scholarly journals Test and Research on Noise Distribution Characteristics of 220kV Oil-immersed Transformer

2021 ◽  
Vol 2087 (1) ◽  
pp. 012031
Author(s):  
Yuchao Ma ◽  
Juan Mo ◽  
Li Han ◽  
Xiang Li ◽  
Qingming Xiao
Keyword(s):  
Noise Source ◽  
Power Transformer ◽  
Great Influence ◽  
Noise Distribution ◽  
Test Results ◽  
Distribution Law ◽  
Large Power ◽  
Noise Radiation ◽  
Test Conditions ◽  
Noise Evaluation

Abstract Large power transformer is the main noise source of substation. With the increase of voltage grade and rated capacity, the noise radiation value of power equipment continues to increase, which has a great influence on the noise standard of substation boundary. In this paper, two test conditions of no-load voltage and load current are considered. The transformer noise testing datum is constructed. The distribution law of factory noise SPL of 220kV oil-immersed transformer is obtained. The test results provide accurate test data for transformer factory noise evaluation.

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.

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.

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

Answering the Questions of the Psychologist Assessing the Visually Handicapped Child

1975 ◽  
Vol 69 (8) ◽  
pp. 350-353
Author(s):  
John L. Morse
Keyword(s):  
Classroom Observation ◽  
Handicapped Child ◽  
Test Results ◽  
Visual Condition ◽  
Inappropriate Behaviors ◽  
Test Conditions ◽  
Visually Handicapped ◽  
First Time

The most common question asked by the psychologist who is faced for the first time with assessing a visually handicapped child are answered. The 15 questions include such areas as the required information concerning visual condition, background of the client, test conditions, the role of the parents, classroom observation, behaviors observed during testing, evaluation of test results, expectations of parents and teachers, and modification of a child's inappropriate behaviors.

scholarly journals Analysis of the Subdivision Errors of Photoelectric Angle Encoders and Improvement of the Tracking Precision of a Telescope Control System

Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 2998 ◽  
Author(s):  
Jiawei Yu ◽  
Qiang Wang ◽  
Guozhong Zhou ◽  
Dong He ◽  
Yunxia Xia ◽  
...  
Keyword(s):  
Error Compensation ◽  
Phase Error ◽  
Tracking Error ◽  
Great Influence ◽  
Measuring Error ◽  
Distribution Law ◽  
Lissajous Figure ◽  
Amplitude Error ◽  
Noise Error ◽  
Angle Encoder

Photoelectric angle encoders, working as position sensors, have a great influence on the accuracy and stability of telescope control systems (TCS). In order to improve the tracking precision of TCS, a method based on subdivision error compensation for photoelectric angle encoders is proposed. First, a mathematical analysis of six types of subdivision errors (DC error, phase error, amplitude error, harmonic error, noise error, and quantization error) is presented, which is different from the previously used analysis based on the Lissajous figure method. In fact, we believe that a mathematical method is more efficient than the figure method for the expression of subdivision errors. Then, the distribution law and period length of each subdivision error are analyzed. Finally, an error compensation algorithm is presented. In a real TCS, the elevation jittering phenomenon occurs, which indicates that compensating for the amplitude error is necessary. A feed-forward loop is then introduced into the TCS, which is position loop- and velocity loop-closed, leading to a decrease of the tracking error by nearly 54.6%, from 2.31” to 1.05”, with a leading speed of 0.25°/s, and by 40.5%, from 3.01” to 1.79”, with a leading speed of 1°/s. This method can realize real-time compensation and improve the ability of TCS without any change of the hardware. In addition, independently of the environment and the kind of control strategy used, this method can also improve the tracking precision presumably because it compensates the measuring error inside the photoelectric angle encoder.

scholarly journals Simulation of loop test conditions for the modified SM reactor fuel rods and test results in justification of their performance

2013 ◽  
Vol 2013 (2) ◽  
pp. 105-113
Author(s):  
Vladimir Aleksandrovich Starkov ◽  
Fedoseev V.E. Fedoseev ◽  
Shishin V.Yu. Shishin
Keyword(s):  
Reactor Fuel ◽  
Test Results ◽  
Fuel Rods ◽  
Test Conditions

scholarly journals Fatigue Life Prediction of Rolling Bearings Based on Modified SWT Mean Stress Correction

2020 ◽  
Author(s):  
Aodi Yu ◽  
Hong-Zhong Huang ◽  
Yan-Feng Li ◽  
He Li ◽  
Ying Zeng
Keyword(s):  
Fatigue Life ◽  
Life Prediction ◽  
Stress Ratio ◽  
Prediction Models ◽  
Great Influence ◽  
Sensitivity Coefficient ◽  
Model Verification ◽  
Mean Stress ◽  
Test Results ◽  
Rolling Bearings

Abstract Mean stress has a great influence on fatigue life, commonly used stress-based life prediction models can only fit the test results of fatigue life under specific stress ratio or mean stress but cannot describe the effect of stress ratio or mean stress on fatigue life. Smith, Watson and Topper (SWT) proposed a simple mean stress correction criterion. However, the SWT model regards the sensitivity coefficient of all materials to mean stress as 0.5, which will lead to inaccurate predictions for materials with a sensitivity coefficient not equal to 0.5. In this paper, considering the sensitivity of different materials to mean stresses, compensation factor is introduced to modify the SWT model, and several sets of experimental data are used for model verification. Then, the proposed model is applied to fatigue life predictions of rolling bearings, and the results of proposed method are compared with test results to verify its accuracy.

Calculation and Analysis of Reinforced Concrete Continuous Box-Girder Overpass

2011 ◽  
Vol 101-102 ◽  
pp. 463-466
Author(s):  
Dong Yu Ji
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Simulation Analysis ◽  
Great Influence ◽  
Distribution Law ◽  
Box Girder ◽  
Common Structure ◽  
Element Simulation ◽  
Stress And Deformation ◽  
Calculation Software

Reinforced concrete continuous box-girder overpass is a common structure form, Wangzhuang overpass is example, this paper adopts universal finite element calculation software to carry out finite element simulation analysis for reinforced concrete continuous box-girder overpass. Considering the influence of overpass structure weight and driveway load, the distribution law of overpass stress and displacement were researched. Analysis results show that, load’s short-term effect combination has great influence on overpass structure, driveway slanting load’s influence on overpass structure’s stress and deformation can not be ignored.

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