scholarly journals A Poisson-Fault Model for Testing Power Transformers in Service

2014 ◽  
Vol 2014 ◽  
pp. 1-9
Author(s):  
Dengfu Zhao ◽  
Zheng Zhao ◽  
Qihong Duan ◽  
Gongnan Xie
Keyword(s):  
Failure Rate ◽  
Working Conditions ◽  
Classical Method ◽  
Power Transformer ◽  
Fault Model ◽  
Power Transformers ◽  
Bayes Estimate ◽  
Testing Power ◽  
Simulation Results ◽  
Periodic Inspections

This paper presents a method for assessing the instant failure rate of a power transformer under different working conditions. The method can be applied to a dataset of a power transformer under periodic inspections and maintenance. We use a Poisson-fault model to describe failures of a power transformer. When investigating a Bayes estimate of the instant failure rate under the model, we find that complexities of a classical method and a Monte Carlo simulation are unacceptable. Through establishing a new filtered estimate of Poisson process observations, we propose a quick algorithm of the Bayes estimate of the instant failure rate. The proposed algorithm is tested by simulation datasets of a power transformer. For these datasets, the proposed estimators of parameters of the model have better performance than other estimators. The simulation results reveal the suggested algorithms are quickest among three candidates.

scholarly journals Novel Remanence Determination for Power Transformers Based on Magnetizing Inductance Measurements

Energies ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4616
Author(s):  
Chen Wei ◽  
Xianqiang Li ◽  
Ming Yang ◽  
Zhiyuan Ma ◽  
Hui Hou
Keyword(s):  
Numerical Simulations ◽  
Laboratory Experiments ◽  
Power Transformer ◽  
Power Transformers ◽  
Inrush Current ◽  
The Core ◽  
Novel Method ◽  
Simulation Results ◽  
Electro Magnetic ◽  
The Relationship

The remanence (residual flux) in the core of power transformers needs to be determined in advance to eliminate the inrush current during the process of re-energization. In this paper, a novel method is proposed to determine the residual flux based on the relationship between residual flux and the measured magnetizing inductance. The paper shows physical, numerical, and analytical explanations on the phenomenon that the magnetizing inductance decreases with the increase of residual flux under low excitation. Numerical simulations are performed by EMTP (Electro-Magnetic Transient Program) on a 1 kVA power transformer under different amounts of residual flux. The inductance–remanence curves are nearly the same when testing current changes. Laboratory experiments conducted on the same transformer are in line with the numerical simulations. Furthermore, numerical simulation results on a 240 MVA are reported to demonstrate the effectiveness of the proposed method.

scholarly journals Analyzing Ferroresonance Phenomena in Power Transformers Including Zinc Oxide Arrester and Neutral Resistance Effect

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Hamid Radmanesh ◽  
Fathi Seyed Hamid
Keyword(s):  
Zinc Oxide ◽  
Power System ◽  
Power Transformer ◽  
Periodic Oscillation ◽  
Power Transformers ◽  
System Configuration ◽  
Fundamental Resonance ◽  
Short Period ◽  
Simulation Results ◽  
Nonlinear Resistance

This paper studies the effect of zinc oxide arrester (ZnO) and neutral earth resistance on controlling nonconventional oscillations of the unloaded power transformer. At first, ferroresonance overvoltage in the power system including ZnO is investigated. It is shown this nonlinear resistance can limit the ferroresonance oscillations but it cannot successfully control these phenomena. Because of the temperature dissipation of ZnO, it can withstand against overvoltage in a short period and after that ferroresonance causes ZnO failure. By applying neutral earth resistance to the system configuration, mitigating ferroresonance has been increased and chaotic overvoltage has been changed to the smoother behavior such as fundamental resonance and periodic oscillation. The simulation results show that connecting the neutral resistance exhibits a great mitigating effect on nonlinear overvoltage.

scholarly journals Influence of the load of the power transformer on the magnetizing current

