Showing papers by "Madjid Teguar published in 2017"

Application of SVM and KNN to Duval Pentagon 1 for transformer oil diagnosis

Abstract: The carried out investigations deal with the application of machine learning algorithms to Duval Pentagon 1 graphical method for the diagnosis of transformer oil. In fact, combined to graphical methods, pattern recognition aims to may complement. For this purpose, we have used the Support Vector Machine (SVM) and the K-Nearest Neighbor (KNN) algorithms combined to the Duval method. The SVM parameters have been optimized with the Particle Swarm Optimization (PSO). Inspired from IEC and IEEE, five classes namely PD, D1, D2, T1&T2, and T3 have been adopted. The combined algorithms were verified using 155 samples from IEC TC 10 and related databases. We found that KNN, SVM may complement the Duval Pentagon 1 diagnosis method.

Improvement of electric field distribution by integrating composite insulators in a 400 kV AC double circuit line in Algeria

Abstract: Because of their advantages over glass and porcelain insulators, composite insulators are being used now in power transmission lines for different voltage rating levels. Recently, the 400 kV level is introduced by Societe Nationale de l'Electricite et du Gaz, SONELGAZ (Algerian Company of Electric Power and Gas) where glass insulators are installed. For better electrical performances, we propose in this paper to integrate composite insulators in a three phase 400 kV AC double circuit line situated in the northwest of Algeria. A comparison is done between the already existing glass insulators and the proposed composite insulator in terms of electric field distribution. The electric field is studied along the leakage paths of the insulators under different surface conditions (dry and clean, uniformly and non uniformly polluted, and in presence of water droplets). Three composite insulators with different shed configurations are proposed. From these three configurations, we selected the insulator presenting lower electric field magnitude in critical areas mainly on the triple point junction (air — HV end — housing material interface). On the double circuit line, we focused our study on the phase insulator that presents the highest electrical stress. Impact of hardware fittings, tower, phases and conductors on the electric field distribution has been analyzed. Effects of bundled conductors have been also studied. Simulations were carried out by employing 2D Finite Element Method (FEM) using COMSOL Multiphysics® 4.3 software. Results show that electric field is lower in the case of composite insulators. Furthermore, we found that the calculation model can be simplified by not considering all circuit phases. Note that appropriate corona rings are considered on both HV and ground ends for glass and composite insulators and their geometrical parameters (corona ring diameter, corona ring tube diameter and corona ring height) are kept constant throughout the whole study.

Experimental investigation and signal processing techniques for degradation assessment of XLPE and PVC/B materials under thermal aging

Abstract: Operating conditions subject power cables insulation to a variety of stresses. Among them, the thermal constraint is considered as one of the most severe factors causing irreversible damage to the electrical insulation. In light of this, accelerated thermal aging experiment was performed on cross-linked polyethylene (XLPE) and Polyvinyl chloride class B (PVC/B) samples. This paper deals with an experimental study based on the measurement of the AC current through the insulation bulk. First, the waveform in addition to the RMS value of the current were analyzed at different aging stages and for five AC applied voltages ranging from 3 to 12 kV. Fast Fourier Transform (FFT) spectral analysis is employed to assess harmonic contents of the current signal and evaluate its total harmonic distortion (THD). Further in-depth analysis was proposed by decomposing the current into several time-frequency bands using the Discrete Wavelet Transform (DWT) method, then Standard deviation-Multi Resolution Analysis (STD-MRA) representation is adopted for the sake of determining the details that correlate with the degradation level of the both studied materials. The obtained results show that our experimental-signal processing techniques methodology could be an efficient diagnostic tool for monitoring the degradation process of insulation materials used in extruded power cables.

On the analysis of lightning response of interconnected wind turbine grounding systems

Abstract: This paper deals with the use of the transmission line approach to analyse the transient behaviour of isolated and interconnected grounding systems of wind turbines under lightning discharge. The effects of the soil resistivity as well as the grounding systems interconnection type (cascade and closed) have been studied. As main results, the interconnection leads to a decrease of the impedance and consequently on the transient potential of the grounding systems. This decline is accentuated for high soil resistivities where the discharge current requires a larger system to fast dissipate current into the ground. Also, it is shown that the closed grounding systems are more suitable than the cascade ones.

Transient behavior of vertical grounding electrode under impulse current

Abstract: This paper aims to study the transient behavior of vertical grounding electrode under impulse current and buried in homogeneous soil. We have interested to the variation of the grounding impedance as function of frequency as well as the evolution of the transient potential using Transmission Line Method (TLM) in domain time. Several current magnitudes and soil resistivities and permittivities have been considered. This study has been carried out incorporating or not the soil ionization phenomenon. The obtained results have been confronted to those found by other researcher using Hybrid Electromagnetic Method (HEM). A good accordance has been obtained. As main results, soil ionization generates a decrease of the transient potential. Such decease is accentuated for high current magnitudes and high soil resistivities.

Incorporation of soil ionization and mutual coupling in transient study of horizontal grounding electrode using TLM

Abstract: This investigation is devoted to study the transient behavior of long horizontal grounding conductor submitted to high impulse current using Transmission Line Method (TLM) incorporating soil ionization and/or mutual coupling phenomena. As results, soil ionization generates a very slight decrease in potential values. This diminution is accentuated when considering mutual coupling phenomenon. A good accordance has been obtained when comparing our results to those reported by some researchers in the field.

Induced potential effect on pipelines nearby grounding systems

Abstract: This paper proposes a numerical method to calculate the induced potential and current in pipelines installed near a horizontal grounding electrode subjected to lightning discharge using the transmission line approach. The effect of this induced potential on the pipeline metal corrosion has been highlighted in term of mass loss for different soil resistivities and separation distances between pipeline and grounding system. Simulation results show that the induced potential is significant, indicating a serious problem for the pipe metal corrosion, especially for short separation distance between both systems and in more conductive soils. In such conditions, it is necessary to restrain the electromagnetic field by means of building insulating system between the grounding system and the pipelines.

Recurrent plot and quantification of leakage current for monitoring the insulator surface state under non-uniform desertic pollution

Abstract: This work is devoted to study the influence of the increasing of the width of the polluted band on insulators used in desert regions, by measuring the leakage current through the insulators surface. The Recurrent Plot technique (RP) is used to analyze the leakage current (LC) signal for monitoring the insulators surface state. This technique is applied directly on the leakage current waveforms, and the high frequency components are extracted from the leakage current signal using the wavelet transform technique. We also used the Recurrent Quantification Analysis (RQA) technique to quantify the RP characteristics of the LC signal and high frequency components, by computing the Recurrence Rate (RR), the Determinism (DET) and the Laminarity (LAM).