Winding Deformation Detection Research Articles

An Insulation Monitoring Method for Transformer Windings Based on Electroluminescence Effect

Currently, the insulation monitoring method for transformer windings mainly monitors voltage, current, leakage inductance, leakage magnetic field, temperature, and dissolved gas in oil. However, these methods often have the disadvantages of low sensitivity, inability to locate, and slow response time. This paper presents a novel insulation monitoring method for transformer windings based on electroluminescence. In this method, electroluminescent coatings are sprayed on the sides of the blocks between pancake windings. The electric field intensity between the windings is measured according to the coating’ luminance, then the winding insulation state is monitored, and faults can be located. To verify this method, we make a transformer winding model based on the principle of capacitive voltage division. Interturn and interlayer insulation faults are simulated by changing capacitors. The results show that the method has an error of less than 3% in measuring the electric field between transformer pancake windings and is feasible for transformer winding insulation monitoring. In addition, this method also can be used for the detection of transformer winding deformation.

Study on Vibration Characteristics of Transformer Winding

Compared with the existing winding deformation detection technologies, such as the frequency response method and short-circuit reactance, the vibration analysis method can effectively detect the loose state of windings. This paper has carried out mechanism analysis and experimental study on the change of winding modal characteristics caused by two kinds of defects, analyzed the transmission characteristics of three-phase double winding transformer winding vibration in the transformer oil and structure, studied the influence of pad falling off, plastic deformation and other defects on the mechanical state of the winding, calculated the winding short-circuit vibration signals corresponding to different mechanical states, and extracted the vibration characteristics that can effectively reflect the mechanical state of the winding. The research conclusion can provide an important basis for transformer fault diagnosis.

Remote online monitoring system for transformer winding deformation based on current–voltage characterized graph

Transformer winding deformation threatens the power system’s safe and stable operation, and early detection of transformer winding deformation can reduce economic losses. This work analyzed the basic principle of the transformer winding deformation online method based on the current–voltage characterized graph. The simulation model was established and the frequency of the identification signal was changed to study the influence of the signal frequency on the change rate of the parameters of the characteristic graph. Combined with cloud technology, a remote online monitoring system for transformer winding deformation based on a current–voltage characterized graph was developed and experiments were carried out. The results showed that the deformation of the transformer winding affected the change of its impedance, thus causing the change of the parameters of characterized graph. The impedance of the transformer was mainly composed of its reactance, and the signal frequency has no significant effect on the rate of change of the parameters of characterized graph. The developed system can monitor the health status of transformer winding. This work can provide a scientific basis and experimental basis for early detection and early warning of transformer winding deformation.

Response Test of Power Transformer Windings Excited by Nanosecond Pulse

At present, the detection of transformer winding deformation in the offlinephase, in order to discover the small transformer winding deformation, real-ize the online monitoring, in this paper, using nanosecond pulse frequencyresponse analysis method, the detection of transformer winding deformationis studied, the results show that the nanosecond pulse frequency responseanalysis method in the detection of transformer winding deformation withhigh reliability and sensitivity.In order to verify the repeatability of themethod, the method was used again at a 30-day interval under the conditionthat the detection environment was basically unchanged. The ρ value was0.9719 in the range of 1 kHz∼1 MHz.

Research Situation Analysis of On-line Detection Technology for Power Transformer Winding Deformation

Background: Winding deformation is one of the most common faults in power transformers, which seriously threatens the safe operation of transformers. In order to discover the hidden trouble of transformer in time, it is of great significance to actively carry out the research of transformer winding deformation detection technology. Methods: In this paper, several methods of winding deformation detection with on-line detection prospects are summarized. The principles and characteristics of each method are analyzed, and the advantages and disadvantages of each method as well as the future research directions are expounded. Finally, aiming at the existing problems, the development direction of detection method for winding deformation in the future is prospected. Results: The on-line frequency response analysis method is still immature, and the vibration detection method is still in the theoretical research stage. Conclusion: The ΔV − I1 locus method provides a new direction for on-line detection of transformer winding deformation faults, which has certain application prospects and practical engineering value.