2021 ◽  
Vol 2131 (4) ◽  
pp. 042097
Author(s):  
S Ivankov ◽  
S Zagulyaev ◽  
D Gukov
Keyword(s):  
Cross Section ◽  
Magnetic Circuit ◽  
Power Transformer ◽  
Magnetic Core ◽  
Significant Error ◽  
Continuous Operation ◽  
Power Transformers ◽  
Magnetic Scattering ◽  
Testing Power ◽  
Magnetizing Current

Abstract Data on the magnetizing current of power transformers are taken from the experience of idling. It is considered that it does not change under load. The experience of idling does not take into account the uneven saturation of the magnetic core when working under load. The hypothesis of a significant error caused by this assumption is put forward. The experiments carried out confirmed the hypothesis. The differences in the measurement of the magnetizing current at idle and under load in the experiments reached 28-32%. This determines the inaccuracy in the calculations of currents and losses in power transformers, which, taking into account the continuous operation of transformers and their large number, can be significant. It is proposed to add the experience of working at rated load when testing power transformers. This experience will not only allow us to clarify the val-ue of the magnetizing current under load and magnetic losses, but also to re-fine the design of the transformer in the direction of reducing the magnetizing current by eliminating uneven saturation of the magnetic circuit when working under load, due to the influence of magnetic scattering fields. This is possible by locally increasing the cross-section of the magnetic circuit in the busiest places of the magnetic circuit.

Power Transformers Fault Diagnosis Based on DRNN

2014 ◽  
Vol 960-961 ◽  
pp. 700-703
Author(s):  
Hui Da Duan ◽  
Qiao Song Li
Keyword(s):  
Fault Diagnosis ◽  
Prediction Error ◽  
Power Transformer ◽  
Gas Analysis ◽  
Bp Algorithm ◽  
Power Transformers ◽  
Dissolved Gas ◽  
Simulation Results ◽  
Recursive Prediction ◽  
Transformer Fault

In recent years, improved three-ratio is an effective method for transformer fault diagnosis based on Dissolved Gas Analysis (DGA). In this paper, diagonal recurrent neural network (DRNN) is used to resolve the online fault diagnosis problems for oil-filled power transformer based on DGA. To overcome disadvantages of BP algorithm, a new recursive prediction error algorithm (RPE) is used in this paper.In addition, to demonstrate the effectiveness and veracity of the proposed method, some cases are used in the simulation. The simulation results are satisfactory.

A Solid-State On-Load Tap Changer for the Power Transformers of 10—0.4 kV Distribution Networks

Vestnik MEI ◽  
2020 ◽  
Vol 6 (6) ◽  
pp. 82-90
Author(s):  
Dmitriy I. Panfilov ◽  
◽  
Mikhail G. Astashev ◽  
Aleksandr V. Gorchakov ◽  
◽  
...  
Keyword(s):  
Solid State ◽  
Physical Model ◽  
High Speed ◽  
Power Transformer ◽  
Voltage Control ◽  
Power Transformers ◽  
Control Algorithms ◽  
Load Voltage ◽  
Tap Changer ◽  
Load Tap Changer

The specific features relating to voltage control of power transformers at distribution network transformer substations are considered. An approach to implementing high-speed on-load voltage control of serially produced 10/0.4 kV power transformers by using a solid-state on-load tap changer (SOLTC) is presented. An example of the SOLTC circuit solution on the basis of thyristor switches is given. On-load voltage control algorithms for power transformers equipped with SOLTC that ensure high reliability and high-speed operation are proposed. The SOLTC performance and the operability of the suggested voltage control algorithms were studied by simulation in the Matlab/Simulink environment and by experiments on the SOLTC physical model. The structure and peculiarities of the used simulation Matlab model are described. The SOLTC physical model design and its parameters are presented. The results obtained from the simulating the SOLTC operation on the Matlab model and from the experiments on the SOLTS physical model jointly with a power transformer under different loads and with using different control algorithms are given. An analysis of the experimental study results has shown the soundness of the adopted technical solutions. It has been demonstrated that the use of an SOLTC ensures high-speed voltage control, high efficiency and reliability of its operation, and arcless switching of the power transformer regulating taps without load voltage and current interruption. By using the SOLTC operation algorithms it is possible to perform individual phase voltage regulation in a three-phase 0.4 kV distribution network. The possibility of integrating SOLTC control and diagnostic facilities into the structure of modern digital substations based on the digital interface according to the IEC 61850 standard is noted.

