Study on diagnosis of power transformer winding deformation through vibration signal
06 Jul 2016-pp 654-658
TL;DR: In this paper, the authors used the mechanism of transformer vibration and Fourier transform to determine the mechanical condition of a power transformer in a single-phase to three-phase case.
Abstract: As one of the most important equipment in power system, power transformer plays a major role in guarantying the safe and stable operation of power system. Among the faults in transformer, winding deformation takes a large part. Since 1970s, lots of method, such as Frequency Response Analysis, Low Voltage Impulse have been put into winding deformation detection. Among these methods, Vibration Analysis from oil tank has gained much attention through its advantage that it is closely related with the mechanical condition of winding and core and can be used in on-line monitoring. This paper based on the mechanism of transformer vibration and Fourier Transform, choose Fundamental Frequency of Vibration (FFV), Maximum Amplitude in Frequency spectrum (MAF) and Transformer Vibration Entropy (TVE) as vibration eigenvalue to indicate the mechanical condition of transformer. What's more, the failure threshold for diagnosis is acquired through 78 power transformer varying from 110kV to 750kV, single phase to three phase. Among the test results, the vibration eigenvalue from one 110kV power transformer who suffered an external short-circuit accident shows that the winding of 3 phases all have winding deformation. The conclusion and diagnosis results are proved to be effective after the transformer is sent back to the manufacturer and make a pendant-core examination. The diagnosis method for power transformer in this paper based on tank vibration can make contributions to condition monitoring.
Citations
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TL;DR: In this paper , one kind of magnetic compensation method is adopted to suppress the dc bias, and the core vibration caused by the transformer magnetic state change is studied in detail, which could provide a basic method for reducing vibration.
Abstract: The variation of magnetic state of transformer often causes the violent vibration of the transformer various parts, especially the core. The most obvious magnetic state change of the transformer is usually caused by the dc component. In this article, one kind of magnetic compensation method is adopted to suppress the dc bias, and the core vibration caused by the transformer magnetic state change is studied in detail. At first, on the basis of measuring the magnetostriction and calculating the vibration displacement of transformer core, the research on the vibration increment created by the dc bias is carried out. Second, the transformer core vibration before and after the dc bias suppression is simulated, and the difference of the transformer with a magnetic compensation capacity is analyzed. Finally, based on the VIBXPERT1II FFT data acquisition and signal analyzer, the vibration of measuring points under the different magnetic state and the different measuring point under the same magnetic state are collected. The vibration tendency of each measuring point is given with the variation of the magnetic state. Thus, the vulnerable spot of the core vibration and the basic law of the transformer vibration are obtained, which could provide a basic method for the reducing vibration.1Registered Trademark.
5 citations
01 Sep 2018
TL;DR: Time-frequency vibration analysis of transformer tank vibration characteristics can be used to monitor winding condition and diagnose winding fault and validate the correctness of Hilbert spectrum analysis of transient vibration response.
Abstract: Huge electromagnetic force during sudden short circuit can cause severe winding mechanical fault. Transformer tank vibration characteristics are closely related to winding mechanical condition. Transient vibration response on transformer tank under short circuit impact can be utilized to monitor winding condition and diagnose winding fault. Short circuit impact experiment according to IEC standard is performed on a 110kV transformer. 33 times impacts were performed at A-phase and tank vibration signal is recorded every time during the impact. Since transformer transient vibration signal is non-linear and non-stationary, this paper utilizes Hilbert-Huang Transform (HHT) methodology to analyze transformer vibration signal in time-frequency domain. 200Hz-1000Hz component in Hilbert spectrum is deeply studied. Image processing method is used to quantity the occurrence number of frequency above 200Hz in Hilbert spectrum. The result shows 800Hz-1000Hz component increases largely during 23rd impact compared with the previous impact result. Thus, 800Hz-1000Hz component in Hilbert spectrum can be regarded as an indicator to diagnose winding fault. What's more, Short Circuit Impedance (SCI) experiment shows that SCI variation rate of A-phase changes 1 % after 24th impact and increases to −21.85% after 33rd impact. Suspended core experiment after the short circuit impact experiment reveals that severe winding mechanical fault occurs in both high voltage winding and medium voltage winding. Both of the results validate the correctness of Hilbert spectrum analysis of transient vibration response. Therefore, time-frequency vibration analysis can be used to monitor winding condition and diagnose winding fault.
4 citations
Cites background from "Study on diagnosis of power transfo..."
...Power transformer will suffer short circuit impact inevitably during on-site operation, which may cause winding mechanical fault and even winding insulation failure[2]....