Transformer Winding Deformation Detection Based on BOTDR and ROTDR.

In order to realize distributed measurement of transformer winding temperature and deformation, a transformer winding modification scheme with a built-in distributed optical fiber was designed. By laying a single-mode fiber and a multi-mode fiber on the transformer winding, the Brillouin optical time domain reflection technique (BOTDR) and the Raman optical time domain reflection technique (ROTDR) are used to measure the strain and temperature of the winding to complete the more accurate winding deformation detection. The accuracy of strain and temperature sensing of this scheme was verified by simulation. Then, according to the scheme, a winding model was actually wound, and the deformation and temperature rise tests were carried out. The test results show that this scheme can not only realize the deformation detection and positioning of the winding, but can also realize the measurement of the winding temperature; the temperature measurement accuracy reached ±0.5 °C, the strain measurement accuracy was 200 με, and spatial resolution was up to 5 m. In this experiment, the deformation location with the precision of 2 turns was realized on the experimental winding.

Simultaneous radial deformation and partial discharge detection of high‐voltage winding of power transformer

Condition monitoring of power transformers has attracted a lot of attention due to their important roles in determining power system reliability. Radial deformation of power transformer winding should be monitored online to prevent more damages to winding and possible transformer outage. The ultra-high-frequency (UHF) stepped-frequency synthetic-aperture radar imaging method has recently been proposed as an online method for high-voltage winding radial deformation detection. On the other hand, partial discharge (PD) as another defect of the transformer winding propagates UHF signals in the transformer environment, which should be detected online. In this study, the practical application of a designed monitoring system is investigated for simultaneous online detection of both PD and radial deformation defects in a real three-phase power transformer. In addition, radial deformation is localised through a monitoring system designed based on the proposed method. Using this system, only one set of antennas is needed to detect both defects which lead to reducing the number of installed antennas and economic application of the monitoring system.

Research on Winding Deformation Detection and Diagnosis Technology of Power Transformer

With the continuous increase of power grid capacity, transformer damage accidents caused by short-circuit faults are on the rise. Timely and effective measurement of transformer winding deformation can effectively prevent further deterioration of transformer deformation and ensure that transformer does not occur accidents. This paper summarizes the methods, principles, influencing factors and judging criteria of winding deformation detection, and summarizes the important research results in the field of transformer winding deformation in recent years. Finally, this paper compares different detection methods from the aspects of detection methods, influencing factors of test results, detection information, detection sensitivity, deformation judgment methods and detection standards.

Detection of HV Winding Radial Deformation and PD in Power Transformer Using Stepped-Frequency Hyperboloid Method

Detection of winding deformation and partial discharge (PD) is essential for monitoring and failure risk assessment of power transformers. Recently, an online method based on electromagnetic waves has been proposed for detecting radial deformation (RD) in high-voltage (HV) transformer winding using ultra wide band pulses, called the hyperboloid method. In this method, a short pulse is transmitted toward HV winding and its reflection captured using a set of antennas. By comparing and analyzing signals in sound and deformed conditions, the RD can be detected. On the other hand, signals radiated from PD defect in transformers are generally appeared in the range of UHF band (0.3–3-GHz frequencies). In this paper, the hyperboloid method is proposed for implementation in UHF band, and the PD effect on the result of the hyperboloid method is investigated. Thus, a set of UHF sensors can be used for the detection of PD and detection and localization of RD defect. Results show that PD signals can affect the signal of the hyperboloid method and lead to wrong localization of RD. In order to solve this problem, the UHF stepped-frequency method is proposed, utilized, and tested on the HV winding of a 1.6-mega volt ampere (MVA) distribution transformer. Experimental results show the capability of the proposed method for detecting both defects using only one set of UHF antennas.

