电力变压器绕组变形故障的测量分析与判断

采用频响分析法（ＦＲＡ）测量电力变压器绕组的变形故障,具有灵敏度高、试验设备轻便、判断直观的优点。但是,频响分析法也受到诸多因素的影响,要求试验人员具有较高的测量分析能力。本文就测量方法和分析判断的一般原则提出了一些可行的原则,并对电力变压器绕组的变形故障的各种测试方法及其应用前景提出了一些建议。     

A probabilistic feature to determine type and extent of winding mechanical defects in power transformers

Frequency response analysis (FRA) is a widely-used method to detect axial displacement (AD) and radial deformation (RD) in windings of power transformers, because of its high sensitivity to small amount of mechanical defects. Interpretation of frequency response curves has been the most intricate problem of FRA method. To solve it, different numerical indices have been introduced by researchers to evaluate the frequency response of power transformers, but (1) the researchers have not discussed on genesis origin of the proposed indices and (2) most of these indices can not present a regular and linear behavior. In this paper, a probabilistic feature has been utilized to demonstrate how an efficient index originates, to diagnosis axial displacement and radial deformation in windings of power transformers. The resulted index presents a nearly linear mapping between frequency response curves and their related defect extent. To verify usefulness of this index, it has been applied to several sets of measured frequency response curves. It is illustrated that the extracted index is able to determine extent of the defects. To discriminate between axial displacement and radial deformation, local behavior of TF curves has been used.     

A novel extension method for transformer fault diagnosis

Dissolved gas analysis (DGA) is one of the most useful techniques to detect incipient faults in power transformers. However, the identification of the faulted location by the traditional method is not always an easy task due to the variability of gas data and operational variables. In this paper, a novel extension method is presented for fault diagnosis of power transformers, which is based on the matter-element model and extended relation functions. Thus, incipient faults in power transformers can be directly identified by the degree of relation. The application of this new method to some transformers has yielded promising results.     

Detection of transformer mechanical deformations by comparing different FRA connections

Frequency response analysis (FRA) is an effective technique to detect mechanical faults inside a power transformer. The FRA interpretation is normally carried out by comparing an FRA trace corresponding to a specific connection scheme with a fingerprint of its type. This paper, by contrast, proposes a novel method based on comparing FRA traces of different connection schemes recorded from the same winding to detect the mechanical deformations. In this contribution, the theoretical background is explained, and the experimental results are addressed to support the functionality of the proposed algorithm. Furthermore, a circuit model of the windings is created, and the simulation results are also used to validate the experimental measurements. Finally, two case studies describe the application of the new method in the condition assessment of transformers to achieve a more reliable decision. Although more research is needed to support the new applications, the early potential of the method is shown in this contribution.     

变压器绕组变形的频率响应分析法综述

目前对绕组频率响应的分析方法主要是基于幅频响应曲线的分析,因此从频段划分、幅频曲线特征的分析及曲线相似指数3方面综述了幅频响应曲线的研究现状,介绍了频率响应分析法的原理,从扫频范围的选择和影响测量的因素2方面讨论了绕组频率响应的测量,认为应建立原始的绕组频率响应数据库,在反映绕组变形程度的曲线相似指数研究方面有待于提出切实有效的量化标准。     

变压器绕组变形诊断中的等效模型参数辨识

提出利用变压器频响试验数据,来辨识其等效模型的参数,以此诊断变压器绕组变形。方法是：首先根据变压器电压传递函数和入端导纳函数分子、分母系娄和来粗定参数,然后把这些粗定参数作为模型参数优化的初始值,再运用“归一化”和Gauss-Newton优化方法消除误差,确定模型参数的准确值;最后可以通过辨识模型参烽的变化来诊断绕组变形。该方法在模型变压器上取得了较好的效果。     

电压响应方法在电力变压器状态评估中的应用

Power transformer is one of the most important equipment in the power system.Its operating condition affects the reliability of power supply directly.Therefore,in order to guarantee transformer operation safely and reliably,it is necessary to assess condition of power transformer accurately.Return voltage method based on voltage response measurements is still a new non-intrusive diagnosis method for internal insulation aging of transformer.In this paper the technique and application of return voltage measurement and some results of voltage response measurements of several transformers was introduced.Voltage response measurements were performed on various transformers with different voltage grades,various operating periods,different moisture contents and aging degrees on site.Derived moisture contents from return voltage measurement were compared with the corresponding moisture contents obtained from the analysis of oil samples.Based on on-site experiments and theoretical analysis,the criteria for insulation state of transformer are proposed.Moisture condition of transformer insulation can be determined by using return dominant time constant,and a good correlation between aging degree and the return voltage initial slopes of the aged transformers.Field test performed on several transformers,its interpretation of results are also presented,which proves that return voltage measurements can be used as a reliable tool for evaluating moisture content in transformer insulation.     

