scholarly journals Adaptive Single-Pole Auto-Reclosing Scheme Based on Secondary Arc Voltage Harmonic Signatures

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1311
Author(s):  
Joon Han ◽  
Chul-Moon Lee ◽  
Chul-Hwan Kim
Keyword(s):  
Power Transmission ◽  
Harmonic Distortion ◽  
Extinction Time ◽  
Arc Voltage ◽  
Ground Fault ◽  
Fault Type ◽  
Korean Study ◽  
Harmonic Components ◽  
The Time Domain ◽  
Short Time

This paper presents an advanced adaptive single-pole auto-reclosing (ASPAR) scheme based on harmonic characteristics of the secondary arc voltage. For analysis of the harmonics, short-time Fourier transform (STFT), which is a universal signal processing tool for transforming a signal from the time domain to the frequency domain, is utilized. STFT is applied to extract the abnormal harmonic signature from the voltage waveform of a faulted phase when a transient or permanent fault occurs on a power transmission line. The proposed scheme uses the total harmonic distortion (THD) factor to determine the fault type based on the variation and distortion characteristics of the harmonics. Harmonic components in the order of odd/even are also utilized to detect the secondary arc extinction time and guide the reclosing operation. Based on these factors, two coordinated algorithms are proposed to reduce the unnecessary dead time in conventional auto-reclosing methods and enable an optimal reclosing operation in the event of a single-pole to ground fault. The proposed ASPAR scheme is implemented using the electromagnetic transient program (EMTP), and various simulations are conducted for actual 345 and 765 kV Korean study systems.

scholarly journals Investigation of Supra-Harmonics through Signal Processing Methods in Smart Grids

2017 ◽  
Vol 2 (2) ◽  
pp. 80
Author(s):  
Turgay Yalcin ◽  
Muammer Ozdemir ◽  
Pawel Kostyla ◽  
Zbigniew Leonowicz
Keyword(s):  
Electromagnetic Interference ◽  
Smart Grids ◽  
Communication Systems ◽  
Harmonic Distortion ◽  
Research Area ◽  
Ensemble Empirical Mode Decomposition ◽  
Mode Decomposition ◽  
Harmonic Components ◽  
Signal Processing Methods ◽  
Short Time

Nowadays supra-harmonic distortion studies are gaining attention day by day in power quality research area. When handling communication systems especially Power Line Carrier (PLC) systems in frequency range 2- 150 kHz, they are suitable for causing electromagnetic interference (EMI) to other systems. This study shows results of analysis employing advanced method called ensemble empirical mode decomposition (EEMD) to describe supra-harmonic distortion. Unlike the traditional method (short time fourier transform- STFT), EEMD gives extensive representation for supra-harmonic components

scholarly journals Ultrasonic Assessment of Thickness and Bonding Quality of Coating Layer Based on Short-Time Fourier Transform and Convolutional Neural Networks

Coatings ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 909
Author(s):  
Azamatjon Kakhramon ugli Malikov ◽  
Younho Cho ◽  
Young H. Kim ◽  
Jeongnam Kim ◽  
Junpil Park ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Coating Layer ◽  
Ultrasonic Pulse ◽  
Short Time Fourier Transform ◽  
Coating Materials ◽  
Time Frequency ◽  
High Attenuation ◽  
Bonding State ◽  
The Time Domain ◽  
Short Time

Ultrasonic non-destructive analysis is a promising and effective method for the inspection of protective coating materials. Offshore coating exhibits a high attenuation rate of ultrasonic energy due to the absorption and ultrasonic pulse echo testing becomes difficult due to the small amplitude of the second echo from the back wall of the coating layer. In order to address these problems, an advanced ultrasonic signal analysis has been proposed. An ultrasonic delay line was applied due to the high attenuation of the coating layer. A short-time Fourier transform (STFT) of the waveform was implemented to measure the thickness and state of bonding of coating materials. The thickness of the coating material was estimated by the projection of the STFT into the time-domain. The bonding and debonding of the coating layers were distinguished using the ratio of the STFT magnitude peaks of the two subsequent wave echoes. In addition, the advantage of the STFT-based approach is that it can accurately and quickly estimate the time of flight (TOF) of a signal even at low signal-to-noise ratios. Finally, a convolutional neural network (CNN) was applied to automatically determine the bonding state of the coatings. The time–frequency representation of the waveform was used as the input to the CNN. The experimental results demonstrated that the proposed method automatically determines the bonding state of the coatings with high accuracy. The present approach is more efficient compared to the method of estimating bonding state using attenuation.

Optimized Mooring Line Simulation Using a Hybrid Method Time Domain Scheme

2014 ◽  
Author(s):  
Niels Hørbye Christiansen ◽  
Per Erlend Torbergsen Voie ◽  
Jan Høgsberg ◽  
Nils Sødahl
Keyword(s):  
Hybrid Method ◽  
Time Domain ◽  
Computation Time ◽  
Mooring Line ◽  
Mooring Lines ◽  
Fem Model ◽  
Input Variables ◽  
The Time Domain ◽  
The Cost ◽  
Short Time

Dynamic analyses of slender marine structures are computationally expensive. Recently it has been shown how a hybrid method which combines FEM models and artificial neural networks (ANN) can be used to reduce the computation time spend on the time domain simulations associated with fatigue analysis of mooring lines by two orders of magnitude. The present study shows how an ANN trained to perform nonlinear dynamic response simulation can be optimized using a method known as optimal brain damage (OBD) and thereby be used to rank the importance of all analysis input. Both the training and the optimization of the ANN are based on one short time domain simulation sequence generated by a FEM model of the structure. This means that it is possible to evaluate the importance of input parameters based on this single simulation only. The method is tested on a numerical model of mooring lines on a floating off-shore installation. It is shown that it is possible to estimate the cost of ignoring one or more input variables in an analysis.

