Lociranje parcijalnih pražnjenja u energetskom transformatoru primenom UHF tehnike

2021 ◽  
Vol 23 (2) ◽  
pp. 73-78
Author(s):  
Đorđe Dukanac
Keyword(s):  
Power Transformer ◽  
Maximum Amplitude ◽  
Threshold Value ◽  
Partial Discharges ◽  
Tank Model ◽  
Large Power ◽  
Arrival Times ◽  
Actual Signal ◽  
Different Shapes ◽  
Actual Shape

A specially developed algorithm used in the program in MATLAB in a simplified model of a large power transformer will determine the locations of partial discharges using four UHF sensors by simulating ten real waveforms from a source of partial discharges. Subsequent interpolation of the recorded signals will be performed, in order to obtain the closest possible shapes to the actual waveforms. Actual waveforms were obtained by experimenting with a single UHF sensor in a real large power transformer. The ten signals of the actual shape are mutually different heights of the initial several peaks and different shapes, but still have similar maximum amplitude, frequency spectrum and the prevailing frequency of the most prominent partial discharges. It was important to determine where the actual signal begins, for which a unique calculation procedure was made, and later to accurately determine the differences between the occurrences of the first (reference) peaks of the actual signals at individual sensors. The most favourable threshold value was taken into account when determining the differences in signal arrival times by the method of the first acceptable peak. The deviations in the calculated positions of the sources of partial discharges obtained for 120 randomly selected points in the volume of the transformer tank model will be analysed.

The influence of ultrasound signal parameters on sonoluminescence light intensity

2013 ◽  
Vol 62 (4) ◽  
pp. 605-612
Author(s):  
Marek Szmechta ◽  
Tomasz Boczar ◽  
Dariusz Zmarzły
Keyword(s):  
Acoustic Emission ◽  
Acoustic Waves ◽  
Power Transformer ◽  
Electrical Power ◽  
Partial Discharges ◽  
Research Project ◽  
Insulation Systems ◽  
Secondary Phenomenon ◽  
New Research ◽  
The Relationship

Abstract Topics of this article concern the study of the fundamental nature of the sonoluminescence phenomenon occurring in liquids. At the Institute of Electrical Power Engineering at Opole University of Technology the interest in that phenomenon known as secondary phenomenon of cavitation caused by ultrasound became the genesis of a research project concerning acoustic cavitation in mineral insulation oils in which a number of additional experiments performed in the laboratory aimed to determine the influence of a number of acoustic parameters on the process of the studied phenomenona. The main purpose of scientific research subject undertaken was to determine the relationship between the generation of partial discharges in high-voltage power transformer insulation systems, the issue of gas bubbles in transformer oils and the generated acoustic emission signals. It should be noted that currently in the standard approach, the phenomenon of generation of acoustic waves accompanying the occurrence of partial discharges is generally treated as a secondary phenomenon, but it can also be a source of many other related phenomena. Based on our review of the literature data on those referred subjects taken, it must be noted, that this problem has not been clearly resolved, and the description of the relationship between these phenomena is still an open question. This study doesn’t prove all in line with the objective of the study, but can be an inspiration for new research project in the future in this topic. Solution of this problem could be a step forward in the diagnostics of insulation systems for electrical power devices based on non-invasive acoustic emission method.

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

scholarly journals Forecast model for estimating the service life of a diagnosed object based on the Neyman–Pearson method

2018 ◽  
Vol 216 ◽  
pp. 03011
Author(s):  
Sergey Barsukov ◽  
Sergey Pakhomov
Keyword(s):  
Service Life ◽  
Power Transformer ◽  
Impurity Content ◽  
Forecast Model ◽  
Threshold Value ◽  
Technical Condition ◽  
Transformer Oil ◽  
Average Risk ◽  
Iron Impurity ◽  
Object Based

The paper is aimed at developing a forecast model for estimating the service life of a diagnosed object based on the Neyman–Pearson method. It presents a procedure for selecting necessary and sufficient number of diagnostic indicators using the forecast model. The technique has been tested on the basis of a power transformer with a liquid dielectric. A condition-based operation strategy has been proposed for the transformer. According to this strategy, the iron impurity content in the dielectric liquid (oil) of the transformer should be measured every year of operation. Based on the forecast model, it is possible to calculate the variation of average risk (R) and a threshold value of iron impurity content in the transformer oil (k0) for each year of operation. Using these parameters, a reliable forecast model can be constructed to estimate the remaining service life of the transformer. The obtained relationships make it possible to identify a scientifically grounded stage in the service life of a diagnosed object, at which the number of measurable diagnostic indicators (indicators that are necessary for assessing the real technical condition of equipment) can be minimized.

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.

scholarly journals Covert Timing Channel Analysis Either as Cyber Attacks or Confidential Applications

Sensors ◽  
2020 ◽  
Vol 20 (8) ◽  
pp. 2417 ◽  
Author(s):  
Shorouq Al-Eidi ◽  
Omar Darwish ◽  
Yuanzhu Chen
Keyword(s):  
Packet Delay ◽  
Threshold Value ◽  
Cyber Attacks ◽  
Sensitive Information ◽  
Time Behavior ◽  
Timing Channels ◽  
Arrival Times ◽  
Covert Timing Channels ◽  
Timing Channel ◽  
Channel Analysis

Covert timing channels are an important alternative for transmitting information in the world of the Internet of Things (IoT). In covert timing channels data are encoded in inter-arrival times between consecutive packets based on modifying the transmission time of legitimate traffic. Typically, the modification of time takes place by delaying the transmitted packets on the sender side. A key aspect in covert timing channels is to find the threshold of packet delay that can accurately distinguish covert traffic from legitimate traffic. Based on that we can assess the level of dangerous of security threats or the quality of transferred sensitive information secretly. In this paper, we study the inter-arrival time behavior of covert timing channels in two different network configurations based on statistical metrics, in addition we investigate the packet delaying threshold value. Our experiments show that the threshold is approximately equal to or greater than double the mean of legitimate inter-arrival times. In this case covert timing channels become detectable as strong anomalies.

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