Fault Identification for Transformer Axial Winding Displacement Using Nanosecond IFRA and SFRA Experiments

Nanosecond IFRA has the potential to realize online detection of power transformer winding deformation and displacement. But this method is not mature even in offline condition, and the reliability, accuracy and repeat ability of which are in doubt. To verify the reliability and accuracy of nanosecond IFRA a comparison experiment is conducted between it and a mature method which is applied widely all over the world, SFRA. In this experiment, three levels of axial displacements are experimentally simulated on a dry-type distribution transformer in the lab and both a nanosecond IFRA system and a commercial SFRA analyser are applied to obtain the frequency responses at each fault level separately. To verify the repeatability of Nanosecond IFRA, two Nanosecond IFRA measurements conducted in a time interval of 30 days with all the test condition remaining the same are compared. The results are analysed by visual inspection and quantitative comparison.

A New Multi-Conductor Transmission Line Model of Transformer Winding for Frequency Response Analysis Considering the Frequency-Dependent Property of the Lamination Core

Multi-conductor transmission line (MTL) model of power transformer winding for frequency response analysis (FRA) has been successfully applied for the purpose of studying the characteristics of winding deformations. Most of the time it is considered that, at a frequency above 10 kHz, the flux does not penetrate the core, and the iron core losses due to hysteresis and eddy current can be neglected accordingly. However, in fact, there is still a little flux residing in the core, and it has a significant influence on inductances and resistances of transformer winding even up to approximately 1 MHz. In this paper, by introducing the anisotropic complex permeability of the lamination core into calculating inductances and resistances of the MTL model, a new MTL model considering the frequency-dependent property of the lamination core for FRA is presented. In addition, the accuracy and effectiveness of the MTL model are validated by means of a comparison between measured and emulated FRA results in a wide frequency range from 10 Hz up to 10 MHz. This precise MTL model of the transformer winding provides us a more objective and positive condition for simulation research of winding deformation detection.

A New Interpretation of FRA Results by Sensitivity Analysis Method of Two FRA Measurement Connection Ways

As a reliable and non-destructive technique, frequency response analysis (FRA) has been widely recognized for transformer winding deformation detection and assessment. In this paper, frequency response functions (FRFs) are obtained by two different FRA measurement connection ways, namely, end-to-end voltage ratio (EE) and transfer voltage (TF) ratio measurements. At the same time, according to the two ways, sensitivities of the FRFs to electrical parameters of the equivalent circuit model of the transformer winding are investigated. Based on Tellegen theorem, adjoint network method is derived to calculate the values of the sensitivities of FRFs to electrical parameters. Meanwhile, the sensitivity characteristics of circuit parameters are studied. In addition, by comparing the sensitivity results of the two ways, the variation laws of the sensitivities under the two different connection approaches are determined. Besides, this paper can provide a new and objective method to interpret the FRA results and give us a better understanding how much the parameter variations can influence the FRA measurement results.

A test method of winding deformation excited by pseudorandom M-Sequences — Part I: Theory and simulation

A test method to detect winding deformation by using pseudorandom binary M-Sequence excitation signals is proposed. This broadband excitation signal and the corresponding response from the winding are combined to obtain the analytic expression of the winding's transfer function by using a Recursive Least Square method. The coefficients, poles, and zeros of the transfer function can be used to describe the winding status, and any mechanical changes in the winding over time can be therefore detected. The steps and algorithms involved in using the M-Sequence method are presented, and a comparative simulation between the M-Sequence method and Frequency Response Analysis (FRA) is carried out using an equivalent circuit for the winding. Results of the simulation confirm that the response sensitivity of the M-Sequence method is as good as FRA in a common frequency band, and is actually more sensitive for slight winding deformations of series capacitance. The correlation factor of the transfer function coefficients, used as example, can also diagnose slight deformation. Additionally, significant differences exist in the map of the poles and/or zeros before and after deformation. The study confirms the feasibility of using the M-Sequence method for detection of winding deformation in transformers. Transfer function can have a wider application than frequency response curves, then analysis and judgment based on the transfer function may offer more analysis tools. The theory and simulation study of the new method provide supports for subsequent development of its corresponding detecting system as well as experimental research.