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.

scholarly journals Effect of the Harmonic Voltage Distortion on the Efficiency of a Compact Fluorescent Lamp

2020 ◽  
Vol 29 (54) ◽  
pp. e11604
Author(s):  
Esteban Rojas-Osorio ◽  
Andrés Julián Saavedra-Montes ◽  
Carlos Andrés Ramos-Paja
Keyword(s):  
Mathematical Model ◽  
Test Bench ◽  
Harmonic Distortion ◽  
Fluorescent Lamp ◽  
Constant Frequency ◽  
Voltage Distortion ◽  
Variable Voltage ◽  
Harmonic Voltage ◽  
Compact Fluorescent Lamp ◽  
Harmonic Components

This paper evaluates the effect of the voltage harmonic distortion over the efficiency of a compact fluorescent lamp that is fed with a constant RMS voltage and constant frequency. Several works have been published about the assessment of compact fluorescent lamps, but the effect of the voltage distortion over the efficiency is still an open topic. This work focuses on designing an experiment to estimate the efficiency of a compact fluorescent lamp while changing the voltage harmonic distortion of the power supply. First, a mathematical model that represents a bus susceptible to harmonic distortion (high impedance) that feeds the compact fluorescent lamp is analyzed. Then the mathematical model is reproduced through a test bench in a laboratory of rotating electrical machines. The test bench produces a three-phase bus with constant voltage and frequency, and variable voltage harmonic distortion. The compact fluorescent lamp is subjected to varying harmonic voltage distortion while recording its electrical variables and the produced lumens to estimate its efficiency. That is a practical approach to calculate the lamp efficiency while several works limit their scope measuring only the efficiency of the input converter. The experimental results show that a variation of the voltage harmonic distortion of 8 % on a compact fluorescent lamp reduces its efficiency. Those results put into evidence the importance of regulating harmonic distortion limits to reduce or prevent the increment of power losses caused by harmonic components.

scholarly journals Time-Domain Circuit Modelling for Hybrid Supercapacitors

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6837
Author(s):  
Fabio Corti ◽  
Michelangelo-Santo Gulino ◽  
Maurizio Laschi ◽  
Gabriele Maria Lozito ◽  
Luca Pugi ◽  
...  
Keyword(s):  
Time Domain ◽  
Black Box ◽  
Circuit Modeling ◽  
Hybrid Supercapacitor ◽  
Hybrid Supercapacitors ◽  
Linear Behavior ◽  
Modeling Techniques ◽  
The Time Domain ◽  
Short Time ◽  
Circuit Modelling

Classic circuit modeling for supercapacitors is limited in representing the strongly non-linear behavior of the hybrid supercapacitor technology. In this work, two novel modeling techniques suitable to represent the time-domain electrical behavior of a hybrid supercapacitor are presented. The first technique enhances a well-affirmed circuit model by introducing specific non-linearities. The second technique models the device through a black-box approach with a neural network. Both the modeling techniques are validated experimentally using a workbench to acquire data from a real hybrid supercapacitor. The proposed models, suitable for different supercapacitor technologies, achieve higher accuracy and generalization capabilities compared to those already presented in the literature. Both modeling techniques allow for an accurate representation of both short-time domain and steady-state simulations, providing a valuable asset in electrical designs featuring supercapacitors.

Improved Mayr Model of Electrical Arc Furnace to Analyse Harmonic

2011 ◽  
Vol 110-116 ◽  
pp. 1762-1766
Author(s):  
A.M. Zare Zadeh ◽  
R. Ghandehari
Keyword(s):  
Power Quality ◽  
Time Domain ◽  
Arc Furnace ◽  
Negative Effects ◽  
The Real ◽  
Electrical Arc ◽  
Real Behavior ◽  
Voltage Flicker ◽  
Harmonic Components ◽  
The Time Domain

Voltage flicker and harmonics are power quality problems which are imposed on power system by electrical arc furnace. To study furnaces and find a solution to remove the negative effects of them, it is needed to have an appropriate electrical arc furnace model. Several methods in time and frequency domain have been presented. One of the time domain methods is Mayr model which has two problems. Firstly, it shows the harmonic components more than the real values. Secondly, it does not involve voltage flicker phenomenon. In this article with the comparison of harmonic components of Mayr model and measured values of arc furnace, an improved Mayr model is introduced. In the presented model, the problems of Mayr model are removed and it shows the real behavior of arc furnace

scholarly journals Application of the Acoustic Emission Method for Diagnosis of On-Load Tap Changer

2017 ◽  
Vol 42 (1) ◽  
pp. 29-35 ◽  
Author(s):  
Henryk Majchrzak ◽  
Andrzej Cichoń ◽  
Sebastian Borucki
Keyword(s):  
Acoustic Emission ◽  
Frequency Domain ◽  
Time Domain ◽  
Operating Conditions ◽  
Time Frequency ◽  
Measurement Results ◽  
Tap Changer ◽  
The Time Domain ◽  
Load Tap Changer ◽  
Short Time

Abstract This paper provides an example of the application of the acoustic emission (AE) method for the diagnosis of technical conditions of a three-phase on-load tap-changer (OLTC) GIII type. The measurements were performed for an amount of 10 items of OLTCs, installed in power transformers with a capacity of 250 MVA. The study was conducted in two different OLTC operating conditions during the tapping process: under load and free running conditions. The analysis of the measurement results was made in both time domain and time-frequency domain. The description of the AE signals generated by the OLTC in the time domain was performed using the analysis of waveforms and determined characteristic times. Within the time-frequency domain the measured signals were described by short-time Fourier transform spectrograms.

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