The Heating System of Agricultural Facilities Using Excess Heat Power Transformers

2020 ◽  
Vol 67 (1) ◽  
pp. 42-47
Author(s):  
Anatoliy I. Sopov ◽  
Aleksandr V. Vinogradov
Keyword(s):  
System Design ◽  
Heat Supply ◽  
Cooling System ◽  
Power Transformer ◽  
Electric Heating ◽  
Heating System ◽  
Power Transformers ◽  
Large Power ◽  
Excess Heat ◽  
Power Centers

In power transformers, energy losses in the form of heat are about 2 percent of their rated power, and in transformers of large power centers reach hundreds of kilowatts. Heat is dissipated into the environment and heats the street air. Therefore, there is a need to consume this thermal energy as a source of heat supply to nearby facilities. (Research purpose) To develop methods and means of using excess heat of power transformers with improvement of their cooling system design. (Materials and methods) The authors applied following methods: analysis, synthesis, comparison, monographic, mathematical and others. They analyzed various methods for consuming excess heat from power transformers. They identified suitable heat supply sources among power transformers and potential heat consumers. The authors studied the reasons for the formation of excess heat in power transformers and found ways to conserve this heat to increase the efficiency of its selection. (Results and discussion) The authors developed an improved power transformer cooling system design to combine the functions of voltage transformation and electric heating. They conducted experiments to verify the effectiveness of decisions made. A feasibility study was carried out on the implementation of the developed system using the example of the TMG-1000/10/0.4 power transformer. (Conclusions) The authors got a new way to use the excess heat of power transformers to heat the AIC facilities. It was determined that the improved design of the power transformer and its cooling system using the developed solutions made it possible to maximize the amount of heat taken off without quality loss of voltage transformation.

scholarly journals Temperature Distribution in the Insulation System of Condenser-Type HV Bushing—Its Effect on Dielectric Response in the Frequency Domain

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 4016
Author(s):  
Krzysztof Walczak ◽  
Jaroslaw Gielniak
Keyword(s):  
Temperature Distribution ◽  
Working Conditions ◽  
Dielectric Response ◽  
Power Transformers ◽  
Response Analysis ◽  
Insulation System ◽  
Large Power ◽  
Catastrophic Failures ◽  
Significant Temperature ◽  
Specific Construction

HV bushings are an important part of the equipment of large power transformers, responsible for their many serious (including catastrophic) failures. Their proper exploitation needs to apply correct and reliable diagnostics, e.g., the use of dielectric response methods, that take into account their specific construction and working conditions. In this article, based on laboratory tests carried out on a real bushing, it has been shown that the significant temperature distribution within its core significantly affects the shape of the dielectric response of its insulation; therefore, the approach to its modeling should be changed. Hence, a new method for interpreting the results, using the so-called the 2XY model, is proposed. Subsequently, based on the measurements made on the insulators in operation, a new modeling method was verified. In conclusion, it can be stated that the 2XY model significantly improves the reliability of the dielectric response analysis, which should be confirmed in the future by tests on withdrawn and revised insulators.

