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Hesham B. Elrefaie

Bio: Hesham B. Elrefaie is an academic researcher from Alexandria University. The author has contributed to research in topics: Fault (power engineering) & Wavelet transform. The author has an hindex of 4, co-authored 8 publications receiving 64 citations.

Papers
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Proceedings ArticleDOI
20 Jul 2008
TL;DR: In this paper, a strategy to choose a suitable mother wavelet for power system transients is described and the simulation results show that the theoretical Daubechies wavelet is more suitable for analyzing power system fault transients than the Matlab db wavelet.
Abstract: In the literature, wavelet techniques are proposed for the analysis of power system transients. Many mother wavelets have been used for this analysis such as Haar, Daubechies (db), Symlets, and Coiflets. This paper describes a strategy to choose a suitable mother wavelet for this analysis. It also shows the deviation between Matlab and theoretical (mathematically calculated) db-wavelets when they are used for the analysis of power system transient. The simulation study is carried out using PSCAD simulation program and Matlab wavelet toolbox. The simulation results show that the theoretical db wavelet is more suitable for analyzing power system fault transients than the Matlab db wavelet.

37 citations

Proceedings ArticleDOI
25 Jul 2010
TL;DR: In this paper, a technique to eliminate the effect of decaying direct current (DC) component on DFT based phasor estimation is described. But this technique is based on estimating the phasors of a sinusoidal wave corrupted by a DC component at an instant of time.
Abstract: This paper describes a novel technique to eliminate the effect of decaying direct current (DC) component on DFT based phasor estimation. This technique is based on estimating the phasor of a sinusoidal wave corrupted by a DC component at an instant of time. Another phasor is estimated after half cycle from the instant of estimating the first one. The two phasors are added and a mathematical expression for the decaying DC component is derived. A phasor corresponding to the decaying DC component is calculated from this mathematical expression. The decaying DC component can be eliminated by subtracting this phasor from the phasor corresponding to a sinusoidal component corrupted by a DC component. The simulation results show the accuracy of the algorithm in calculating the fundamental phasor value regardless of the DC content in the input signal. This technique is compared to the most recent techniques for eliminating the effect of DC component on the DFT based phasor estimation methods.

17 citations

Proceedings ArticleDOI
22 Jul 2012
TL;DR: In this article, the authors proposed a fault detection method based on the arrival time of the reflected voltage wave from the fault point to estimate the location of the fault, which works off-line utilizing voltage samples that are recorded prior to circuit breaker tripping.
Abstract: Accurate location of faults on overhead power lines for inspection-repair purposes is of vital importance for operators and the utility staff. This paper presents a new method for accurate location of faults on two ended and three ended (teed) transmission lines. The proposed method relies on the accurate detection of the arrival time of the reflected voltage wave from the fault point to estimate the location of the fault. The method works off-line utilizing voltage samples that are recorded prior to circuit breaker tripping. Discrete wavelet transform is used to analyze the voltage samples and detail 1 is obtained. The sample number corresponding to the first peak in detail 1 represents the arrival time of the reflected wave from the fault location. A linear relationship is developed between the sample number and fault location. This relationship is used to find the fault location on two-terminal lines, series compensated lines and teed lines. The fault simulations are carried out by PSCAD and the algorithm is implemented in Matlab. Simulation results show the accuracy of the algorithm in estimating the fault location irrespective of the type of line, its voltage or length.

5 citations

Proceedings ArticleDOI
01 Dec 2017
TL;DR: In this paper, a developed arc model is introduced using MALAB and a case study for a transmission network is presented and investigated by comparing between the arc model results and field measurements of a synthetic test done for a 380 kV string insulator.
Abstract: In this paper, a developed arc model is introduced using MALAB. The developed arc model interacts with the transmission network under investigation and shows the dynamic behaviour of primary and secondary arc stages. The arc is modelled using a time-varying resistance which gets its value after solving a differential equation of arc conductance. Secondary arc extinction limits are used to determine the secondary arc duration and hence single pole autoreclsure time can be easily set. The model validation is done by comparing between the arc model results and field measurements of a synthetic test done for a 380 kV string insulator. Another case study for a transmission network is presented and investigated.

