Winding Vibration Research Articles

Comprehensive vibration generation model of transformer winding under load current

This study proposes a comprehensive model to investigate winding vibration characteristics. The radial vibration model is firstly established based on the Euler–Bernoulli beam theory, and the radial acceleration is found to be the second derivative of deflection under the quasi-static load. The fluid-loading effect of oil on winding vibration is then investigated through experimental modal analysis and finite element method. This effect leads to the decrease of natural frequencies and the increase of damping ratios. The harmonic response of axial winding vibration at 100 Hz shows the symmetry distribution that vibration on the one quarter and three-quarters of the winding height are larger than other positions. The radial acceleration is not affected by the clamping pressure, whereas the axial acceleration is in a reciprocal relationship with it.

A Variational Mode Decomposition Approach for Degradation Assessment of Power Transformer Windings

Windings are the most critical components in power transformers, and the related mechanical degradation assessment has attracted an increasing attention in recent years. In this paper, a novel feature extraction method based on an amalgamation of variational mode decomposition (VMD) and wavelet transform (WT) is encouraged, which correlates the nonlinear structural parameters of windings with the mechanical degradation. First, the winding vibration mechanism is explored, and the relationship between the transient vibration of windings and the structural parameters is studied. Next, the vibrations are decomposed into multiple modes using VMD, and the feature vector is extracted from the modes by means of WT. After that, three classification algorithms are employed, including support vector machine, naive Bayes classifier, and artificial neural network. In the experiment, the winding structure degradation was simulated via adjusting the clamping force. The vibrations from three winding units are used to train and test the classifiers, and their performance is evaluated and compared. The results demonstrate that the proposed feature extraction method with an appropriate classifier is effective for winding degradation assessment.

Investigation on vibration source and transmission characteristics in power transformers

The tank vibration of power transformers comes from alternating forces acting on the core and windings. It is meaningful to study the vibration sources and the transmission characteristics in transformers for interpreting the constitution of the tank vibration specifically. This paper experimentally investigates the coupling between the winding vibration and the core vibration, as well as the vibration transmission characteristics on a single phase power transformer the winding vibration coupled with the core vibration has a broader frequency band than the responses caused by the electromagnetic force. For transmission characteristics, the oil-borne transmission is the main path for the winding vibration, while the structure-borne transmission highly depends on the modal characteristics of the tank. This work improves the understanding of the relationship between the internal vibrations and the tank responses.

Vibration of circular rings coupled by elastic elements

The three-dimensional vibration of circular rings coupled by elastic elements is investigated in this paper. The vibration characteristics of a single circular ring are examined first analytically and experimentally and then used as building blocks for a stack of concentric rings connected by elastic insulators, which is used as an approximate-model of a disk-type transformer winding. The key outcomes of this research are a more realistic model for transformer winding vibration and determining its three-dimensional vibration characteristics. The model is also verified experimentally. An experimental-based numerical method is also developed for identifying the stiffness and damping properties of the elastic elements.

Effect of No-load and Load Condition on Transformer Sound

Increasing environment noise pollution is a matter of great concern and of late has been attracting public attention. Sound produces the minute oscillatory changes in air pressure and is audible to the human ear when in the frequency range of 20Hz to 20 kHz. The chief sources of audible sound are the magnetic circuit of transformer which produces sound due to magnetostriction phenomenon, vibration of windings, tank and other structural parts, and the noise produced by cooling equipments. This paper presents the validation for sound level measurement scale, why A-weighted scale is accepted for sound level measurement, experimental study carried out on 10MVA Power Transformer. Also presents the outcomes of comparison between No-Load sound & Load sound level measurement, experimental study carried out on different transformer like - 10MVA, 50MVA, 100MVA Power Transformer, to define the dominant factor of transformer sound generation.