Research on Very Fast Transient over-Voltages Distribution in Large Power Transformer Windings

2012 ◽  
Vol 433-440 ◽  
pp. 7287-7292
Author(s):  
You Hua Gao ◽  
Zeng Feng Lai ◽  
Xiao Ming Liu ◽  
Guo Wei Liu ◽  
Ye Wang
Keyword(s):  
Power Transformer ◽  
Simulation Software ◽  
Large Power ◽  
Telegraph Equations ◽  
Backward Differentiation Formulas ◽  
Space Discretization ◽  
Simulation Results ◽  
Fast Transient ◽  
The Time Domain ◽  
Differentiation Formulas

To analyze the transient response of transformer windings under very fast transient over-voltage (VFTO), multi-conductor transmission line (MTL) model based on the representation of transformer windings by its individual turns are established. Space discretization is needed for solving the time-domain telegraph equations of MTL. To calculate the voltage distributions along transformer windings, through combining the compact finite difference (CFD) theory and the backward differentiation formulas (BDF). Simulation software ATP is introduced, and the simulation results demonstrate that the proposed approach is feasible.

Study of power transformer loading in rural power supply systems

2021 ◽  
Vol 13 (4) ◽  
pp. 282-289
Author(s):  
I. V. Naumov ◽  
D. N. Karamov ◽  
A. N. Tretyakov ◽  
M. A. Yakupova ◽  
E. S. Fedorinovа
Keyword(s):  
Energy Efficiency ◽  
Power Supply ◽  
Rural Areas ◽  
Power Transformer ◽  
Electric Energy ◽  
Power Transformers ◽  
Electric Networks ◽  
Load Factors ◽  
Optimal Load ◽  
Supply Systems

The purpose of this study is to study the effect of loading power transformers (PT) in their continuous use on their energy efficiency on a real-life example of existing rural electric networks. It is noted that the vast majority of PT in rural areas have a very low load factor, which leads to an increase in specific losses of electric energy when this is transmitted to various consumers. It is planned to optimize the existing synchronized power supply systems in rural areas by creating new power supply projects in such a way as to integrate existing power sources and ensure the most efficient loading of power transformers for the subsequent transfer of these systems to isolated ones that receive power from distributed generation facilities. As an example, we use data from an electric grid company on loading power transformers in one of the districts of the Irkutsk region. Issues related to the determination of electric energy losses in rural PT at different numerical values of their load factors are considered. A computing device was developed using modern programming tools in the MATLAB system, which has been used to calculate and plot the dependence of power losses in transformers of various capacities on the actual and recommended load factors, as well as the dependence of specific losses during the transit of 1 kVA of power through a power transformer at the actual, recommended and optimal load factors. The analysis of specific losses of electric energy at the actual, recommended and optimal load factors of PT is made. Based on the analysis, the intervals of optimal load factors for different rated power of PT of rural distribution electric networks are proposed. It is noted that to increase the energy efficiency of PT, it is necessary to reduce idling losses by increasing the load of these transformers, which can be achieved by reducing the number of transformers while changing the configuration of 0.38 kV distribution networks.

Compressive Strength Analysis of MWD Microchip Tracer

2014 ◽  
Vol 511-512 ◽  
pp. 561-564
Author(s):  
Ji Bo Li ◽  
Wei Ning Ni ◽  
San Guo Li ◽  
Zu Yang Zhu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Compressive Strength ◽  
Working Conditions ◽  
Failure Criterion ◽  
Strength Analysis ◽  
Design Phase ◽  
Key Issues ◽  
Simulation Results ◽  
Better Than

Pressure resistant performance of Measure While Drilling (MWD) microchip tracer to withstand the harsh downhole environment is one of the key issues of normal working. Therefore, it is an effective way to analyze pressure resistant performance of the tracer in the design phase. Compressive strength of the tracer was studied based on finite element method. Considering downhole complexity and working conditions during the processing of tracer roundness, material non-uniformity and other factors. In this study, researchers took sub-proportion failure criterion to determine the failure of tracer. Simulation results of two structures, with pin and without pin, show that both structures met the requirement of downhole compressive strength, and the structure with pin was better than the structure without pin. This study provides basis for downhole application of microchip tracers.

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