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01 Oct 2018
TL;DR: A model created in COMSOL and Matlab software and a case study for a segment of windings displays the acquired results.
Abstract: Power transformers are vital components of the power system. These electrical devices can experience multiple types of faults within them. Mechanical defects are relatively difficult to detect since they occur inside the structure of the power transformer. Magnetostriction can create this type of faults in magnetic core and electrodynamic forces can cause them in windings. Diagnostic methods mainly use vibration information from the surface of transformer. This is an indirect approach and causes additional errors since vibrations need to propagate transformer structure before sensors receive them. However, it is possible to calculate the mechanical situation in windings by modelling this part of the transformer as a mass and spring system with forces acting upon it and applying dynamic genetic algorithm. This paper describes a model created in COMSOL and Matlab software and a case study for a segment of windings displays the acquired results.
4 citations
Cites methods from "Study on diagnosis of power transfo..."
...There are many methods for measuring vibrations on transformer tank surface [1], [2], [3]....
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01 Jun 2018
TL;DR: In this paper, a single winding was used to perform electrically excited vibration frequency response experimentation whose platform mainly consisted of a harmonic source and its control system, and the result showed that winding VFRFs are similar under various amplitude of excitation current which verifies the winding structure can approximately be regarded as linear system.
Abstract: Transformer winding vibration frequency response characteristics is the direct reflection of winding mechanical condition. Studying transformer winding vibration frequency response characteristics is very meaningful for winding modal analysis and can be utilized for winding mechanical fault diagnosis. This paper uses a single winding to perform electrically excited vibration frequency response experimentation whose platform mainly consists of a harmonic source and its control system. The electrical excitation is a constant current whose frequency sweeps from 50Hz to 500Hz. Winding axial vibration response of different discs are measured. Furthermore, in order to study the influence of various clamping pressures on winding vibration frequency response, a special device is designed to change and measure the clamping pressure on the winding. Vibration Frequency Response Function (VFRF) is used to reflect winding vibration frequency response characteristics. The result shows that winding VFRFs are similar under various amplitude of excitation current which verifies the winding structure can approximately be regarded as linear system. The variation tendency of natural frequency is difficult to abstract from the VFRF due to too many modal numbers. Winding VFRFs under various clamping pressures are different and Coefficient Correlation (CC) is brought up to evaluate the variation. CC decreases with the clamping pressure variation increasing and measure location has a large influence on the sensitivity of CC when it is used as an indicator to evaluate the change of winding pressure clamping. Studying electrically excited winding vibration frequency response under different clamping pressures is meaningful in winding looseness diagnosis.
2 citations
Cites background from "Study on diagnosis of power transfo..."
...Power transformer is one of the most crucial equipment in power system [1]....
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01 Aug 2018
TL;DR: In this paper, the authors used piezoelectric accelerometer sensors to detect vibrations in a 20kV distribution transformer tank, which has a reading accuracy of 5 × 10-5 m/s? in positive or negative acceleration.
Abstract: The distribution transformer is an important tool in the power system. During operation, the transformer produces vibrations indicated on its performance. Transformer monitoring based on the condition of the transformer becomes very important due to mechanical failure resulting in different vibration patterns caused by winding, cores or both. Differences in the design and placement of sensors used can give different vibration measurement results on the transformer. This research designs piezoelectric accelerometer sensors to detect vibrations in a 20kV distribution transformer tank. The results show that the piezoelectric accelerometer sensor design has a reading accuracy of 5 × 10–5 m/s? in positive or negative acceleration, with the measuring instrument of vibration meter Lutron VB-8200 and proves that the main source of vibration caused by winding and cores located 2/3 from the bottom to the middle on the measurement of vibration on the secondary side of the transformer tank.
1 citations
References
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TL;DR: In this article, a model developed for a transformer monitoring system to estimate transformer tank vibration is presented, which takes into account the main physical phenomena generating vibrations in the different transformer elements and how these vibrations are superposed and transmitted to the tank.
Abstract: In this paper, a model developed for a transformer monitoring system to estimate transformer tank vibration is presented. The model calculates vibration on the transformer tank starting from some input variables that can be easily measured on the transformer. Tank vibration is also measured, showing a good concordance between estimated and measured values if the transformer is healthy. In case of a winding deformation winding vibration and, consequently, that of the tank, changes and a big difference between estimated and measured vibration appear. To estimate tank vibration, the model takes into account the main physical phenomena generating vibrations in the different transformer elements and how these vibrations are superposed and transmitted to the tank. The model has been tested experimentally on a test transformer fitted with internal and external accelerometers. A deformation has been provoked in the test transformer winding with the aim of testing the model's ability to detect it. The model has been also tested on several in-service grid transformers. The results of the experimental validation are shown in Part II of the paper.
