器一次侧绕组串联,二次侧绕组反串联,可以准确地反映主回路的电流波形和控制回路的电压波形。     

A fuzzy ARTMAP fault classifier for impulse testing of power transformers

The work presents an artificial intelligence (AI) based impulse test technique for oil filled power transformers. Determination of exact nature and location of faults, during impulse testing of large power transformer is of practical importance to the transformer manufacturers as well as designers. The presently available impulse test techniques more or less depend on expertise of the test personnel, and in many cases lead to ambiguity and controversy. The new AI approach presented in the paper overcomes the limitations of conventional test methods. This new technique relies on high discrimination power and excellent generalization ability of fuzzy neural networks in complex pattern classification problem. The proposed method employs a fuzzy ARTMAP pattern recognition technique to recognize the frequency responses of the winding admittance of high voltage transformers under healthy and different faulty conditions of winding insulation, and learns to establish the correlations between the nature and physical location of occurrence of an internal insulation fault in a transformer winding and its associated frequency response. The technique was tested on the winding model of typical high voltage transformer and yielded high diagnostic accuracy by successful detection and discrimination of faults of different nature and different site of occurrence in the high voltage winding.     

大型变压器现场加热干燥方法的研究与应用

大型变压器现场安装过程中,防止受潮是最关键的环节。目前现场干燥处理的方法为滤油机热油循环法,处理时间长、效率低,尤其在环境温度较低时,无法加热到工艺要求温度,从而难以达到理想的干燥效果。为满足大型变压器现场干燥的需求,提出了采用短路法进行变压器的现场加热干燥,即将低压绕组短路,对高压侧绕组施加额定电流,使高、低压绕组发热,从内部将器身绝缘均匀加热到指定温度,来达到加热干燥的效果;并在此基础上,研制了适用于大型变压器的短路法现场加热干燥装置。该方法及装置已成功应用于特高压换流变压器的现场加热干燥处理,且效果显著。应用结果表明:短路法的加热功率、效率高,干燥效果好,是适用于大型变压器现场加热干燥的有效方法。     

组合法分析电力变压器端部电场及其绝缘结构

本文运用组合法──有限元法与模拟电荷法组合分析了电力变压器端部的电场，得出了影响电力变压器端部最大电场强度Ｅ＿（ｍａｘ）与其结构尺寸Ｍ、Ｈ、ρ、ｓ之间的关系，为其绝缘结构设计提供了理论依据，也为电力变压器端部电场的数值计算提供了一种新的方法。     

Can fractal techniques be used for impulse fault pattern discrimination in distribution transformers?

Distribution transformers connected to overhead lines are often prone to lightning strikes and resulting winding damage. For assessment of their insulation strength against such impulse stresses they are usually subjected to lightning impulse tests after assembly. In the case of a fault inside the winding, the shape of the winding current changes as compared to that of a healthy winding. The pattern of the fault current depends on the type of fault and its location along the length of the winding. This paper investigates the potential application of fractal techniques for analysis of such fault current patterns. Fractal features such as fractal dimension and lacunarity commonly used for image and pattern recognition have been employed for classification of distribution transformer impulse faults. Simulation results obtained for a range of distribution transformer digital models are presented to illustrate the ability of this approach to classify insulation failures during impulse testing. The proposed tool has been applied for impulse fault analysis of a scaled-down analog model of a 3 MVA transformer. The results promise potential application of this novel technique for impulse fault pattern recognition in distribution transformers.