Analysis of Winding Vibration Characteristics of Power Transformers Based on the Finite-Element Method

The winding is the core component of a transformer, and the technology used to diagnose its current state directly affects the operation and maintenance of the transformer. The mechanical vibration characteristics of a dry-type transformer winding are studied in this paper. A short-circuit test was performed on an SCB10-1000/10 dry-type transformer, and the vibration signal at the surface was measured. Based on actual experimental conditions, a vibration-simulation model of the transformer was established using COMSOL Multiphysics software. A multiphysics coupling simulation of the circuit, magnetic field, and solid mechanics of the transformer was performed on this model. The simulation results were compared with measured data to verify the validity of the simulation model. The simulation model for a transformer operating under normal conditions was then used to develop simulation models of transformer-winding looseness, winding deformation, and winding-insulation failure, and the winding fault vibration characteristics were analyzed. The results provide a basis for detecting and analyzing the mechanical state of transformer windings.

An On-line Feature Extraction Method for Transformer Vibration Signals

FFT or wavelet transform method is usually used in transformer on-line vibration signal analysis apparatus. In order to extract features of transformer vibration signals reliably and accurately, a method which is based on FFT and wavelet packet transform was proposed for type identification of transformer vibration signals using k-nearest neighbor (KNN). First of all, the known transformer vibration signals were decomposed by FFT and several characteristic bands which were used to determine the layer number of wavelet packet decomposition were extracted; secondly, the feature vectors contained energy entropy of a selective wavelet packet decomposition for characteristic bands was obtained; Finally, KNN classifiers are utilized for pattern recognition. Five kinds of winding and core state vibration signals under conditions of transformer short-circuit test in the laboratory were extracted and recognized using the above methods. Simulation results demonstrate that the method proposed can extract the features of transformer vibration signals accurately and reliably, providing a good reference for the recognition of partial discharge signals.

Electromagnetic vibration of controllable saturable reactor under different DC control current

Controllable saturable reactor (CSR) has been developed rapidly because of its continuous adjustable output characteristics. However, the vibration of the saturated core is serious and becomes a bottleneck problem in its application. Electromagnetic vibration analysis become an essential part in de signing and manufacturing. In this paper, the electromagnetic vibration of cores and windings of CSR under actual working conditions was numerical calculated and measured. In order to obtain the magnetic properties, magnetization curves under DC bias were got through repeated measuring with different setting and simple calculation. Magnetostriction (MS) was measured by laser interferometer under DC bias. Based on the measured properties under different DC control current, magnetic field was firstly analyzed and the magnetic forces, which include Lorentz, Maxwell and magnetostrictive force, were calculated. Then the vibration of cores and windings due to electromagnetic forces were calculated by using a weak 3D magneto-elastic model under actual working conditions. Finally, the vibration of a CSR, which is a single-phase prototype with 4.4 kVar/220 V, were tested and analyzed. The error between measurement and calculation results is in a reasonable range.

Transformer winding fault detection by vibration analysis methods

In this paper, the vibration of power transformer windings is studied with the aim of identifying the winding structural condition. A winding vibration model coupled with electromagnetic force analysis is proposed to obtain the steady-state vibration distribution along the axial direction. During the experiment, the model was validated on a full size, 50MVA, three phase power transformer. Good agreement was found between the measured vibrations and the vibrations that were calculated from the model developed in this study for a healthy winding. The effect of the winding clamping force on vibration is studied to assess the winding clamping state, and different types of winding deformations were simulated to extract diagnostic information. The preliminary study shows that it is feasible to predict the mechanical faults of transformer windings with the vibration method.

变压器绕组振动特性研究

在理论分析影响变压器绕组振动各因素的基础上，利用ANSYS建立变压器有限元模型仿真分析，验证了不同的预紧力大小对绕组振动固有频率的影响。利用变压器振动在线监测系统，对变压器油箱表面测得的振动信号进行了研究，实验验证了变压器绕组振动主要集中在基频100 Hz处，且基频幅值与负载电流的平方满足正比例关系。 On the basis of theoretical analysis of various factors affecting the vibration of transformer windings, the finite element model simulation analysis of the transformer was built by ANSYS. The effect of different precompression on the natural frequency of winding vibration was verified. The vibration signal of the transformer tank surface was studied by the on-line monitoring system of the transformer vibration. The experimental results showed that the vibration of the transformer windings was concentrated in the fundamental frequency 100 Hz. The amplitude of the fundamental frequency was proportional to the square of load current.