Improving the numerical indices proposed for the FRA interpretation by including the phase response

The frequency response analysis (FRA) is an effective technique to diagnose the mechanical deformations in a power transformer. Using the numerical indices is one of the methods proposed for the interpretation of the FRA results. Various indices have been proposed in the literature, but most of them are only based on the magnitude response of the FRA results. By contrast, this paper improves a number of the existing indices and defines a new index to include the phase response in the interpretation. The experimental data corresponding to different extents of the axial displacement and disc space variation show that including the phase response in an index increases its sensitivity. These results are also validated with simulation models of three transformers. Afterward, different uncertainties are introduced in the experiment, and it is shown that the new indices have also better performances against uncertainties in the FRA measurement. Although further studies are needed to settle the new indices, this research shows the early functionality and the potential of the phase information to improve the interpretation of the FRA results.     

Fault diagnosis of a power transformer using an improved frequency-response analysis

A transformer is one of the most important units in power networks; thus, fault diagnosis of transformers is quite significant. In this paper, the frequency-response analysis, deemed as a suitable diagnostic method for electrical and/or mechanical faults of a transformer, is employed to make a decision over a defective phase. To deal with wideband frequency responses of each phase, a synthetic spectral analysis is proposed, which augments low- and medium-frequency components, and equalizes the frequency intervals of a resulting combined curve by a log-frequency interpolation. Furthermore, for discriminating a defective phase through computing overall amounts of deviation with other phases, the two well-known criteria and three proposed criteria are examined with experiment data. The overall diagnosis results show that the proposed criterion discriminates a defective phase with the highest average hit ratio among all of the provided criteria for selected faults.     

Monitoring of power transformers using the transfer function method

The transfer function concept is well known as an additional method of evaluating the impulse test of power transformers in the test laboratory, Another application for this method is monitoring of power transformers in service. According to the method of how to measure transient signals for the calculation of transfer functions, two kinds of monitoring can be distinguished: off-line and on-line monitoring. Both kinds of monitoring as well as their influencing factors are discussed with on-site measurements on power transformers in service     

Transformer diagnosis based on two low frequencies waveforms

The health of power transformer is important for the reliability of electrical power grid. There are various methods of evaluating the frequency spectrum to confirm the presence of an incipient fault. So, the accuracy of FRA method suggested by many researchers for predictive defections, has been discussed; and the robustness (efficiency, simplicity and fast diagnosis) of the proposed 2LFW as a substitution diagnostic process has been detailed and proved. It should be noted that the proposal is general and can be applied to different transformer, without any comparison to a reference signal. Furthermore the diagnosis can be done even for transformers in operation mode (in service), thus avoiding economical losses.     

A comparison of trans-admittance and characteristic impedance as metrics for detection of winding displacements in power transformers

Transfer function signatures are commonly used in condition monitoring analysis to give early indications of winding movement in power transformers. This paper presents a comparison of the use of trans-admittance (frequency response analysis, FRA), presently the industry standard, and characteristic impedance (transmission line diagnostics, TLD), a new method, as signatures for the detection of winding displacements in power transformers. To facilitate the comparison, a computer based winding model based on a multi-phase transmission line system was developed and different winding deformations were analyzed. The results show that TLD has a higher degree of sensitivity and can be used to augment the ability to classify different types of distortions currently diagnosed by FRA.     

基于物元模型的电力变压器故障的可拓诊断方法

为了提高传统的油中溶解气体分析的诊断能力,提出了一种定性与定量相结合的电力变压器故障的可拓诊断方法。首先基于可拓学中的物元理论,建立了定性地描述电力变压器故障诊断问题的物元模型;其次引入可拓集合中的关联函数,根据故障特征定量地计算故障发生的程度;最后以195台次电力变压器为例验证了该方法的有效性。结果表明该方法能够克服IEC三比值法中无法诊断多重故障和无匹配的故障编码的不足,且具有更高的诊断准确率。     

基于模糊理论与支持向量机的变压器故障诊断方法

针对变压器结构的复杂性和故障机理的多样性,提出一种基于模糊理论和支持向量机的变压器故障诊断方法.该方法首先采用模糊理论对故障样本数据进行预处理,提取故障特征,再用支持向量机方法进行故障分类,通过采用一对多(1-a-r)的方法实现多目标分类,得出诊断结果.针对支持向量机参数不易确定的问题,采用多层动态自适应算法与k-折交叉验证方法结合对参数进行优化分析.故障诊断实例测试结果显示,该方法不仅克服了传统比值法中编码缺失、编码边界过于绝对的问题,诊断结果具有更高的准确率,而且也具有较好的适用性.     

