Study and Mitigation of AC Corrosion on Pipelines Nearby the HV Power Lines

HV power lines induce an AC, this latter causes corrosion damages on adjacent metallic structures. Therefore, the petroleum companies do confront serious corrosion problems of the underground pipelines nearby HV power lines, even where pipelines are protected by an insulation coating and the cathodic protection (CP). Therefore, we conducted a study, which we can summarise in three points. To begin with, we did a theoretical analysis to explain the fundamental mechanisms of AC corrosion. Afterwards, we did an experimental investigation on a laboratory model, to realise electrochemical tests on a pipeline steel sample. Then, as we found that the AC corrosion numerical simulation study is minimal in the electrochemical and the electrical fields, we did further numerical simulation studies. This latter contains the study of the electrochemical reactions of the corrosion phenomena such as anodic process and cathodic process; i.e. the iron oxidation and the reduction of both the oxygen and the hydrogen. We have also simulated the CP, the AC corrosion and the pipeline sample deformation. At last, to solve this problem, we developed a monitoring and correction program for optimising the AC corrosion. In this article, we represented the obtained experimental and numerical simulation results. In addition, we want also to mention the original and personal added values in both studies

Application des fonctions Kernels de la méthode LS-SVM pour le diagnostic d’un isolateur HT pollué

This work presents a method to predict the polluted level of the surfaces of an insulator, that is to say, to diagnose the operational conditions of the isolation of an electrical system by pattern recognition techniques using some types of methods such as Least square support vectors machines (LS-SVM); we present here several kernel functions like RBF, polykernel and MLP. The methodology is to use as input variables of the insulation such as diameter, height, creepage line, form factor and equivalent salt deposition density. The majority of the variables to be predicted are dependent on several independent variables. The results of this work are useful in predicting the severity of contamination, the critical overvoltage; arc length and especially affects the overvoltage. The validity of the approach was examined by testing several insulators with different geometries. Field experience and laboratory tests are expensive both in time and money; therefore this method takes efficiency vs experimental tests in laboratories. A comparison of the kernel functions used shows the improvement of LS-SVM with RBF, Polykernels and that the use of combined models is a powerful technique for this type of application demand

Effect of the dielectric inhomogeneity factor's range on the electrical tree evolution in solid dielectrics

The main contribution of the presented paper is to investigate the influence of the Dielectric Inhomogeneity Factor on the electrical tree evolution in solid dielectrics using cellular automata. We have a sample of the XLPE which is located between needle-to-plane electrodes under DC voltage. The electrical tree emanates from the end of the needle in which the electric stress attains a dielectric strength of the material. At every time step, Laplace's equation is solved to calculate the potential distribution which changes according to electrical tree development. Dynamic simulations clearly demonstrate the influence of the range of the Dielectric Inhomogeneity Factor on the electrical tree growth. Simulation results confirm the published technical literature

The impact of layout and concentration of defects on the electromechanical constraints in the MV cables insulation

The problem of the dense presence of voids in the solid insulation of cables remains a concern for researchers in terms of diagnosis and maintenance. The focus of this paper is to investigate the influence of both the layout and density of microcavities on the electrical and electromechanical constraints in the XLPE insulation of MV cables using numerical simulation. The simulation is based on the resolution of Laplace’s equation by the finite element method (FEM) using MATLAB. The electrostatic pressure and the elongation of the microcavities are estimated. This elongation leads to the formation of microchannels and then develops due to partial discharges to arborescence and in the end, the cable becomes out of service. This process takes a long time, so we use simulations to deepen the understanding of this phenomenon in a very short time. The electromechanical constraints are determined for different layouts and densities of microcavities

The impact of layout and concentration of defects on the electromechanical constraints in the MV cables insulation

The problem of the dense presence of voids in the solid insulation of cables remains a concern for researchers in terms of diagnosis and maintenance. The focus of this paper is to investigate the influence of both the layout and density of microcavities on the electrical and electromechanical constraints in the XLPE insulation of MV cables using numerical simulation. The simulation is based on the resolution of Laplace’s equation by the finite element method (FEM) using MATLAB. The electrostatic pressure and the elongation of the microcavities are estimated. This elongation leads to the formation of microchannels and then develops due to partial discharges to arborescence and in the end, the cable becomes out of service. This process takes a long time, so we use simulations to deepen the understanding of this phenomenon in a very short time. The electromechanical constraints are determined for different layouts and densities of microcavities

Prediction of critical flashover voltage of polluted insulators under sec and rain conditions using least squares support vector machines (LS-SVM)

This paper describes a methodology that was developed for the prediction of the critical flashover voltage of polluted insulators under sec and rain conditions least squares support vector machines (LS-SVM) optimization. The methodology uses as input variable characteristics of the insulator such as diameter, height, creepage distance, and the number of elements on a chain of insulators. The estimation of the flashover performance of polluted insulators is based on field experience and laboratory tests are invaluable as they significantly reduce the time and labour involved in insulator design and selection. The majority of the variables to be predicted are dependent upon several independent variables. The results from this work are useful to predict the contamination severity, critical flashover voltage as a function of contamination severity, arc length, and especially to predict the flashover voltage. The validity of the approach was examined by testing several insulators with different geometries. A comparison with the Grouping Multi-Duolateration Localization (GMDL) method proves the accuracy and goodness of LS-SVM. Moreover LS-SVMs give a good estimation of results which are validated by experimental tests

The influence of Crystallization and Morphology on the Field Mechanical Induced Strain of Poly(Ethylene 2,6-Naphthalene Dicarboxylate) Thin Films

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Feedback Linearization Control for Highly Uncertain Nonlinear Systems Augmented by Single-Hidden-Layer Neural Networks

The main objective of this paper is to design an adaptive output feedback control for a class of uncertain nonlinear systems using only one Single-Hidden-Layer (SHL) Neural Networks (NN) in order to eliminate the unstructured uncertainties. The approach employs feedback linearization, coupled with an on-line NN to compensate for modelling errors. A fixed structure dynamic compensator is designed to stabilize the linearized system. A signal, comprised of a linear combination of the measured tracking error and the compensator states, is used to adapt the NN weights. The network weight adaptation rule is derived from Lyapunov stability analysis, and guarantees that the adapted weight errors and the tracking error are bounded. Numerical simulations of both nonlinear systems, Van der Pol example and tunnel diode circuit model, having full relative degree, are used to illustrate the practical potential of the proposed approach