Winding Condition Assessment of Power Transformers Based on Vibration Correlation

In this paper, a winding condition assessment model using vibration signals is presented, which can be used to diagnose power transformers online. The basic principle of this model is based on the correlation analysis of winding vibrations. In the model, the fundamental frequency vibration analysis is used to separate the winding vibration from the mixed signal. Then, a health parameter is proposed via principal component analysis. Another parameter is also proposed to detect the fault locations for suspected faulty transformers. In laboratory tests, the model is validated on a specifically designed 110-kV transformer. During the tests, man-made winding deformations are simulated to compare the vibrations under different conditions. The model has also been tested on several in-service power transformers. The preliminary study shows that the proposed model is feasible to assess the power transformer winding condition.

Research on the Vibration Condition On-Line Monitoring System for EHV Power Transformer

The paper introduces a design scheme for the Extra High Voltage (EHV) transformer condition on-line monitoring system, which is based on the collection and analysis of the transformer winding and core vibration signals. This system is composed of vibration acceleration signal sensors and the signal analyzing computer where the collected vibration signal is saved and processed. The analyzing computer can accomplish the missions of data acquisition control, data analysis and the historical data query. Vibration characteristic values of transformer winding and core include peak to peak value, spectrum, kurtosis, and the amplitude 100Hz component and its higher harmonic components. They are extracted, and the characteristic trend curves are drawn by data analysis, so that EHV transformer on-line monitoring and fault diagnosis are accomplished.

Multi-field Coupling Simulation and Experimental Study on Transformer Vibration Caused by DC Bias

DC bias will cause abnormal vibration of transformers. Aiming at such a problem, transformer vibration affected by DC bias has been studied combined with transformer core and winding vibration mechanism use multi-physical field simulation software COMSOL in this paper. Furthermore the coupling model of electromagnetic-structural force field has been established, and the variation pattern of inner flux density, distribution of mechanical stress, tension and displacement were analyzed based on the coupling model. Finally, an experiment platform has been built up which was employed to verify the correctness of model.

An experimental study of winding vibration of a single-phase power transformer using a laser Doppler vibrometer

Transformer tank vibration has been used for the condition monitoring and fault diagnosis of power transformers, as well as for the evaluation of radiated sound power from such power transformers. In both applications, seeking a correlation between transformer tank vibration and the vibration of the transformer windings and core becomes a challenge for fault identification and noise control at the sources of vibration and noise. The purpose of this paper is to experimentally investigate the winding vibration of an electrically live power transformer and characterize the changes in the spatial and frequency features of the vibration as various mechanical faults are introduced to the transformer winding. To avoid the effects of transducer loading and electromagnetic fields on the measurement results, a laser Doppler vibrometer was used to make non-contact measurements of the winding vibration.

Compression behaviors of oil-immersed insulating pressed-boards made of Kraft Pulp

We report on compression behaviors of oil-immersed insulating pressed-boards used in transformers for analyzing the axial vibration of windings. Compression behaviors of oil-immersed pressed-boards depended on strain rates and temperatures, that is, viscoelastic behaviors were observed. By applying the time-temperature superposition principle to the pressed-boards? compression behaviors, we obtained the relationship between the modulus of compressive elasticity and strain rate. Based on the relationship, the pressed-boards? compression behaviors were estimated under the condition of high compression forces and high strain rates. The 20cSt silicone liquidimmersed pressed-boards showed almost the same compression behavior as the mineral oil immersed pressed-boards. The viscoelastic behavior of the oil-immersed pressed-boards was mainly decided by the properties of the cellulose fibers, and not influenced by the viscosity of the immersed oils.