A transformer winding deformation detection method based on the analysis of leakage inductance changes

Abstract The detection of transformer winding deformation caused by short-circuit current is of great significance to the realization of condition based maintenance. Considering the influence of environment and measurement errors, an online deformation detection method is proposed based on the analysis of leakage inductance changes. First, the operation expressions are derived on the basis of the equivalent circuit and the leakage inductance parameters are identified by the partial least squares regression algorithm. Second, the amount of the leakage inductance samples in a detection time window is determined using the Monte Carlo simulation thought, and then the samples in the confidence interval are obtained. Last, a criteria is built by the mean value changes of the leakage inductance samples and the winding deformation is detected. The online detection method considers the random fluctuation characteristics of the leakage inductance samples, adjust the threshold value automatically, and can quantify the change range to assess the severity. Based on the field data, the distribution of the leakage inductance samples is analyzed to obey the normal function approximately. Three deformation experiments are done by different sub-winding connections and the detection results verify the effectiveness of the proposed method

The On-Line Monitoring of the Winding Deformation of Transformer Based on the Improved Ultrasonic Ranging Method

The assessment of the winding deformation of transformer has a certain practical significance. In this paper, an Improved Ultrasonic Ranging (IUR) method is proposed to assess the winding deformation of transformer. Firstly, the basic principle of winding deformation detection using ultrasonic and the working principle of detection device are discussed. Secondly, the impact of the factors such as transformer oil temperature and echo signal attenuation on the test results is analyzed. Then, a new IUR method is composed, which can realize the on-line monitoring of transformer winding deformation. Finally, an assessment equipment of transformer winding deformation based on the online monitoring is developed, and a prototype is used to test the transformer mode, proving that this method is feasible.

Frequency response analysis and short-circuit impedance measurement in detection of winding deformation within power transformers

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].

Detection of power transformer winding deformation and variation of measurement connections using a hybrid winding model

This paper employs a hybrid model of a disc-type transformer winding for frequency response analysis (FRA) of winding deformation and measurement parameter influence. The model is based on multi-conductor transmission line (MTL) theories and treats every disc of a transformer winding as a transmission line. Three types of winding deformation and two types of measurement connection variation have been simulated by changing the values of the corresponding electrical parameters. Meanwhile, the frequency range of FRA is extended to 10MHz. Various scenarios have been included in the simulation studies and two statistical indicators have been adopted in result analysis. Simulation studies have shown that winding deformation and measurement connection variation can be reflected in frequency response by changing certain parameters of the hybrid model. Simulation results also suggest the frequency ranges in which the failure modes are most distinguishable and their characteristics.

On-site PD Diagnostics, FRA and Moisture Measurement for Power Transformers

The paper presents three methods for condition assessment of power transformers which can be applied on-site. A combination of UHF and acoustic partial discharge (PD) measurement methods enables to detect PD in power transformers and to improve interpretation and localisation of their sources. Frequency response measurements are a widely applied technique for power transformer winding deformation detection. Dielectric response methods deliver results about the moisture condition of a transformer.

Application of Multi-Fractal Spectrum to Analysis the Vibration Signal of Power Transformer for the Detection of Winding Deformation

The method of monitoring the tank vibration is becoming an effective method to detect the winding deformation of power transformer for the reliable and secure operation of power system. In order to further identify the relationship between the winding deformation fault of power transformer and the measured tank vibration signals, the short-circuit test is done in a 220kV transformer with the developed vibration measurement system and the vibration frequency response curves for some pre-setting winding deformation faults are obtained. Multi-fractal spectrum is applied to analyze the of the obtained vibration signals when winding conditions of power transformer are changed. It is shown that multi-fractal spectrum can effectively indicate the geometric structure features of vibration signals. The parameter variations of multi-fractal spectrum are agreed well with the preset winding faults, which provides another method for the feature extraction of vibration signal to detect the winding deformation of power transformer.