244 citations
"Study on diagnosis of power transfo..." refers methods in this paper
...Lots of work have been done in paper through the following parts: firstly, using signal processing method such as Hilbert-HuangTransform[9] and Wavelet Transform[10] to detect winding faults; secondly, studying on the mechanism and influencing factors on vibration using Finite Element Method (FEM) and experiment[11-17]; thirdly, dynamic response of winding vibration under short circuit[17]....
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TL;DR: In this article, a tank vibration model was proposed as a method to detect the winding deformation in power transformers, which was validated in a 1500-kVA experimental transformer constructed as a reduced scale model of a 60-MVA 220-kV unit.
Abstract: In Part I of the paper, a tank vibration model was proposed as a method to detect the winding deformations in power transformers. This model is incorporated in a model-based monitoring system for power transformers. In this paper, the experimental verification of the proposed model that calculates vibration on the transformer tank is reported. The model was validated in a 1500-kVA experimental transformer constructed as a reduced scale model of a 60-MVA 220-kV unit. In order to load the test transformer, the opposition method described in IEC 60076-2 Standard was used allowing to vary the load and power factor over a wide range. Sensors to measure vibrations and temperature were installed in the test transformer. The model was validated under different test transformer operating conditions. In order to verify the model's ability to detect failures, a deformation was provoked in the test transformer winding. Model predictions were compared with the measured vibration in that situation. The model has also been applied to four (30-40 MVA) grid transformers. Some results of this field validation are presented in this paper.
164 citations
"Study on diagnosis of power transfo..." refers methods in this paper
...Lots of work have been done in paper through the following parts: firstly, using signal processing method such as Hilbert-HuangTransform[9] and Wavelet Transform[10] to detect winding faults; secondly, studying on the mechanism and influencing factors on vibration using Finite Element Method (FEM) and experiment[11-17]; thirdly, dynamic response of winding vibration under short circuit[17]....
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TL;DR: In this paper, power transformers are considered to be the heart of the transmission and distribution sectors of electric power systems; monitoring their condition and diagnosing faults are important parts of the maintenance function.
Abstract: Power transformers are in service under different environmental, electrical, and mechanical conditions [1] and may be subject to enormous hazards during the course of operation [2], [3]. They are commonly considered to be the heart of the transmission and distribution sectors of electric power systems; monitoring their condition and diagnosing faults are important parts of the maintenance function [4]. Utility engineers strive to keep power transformers in service and to prevent even shortterm outages. Failure of a transformer can cause extensive damage to equipment owned by consumers or the utility [5].
144 citations
"Study on diagnosis of power transfo..." refers background in this paper
...Since 1970s, lots of effort have been put into the study on winding deformation detection [3-6]....
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TL;DR: In this article, a new technique based on vibration measurement to diagnose power transformers, called the onload current method (OLCM), is presented, which can acquire the fundamental frequency component of the core vibration signal without running the transformer at the open-circuit condition.
Abstract: This paper presents a new technique based on vibration measurement to diagnose power transformers, which is called the onload current method (OLCM). It can acquire the fundamental frequency component of the core vibration signal without running the transformer at the open-circuit condition. The diagnostic method adopted and the experimental test results are reported. Tests have been performed at normal operating conditions in both the manufactory and the laboratory. With the tests performed in the manufactory, the vibration characteristics of transformer windings and core are described, and then the principle of OLCM is introduced. To verify the validity of OLCM, the laboratory tests are conducted which relates the transformer vibrations to the simulative fault. But the presented method was verified on a 5-kVA transformer which is a very far cry from an actual power transformer. It needs to be developed further before OLCM can be used effectively on the transformer in the field
115 citations
"Study on diagnosis of power transfo..." refers background in this paper
...What’s more, the fundamental frequency of core vibration is twice its source frequency and its value is basically proportional to the voltage square[19]....
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TL;DR: In this article, a wind condition assessment model using vibration signals is presented, which can be used to diagnose power transformers online, based on the correlation analysis of wind vibrations, and a health parameter is proposed via principal component analysis.
Abstract: 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.
81 citations
"Study on diagnosis of power transfo..." refers methods in this paper
...Lots of work have been done in paper through the following parts: firstly, using signal processing method such as Hilbert-HuangTransform[9] and Wavelet Transform[10] to detect winding faults; secondly, studying on the mechanism and influencing factors on vibration using Finite Element Method (FEM) and experiment[11-17]; thirdly, dynamic response of winding vibration under short circuit[17]....
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