Faults Diagnosis of Converter Transformer Based on the Vibration Method

The vibration of windings and iron core causes the overall vibration of the transformer. Significant changes of transformer vibration condition will take place when the windings or core has fault, so the vibration method can be used to diagnose the transformer's potential fault. The characteristics and transmission route of the transformers' vibration were analyzed. The vibration of a certain transformer in converter station was picked up, using vibration measuring system. The test results aree analyzed comparatively and maintenance suggestion was proposed.

Research on the Application of Transformer Vibration Model in the Detection of Turn-to-Turn Short-Circuit Fault

The magnitude of transformer vibration is influenced by that of voltage and current, which might lead to the wrong results in detecting the fault of core and winding by vibration analysis method. Based on the generation machnism of vibration signal, a transformer tank model was presented in this paper. It concerned about the relationship between the vibration (core vibration and winding vibration) and the operating parameter (voltage and current). The experiments were conducted in lab under different voltage and current, and then the vibration model was set up. Furthermore, this vibration model was also used to detect the simulated turn-to-turn short-circuit fault on windings. By comparing the vibration magnitude calculated by the model with the measured one, the defect condition of transformer was confirmed, which verifies that the vibration model presented in paper is effective.

502 油入り変圧器のコイルとタンクの流体-構造連成解析

Due to increase of capacity and weight saving, bigger electrostatic and magnetic energy is stored in transformer, compared with conventional transformer. Because of these, Vibration and noise are likely produced. In the field of noise reduction of transformer, core vibration by magnetic-striction, winding vibration and sound proof of transformer and tank have been studied. Winding vibration due to the currents produce sound wave in the insulation oil. This wave spreads in the oil and vibrates tank of transformer. The transformer tank yields a fluid elastic vibration hitherto, two-dimensional fluid is analyzed by FEM with dis placement method. However, the fluid-structural analysis of a coil and a tank of transformer have not been studied by a three-dimensional FEM. In this paper, the method of calculating the character frequency which took the influence of oil into consideration from the fluid-structural analysis by three-dimensional FEM which is not in the former with sufficient accuracy was found out. Since it showed clearly that it changes with modes of vibration, the decreasing rate of character frequency and oscillating attenuation by oil are reported.

Electromagnetic Vibration Analysis of the Winding of a New HVDC Converter Transformer

HVDC converter transformers suffer from serious noise pollution caused by the electromagnetic vibration of their windings and cores, since the nonlinear behavior of converters produces a large number of harmonic currents. This paper presents an electromagnetic vibration analysis of a new autoinductive harmonic suppression (AIHS) converter transformer's windings, taking harmonic currents into consideration. The currents of the windings are computed by using the multiwinding transformer theory. Then, the electromagnetic forces in the radial and axial direction of three windings are calculated by using Lagrange's theorem. Three windings and the corresponding core of the AIHS converter transformer are constructed and simulated by a 3-D finite-element method model. The transient dynamic (time-domain) simulation results reveal that the AIHS converter transformer and its corresponding inductive filters can suppress the electromagnetic vibration of windings.

Laboratory Studies of a New Stator Slot Wedge Tester for HV Generators

Stator winding vibration is the most common cause of unexpected failure of high-voltage (HV) generators. Stator bars are generally fixed in slots by using slot wedges and a side packing system. Loose slot wedges could result in excessive vibration of the stator bars, which would accelerate the deterioration of the ground wall insulation. Loose slot wedge testing is consequently one of the most important general examination procedures to make sure the condition of HV generators. The common method used for slot wedge testing is manual measurement, whereby the slot wedge is tapped by hand using a small hammer. A judgment on looseness is made based on the sound from it. A digital signal processor (DSP)-based loose slot wedge tester is described in detail in this paper, including both hardware and software design. It was developed in our laboratory based on the study of slot wedge vibration characteristics in its loosening process. Since embedded software system of the DSP is oriented to a specific industrial field while PC system is of a general purpose, the device has many advantages compared to traditional manual measurement or other slot wedge testing equipment, such as portability, high intelligence, low power consumption, etc. The tester was applied for laboratory loose slot wedge testing of a slot model. The test results soundly verified the good performance of the device.