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.

Axial Nonlinear Mechanical Vibrations of Large Power Transformer Windings During Short Circuit

2001 ◽  
Author(s):  
Jian-Xue Xu ◽  
Zhen-Mao Chen
Keyword(s):  
Steady State ◽  
Shooting Method ◽  
Single Phase ◽  
Power Transformer ◽  
Short Circuit ◽  
Mathieu Equation ◽  
Response Force ◽  
Dynamical Response ◽  
Large Power ◽  
The Time Domain

Abstract In this paper, the axial nonlinear vibrations of the transformer winding under steady state operation case and short circuit case are studied in single degree and multi-degree models. In the case of having ampere-turn balance, the steady state response of the former model is obtained by using multi-scale method and periodic shooting method, analytically and numerically. At the same time, the computing method of Jacobi matrix in the periodic shooting method has been modified, so that the computing CPU time is saved. For multi-degree mechanical model of a single phase transformer windings, the time domain response and relation between the response and various parameters are obtained by Runge-Kutta method. For ampere-turn unbalance case, an electric-mechanical coupled problem, that the electric force depends the displacement of the winding are foomed, and the nonlinear forced Mathieu equation is established for this problem; and then the nonlinear dynamical response and global dynamical behaviors are analyzed. Finally, for a 20 MVA single phase three windings transformer, a series of short circuit experiments have been performed and the axial dynamical response force, magnetic field, strain etc. have been measured. The theoretical results well agree with the experimental results.

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 A Numerical Study on the Combustion Process and Emission Characteristics of a Natural Gas-Diesel Dual-Fuel Marine Engine at Full Load

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1342
Author(s):  
Van Chien Pham ◽  
Jae-Hyuk Choi ◽  
Beom-Seok Rho ◽  
Jun-Soo Kim ◽  
Kyunam Park ◽  
...  
Keyword(s):  
Natural Gas ◽  
Combustion Process ◽  
Simulation Software ◽  
Dual Fuel ◽  
Injection Timing ◽  
Emission Characteristics ◽  
Cylinder Pressure ◽  
Marine Engine ◽  
Full Load ◽  
Simulation Results

This paper presents research on the combustion and emission characteristics of a four-stroke Natural gas–Diesel dual-fuel marine engine at full load. The AVL FIRE R2018a (AVL List GmbH, Graz, Austria) simulation software was used to conduct three-dimensional simulations of the combustion process and emission formations inside the engine cylinder in both diesel and dual-fuel mode to analyze the in-cylinder pressure, temperature, and emission characteristics. The simulation results were then compared and showed a good agreement with the measured values reported in the engine’s shop test technical data. The simulation results showed reductions in the in-cylinder pressure and temperature peaks by 1.7% and 6.75%, while NO, soot, CO, and CO2 emissions were reduced up to 96%, 96%, 86%, and 15.9%, respectively, in the dual-fuel mode in comparison with the diesel mode. The results also show better and more uniform combustion at the late stage of the combustions inside the cylinder when operating the engine in the dual-fuel mode. Analyzing the emission characteristics and the engine performance when the injection timing varies shows that, operating the engine in the dual-fuel mode with an injection timing of 12 crank angle degrees before the top dead center is the best solution to reduce emissions while keeping the optimal engine power.

Large power transformer reliability modeling

2014 ◽  
Vol 7 (S1) ◽  
pp. 9-17 ◽  
Author(s):  
Mahfoud Chafai ◽  
Larbi Refoufi ◽  
Hamid Bentarzi
Keyword(s):  
Power Transformer ◽  
Reliability Modeling ◽  
Large Power

Analysis of HPDC Process with Automobile Part (Oil Pan) by CAE Simulation

2013 ◽  
Vol 753-755 ◽  
pp. 1318-1323 ◽  
Author(s):  
Kwang Kyu Seo ◽  
Hong Kyu Kwon
Keyword(s):  
Die Casting ◽  
Simulation Software ◽  
Filling Process ◽  
Solidification Shrinkage ◽  
Automobile Part ◽  
Computer Aided ◽  
Gate System ◽  
Simulation Results ◽  
Casting Design ◽  
Cae Simulation

In this research, Computer Aided Engineering (CAE) simulation was performed by using the simulation software (AnyCasting) in order to optimize casting design of an automobile part (Oil Pan_7G9E) which is well known and complicated to achieve a good casting layout. The simulation results were analyzed and compared carefully in order to apply them into the production die-casting mold. During the filling process, internal porosities caused by air entrap were predicted and reduced remarkably by the modification of the gate system and the configuration of overflow. With the solidification analysis, internal porosities caused by the solidification shrinkage were predicted and reduced by the modification of the gate system.

scholarly journals Barycenter Theorem in Phase Characteristics of Symmetric and Asymmetric Windows

Symmetry ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 329
Author(s):  
Jiufei Luo ◽  
Haitao Xu ◽  
Kai Zheng ◽  
Xinyi Li ◽  
Song Feng
Keyword(s):  
Frequency Estimation ◽  
Random Noise ◽  
Estimation Algorithm ◽  
Frequency Component ◽  
Phase Response ◽  
Numeric Simulation ◽  
Simulation Results ◽  
The Time Domain ◽  
Short Time ◽  
The Relationship

Asymmetric windows are of increasing interest to researchers because of the nonlinear and adjustable phase response, as well as alterable time delay. Short-time phase distortion can provide an essential improvement in speech coding, and also has better performance in speech recognition. The merits of asymmetric windows in the aspect of spectral behaviors have an important function in frequency component detection and parameter estimation. In this paper, the phase response of windows were further studied, and the phase characteristics of symmetric and asymmetric windows are described. The relationship between the barycenter of windows in the time domain, and the phase characteristic at the center of the main lobe in the frequency domain, was established. In light of the relationship, an improved version of the asymmetric window- based frequency estimation algorithm was proposed. The improved algorithm has advantages of straightforward implementation and computational efficiency. The numeric simulation results also indicate that the improved approach is more robust than the traditional method against additive random noise.

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