4 citations

31 Dec 2009
TL;DR: In this article, the authors developed a new basic control scheme and comprehensive analysis for a unified power flow controller (UPFC) also to develop MATLAB program which simulate the UPFC and its action on the power system.
Abstract: The main objectives of flexible AC transmission systems (FACTS) are to increase the transmission capacity of lines and to control the power flow over designated transmission system. FACTS can perform all objectives of reactive power control and voltage control within the transmission and distribution networks and at load terminals. Several schemes of flexible AC transmission systems FACTS are either in use today. One of the most important FACTS devices is the Unified Power Flow Controller (UPFC), which is used to investigate its effect on load flow and loss reduction in power system. The UPFC is a combination of a static shunt synchronous series compensator (STATCOM) and a static synchronous series compensator (SSSC), which are coupled via a common DC link. The UPFC is a device, which can control simultaneously all the three parameters of line power flow which are line impedance, voltage and phase angle. The UPFC improves terminal voltage regulation, series capacitor compensation and transmission angle regulation. The main objectives of this work are to develop a new basic control scheme and comprehensive analysis for a unified power flow controller (UPFC) also to develop MATLAB program which simulate the UPFC and its action on the power system. This developed technique showed to be very effective and it will enable engineers to study and investigate how the UPFC can affect the transmission system using the series voltage and shunt current injection. It was possible to demonstrate that the UPFC can improve the system characteristics and gives the best transient and dynamic stability. It can highly improves the power factor. Many cases are investigated and studied such as application of the UPFC to control voltage and power flow. The cases are tested for the same simulated power system but with different load types and different system voltages. In all cases, the performance of the system was analyzed, tested and studied to indicate voltages, currents and power performance and showed to be satisfactory.

4 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, a new approach in the passive islanding detection method has been studied for the grid-connected photovoltaic (PV) inverter system using the wavelet packet transform (WPT) and back propagation neural network (BPNN).
Abstract: In this paper, a new approach in the passive-islanding detection method has been studied for the grid-connected photovoltaic (PV) inverter system using the wavelet packet transform (WPT) and back propagation neural network (BPNN). This proposed method is based on the point of common coupling voltage measurement and processing of this signal with a WPT to find the normalized logarithmic energy entropy. The BPNN is used for decision-making mechanism to avoid threshold. With this technique, the islanding operation is able to detect within 40 ms. In addition, it is effective even when the power supplied by distributed generation and the power consumed by the load is matched. In order to verify the capability of the proposed method, the simulation and experimental results of a 1.2-kW PV inverter by IEC Std. 62116 are provided. The proposed technique can be applied to both single- and multi-PV systems.

63 citations

Journal ArticleDOI
TL;DR: In this study, IQR was used to determine the best-suited mother wavelet for electronic nose signals in beef quality classification and the experimental results show that IQR based mother wavelets have better capability to keep essential information from original signals than SNR, MSE, and correlation coefficient basedmother wavelets.

55 citations

Journal ArticleDOI
TL;DR: A novel traveling-wave-based fault-location algorithm for multiterminal transmission lines that based on the data measured at line terminals lack reliability and accuracy and time synchronization error is eliminated.
Abstract: A novel traveling-wave-based fault-location algorithm for multiterminal transmission lines is introduced in this paper Existing traveling-wave fault-location methods that based on the data measured at line terminals lack reliability and accuracy because time synchronization is needed, which brings error To solve this problem, the complex structure of multiterminal power system is divided into several fault identification branches, current at the midpoint of each branched is measured, a novel fault-location algorithm is proposed, and the time synchronization error is eliminated A line-based device is designed to measure the current at the midpoint of each branch An accurate value of the traveling wave speed can be obtained by merely applying the data record in one measuring device Thus, the fault-location accuracy is improved The system model applied in this paper comprises one transmission line and two tapped lines, and the proposed method applies to networks with more terminals Performance of this method is tested by different cases by PSCAD The hardware platform has been tested in Sichuan Province, China

52 citations

Journal ArticleDOI
TL;DR: In this article, a new auxiliary signal is introduced based on a simple high-frequency modulation of the fault current, and sample-summation of both fault current and auxiliary signal are calculated, for each one-cycle-length data stream.
Abstract: This paper proposes a new fast algorithm to estimate the fundamental phasor of fault current signals, based on discrete Fourier transform (DFT). Since fault currents include decaying dc component (ddc), DFT-based algorithms have inaccuracy in phasor estimation. The proposed algorithm consists of four steps. First, a new auxiliary signal is introduced based on a simple high-frequency modulation of the fault current. Then, DFT of the fault current and sample-summation of both fault current and auxiliary signal are calculated, for each one-cycle-length data stream. Next, DFT estimation error due to the ddc is calculated. Finally, by removing this error, accurate fundamental phasor is obtained. This paper uses an innovative and accurate formulation based on notations of signal processing literature. To validate the proposed algorithm, several computer-simulated signals and an electromagnetic transient program-generated signal are employed. The proposed algorithm is compared with recent phasor estimation methods, using wide variety of test signals. Standard indices of rise time, settling time, and percentage overshoot are used for comparison. These comparisons show that the proposed algorithm has robust performance in off-nominal frequency condition, and presence of harmonics, noise and multiple ddc components. Moreover, it provides faster convergence speed and lower computation burden.

37 citations

Journal ArticleDOI
TL;DR: To conclude, choosing the suitable wavelet family is more important than relying on the MSE value alone to successfully perform a wavelet transformation.

34 citations