Power transformer fault diagnosis based on dissolved gas analysis by support vector machine

This paper presents an intelligent fault classification approach to power transformer dissolved gas analysis (DGA). Support vector machine (SVM) is powerful for the problem with small sampling (small amounts of training data), nonlinear and high dimension (large amounts of input data). The standard IEC 60599 proposes two DGA methods which are the ratios and graphical representation. According the experimental data, for the same input data, these two methods give two different faults diagnosis results, what brings us to a problem. This paper investigates a novel extension method which consists in elaborating an input vector establishes by the combination of ratios and graphical representation to resolve this problem. SVM is applied to establish the power transformers faults classification and to choose the most appropriate gas signature between the DGA traditional methods and a novel extension method. The experimental data from Tunisian Company of Electricity and Gas (STEG) is used to illustrate the performance of proposed SVM models. Then, the multi-layer SVM classifier is trained with the training samples. Finally, the normal state and the six fault types of transformers are identified by the trained classifier. In comparison to the results obtained from the SVM, the proposed DGA method has been shown to possess superior performance in identifying the transformer fault type. The SVM approach is compared with other AI techniques (fuzzy logic, MLP and RBF neural network); the proposed method gives a good performance for transformers fault diagnosis. The test results indicate that the novel extension method and the SVM approach can significantly improve the diagnosis accuracies for power transformer fault classification.     

基于典型波形特征与改进DBSCAN的电压暂降同源识别方法

针对电网内单次短路故障可能触发多条母线上的电能质量监测装置记录电压暂降波形,造成电压暂降录波数据冗余、电网电压暂降水平过估计的问题,提出一种基于典型波形特征与改进基于密度的有噪空间聚类(DBSCAN)的电压暂降同源识别方法。首先,提出综合倾斜因子、波形相似度和持续时间三维特征,综合刻画电压暂降同源性;同时,研究电压暂降经多级变压器的传播特性,推导出13种变压器相电压等效传递矩阵,并提出基于Bhattacharyya距离的波形相似度计算方法。其次,利用共享近邻点(SNN)改进DBSCAN,对由三维特征构成的矩阵进行同源聚类,提出基于电网节点总数和监测点总数的聚类参数计算方法,实现电压暂降同源识别。应用实测数据和IEEE 30节点系统仿真数据进行验证,结果证明了所提方法的正确性和有效性。     

电力变压器绕组变形诊断分析

应用频率响应分析法判断变压器绕组在遭受短路冲击后是否发生严重变形具有重要的意义。介绍了频率响应法的基本原理并在大量实例的基础上,提出了横向比较分析法,即通过比较变压器三相绕组频率响应特性曲线的一致性及与同厂同型变压器绕组频率响应曲线对比来分析判断绕组变形程度;提出了定量表示2条曲线一致性的相关系数的概念,得出相关系数大小与曲线一致性的关系;提出了测试接线方法及测试过程中应注意的主要事项。     

电子式互感器合并单元的快速数据处理

结合数字化变电站对计量、保护等功能的特定技术要求,分析了电子式互感器应用中的关键问题,在此基础上阐述了数字化变电站中合并单元的数据处理功能的实现方法。文章讨论了采用Rogowski线圈的电子式电流互感器积分运算的可行方法,针对积分初值及零点漂移问题,提出预估法并采用一阶惯性环节来取代积分环节进行逐步逼近,给出了电流有效值和相位的简便计算方法。仿真分析表明,该算法与传统加数据窗口的离散傅里叶计算方法相比,可有效减少短路故障条件下电流信号的处理时间,且是可行的。此计算方法同样适用于电压信号的处理过程。     

Development and hardware implementation of a reliable protective relay data acquisition system

This paper proposes an intelligence based protective relay data acquisition system to correct current transformers and capacitive voltage transformers secondary waveform distortions. The protective relay data acquisition system receives voltage and current signals from current transformers and capacitive voltage transformers and prepares the inputs to the main board after some pre-processing. Current transformers and capacitive voltage transformers provide instrument level current and voltage signals to meters and protective relays in high voltage and extra high voltage systems. The accuracy and performance of protective relays in high voltage and extra high voltage systems are directly related to steady state and transient performance of current transformers and capacitive voltage transformers. Current transformers saturation and capacitive voltage transformers transient could lead to protective relay mal-operation or even prevent tripping. The key of the proposed scheme is to use artificial neural network to achieve the inverse transfer functions of current transformers and capacitive voltage transformers. Simulation studies are preformed and the impacts of changing different parameters are studied. Performance study results show that the proposed scheme is accurate and reliable. The proposed algorithm has also been implemented and tested on a digital signal processor board. Details of the implementation and experimental studies are provided in the paper.     

变压器绕组微小变形脉冲响应检测系统的设计

频率响应法( FRA)广泛应用于变压器绕组变形的检测.针对传统的扫频方式检测频带窄,灵敏度低且测试速度慢的缺点,本文设计了一套基于纳秒脉冲响应法的变压器绕组微小变形检测系统.系统的硬件部分由纳秒脉冲源、高速采集模块、阻抗匹配器和计算机构成.其中纳秒脉冲源可产生上升沿5ns、半脉宽50ns、幅值2kV的双指数脉冲.采用L...