Publications Scientifiques
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Item Effect of shape factor on structural reliability analysis of a surface cracked pipeline-parametric study(2019) Guillal, Abdelkader; Abdelbaki, Noureddine; Bensghier, Mohamed El Amine; Betayeb, Mourad; Kopei, BogdanThe variation of crack shape factor (a/c) during propagation has an important role on calculation of the stress intensity factor (SIF), where imprecise estimation of this latter can lead us to an inaccurate prediction of failure probabilities. For the case of external cracked surface pipeline carried oil and gas products, such estimation can results undesired fault decisions like excessive repairs action or inspection planning. In this paper, the structural integrity analysis of pipeline with semi elliptical crack on the external surface is evaluated. Reliability calculations expressed in term of reliability index β are carried out based on Monte Carlo simulation and First Order reliability Method (FORM). The crack shape factors are varied to cover a variety of geometries from shallow to deep cracks while fatigue crack growth is assumed in depth direction. For SIF estimation, surface and deep point are considered. Results of the analysis indicate that for a constant crack depth a/t, the reliability index is strongly affected by a/c ratio and the trend is not similar in deep and surface point for different crack shapes.Item Contribution to The Reliability Study of Photovoltaic Systems Using Static and Dynamic Analysis Methods(Inderscience, 2019) Mahdi, Ismahan; Nadji, Bouchra; Simeu-Abazi, ZinebThe study of reliability has not been received great attention from researchers, an estimation of a lifetime and why not improve enhance is still possible. For that, it is necessary to distinguish the different failure modes, their causes and their effects on solar modules, in our case composed by Silicon, the most spread technology and the most used in the production of electricity. In this article, we will present a contribution to the reliability study of photovoltaic systems. First, the study will be focused on the static analysis of our system by using: structured analysis and design technique and function analysis system technique methods, which make it possible to carry out a functional analysis of our system. Next, our study will be based on the dynamic analysis by using: failure mode, effects, and criticality analysis, fault tree analysis and finally stochastic Petri nets methods. These allow making a dysfunctional analysis of the system by introducing the ‘time’ which is a very important factor in our studyItem Lifetime estimation and reliability of PV inverter with Multi-Timescale thermal stress analysis(IEEE, 2019) Bouguerra, Sara; Agroui, Kamel; Gassab, Oussama; Sangwongwanich, Ariya; Blaabjerg, FredeThe reliability of the PV inverter is a critical issue because it is the less reliable component of the PV system. In order to lower the risks of failure and maintenance in PV systems, the factors that influence the PV inverter lifetime should be analyzed. Thermal stress is the main causes of IGBT failure in a PV inverter, which includes the fast cycling stress due to loss variations in an IGBT, and slow cycling due to mission profile fluctuations. In this paper, the design for reliability (DFR) approach based on mission profile analysis is used and demonstrated on a single phase, single stage, grid connected PV inverter installed in Algeria, where the lifetime is estimated by taking the effect of low frequency thermal cycling under long-term operation into consideration, in addition to the line frequency power cycling due to loss variations. The results reveal that low frequency thermal cycling have a significant impact on lifetime degradation and reliability of the PV inverter after many years of operationItem Differential relay reliability enhancement using fourth harmonic for a large power transformer(Springer, 2017) Bouderbala, Rachid; Bentarzi, HamidA differential relay that is very sensitive relayoperating even at its limits may be used for protecting apower transformer. However, this characteristic may leadto unnecessary tripping due to transient currents such as aninrush and over excitation current. In order to avoid thismal-operation of the relay, a second and fifth harmonicblocking technique has been used; however this techniqueis not reliable if a second harmonic magnitude is weak. Inthis paper, a new approach is proposed using even har-monics (second and fourth). The test results show that thisproposed approach is a good blocking technique associatedwith the differential relay even for large modern powertransformer which has small second harmonic as well; itprovides a good discrimination between the transient cur-rents and the internal fault currents during internal fault.Item A New Frame Work for Protective Relay Tester(Inderscience, 2014) Chafai, Mahfoud; Bentarzi, Hamid; Ouadi, ABDERRAHMANE; Sahli, Hichem; Rial, HichemItem An embedded e-voting machine with smart card(Inderscience, 2016) Dichou, Karima; Tourtchine, Victor; Rahmoune, FaysalItem Distance relay reliability enhancement using false trip root cause analysis(Springer, 2017) Zitouni, Abdelkader; Ouadi, Abderrahmane; Bentarzi, Hamid; Chafai, MahfoudItem PC based testing system for protective relay(IEEE, 2013) Chafai, Mahfoud; Bentarzi, Hamid; Ouadi, Abderrahmane; Zitouni, Abdelkader; Recioui, AbdelmadjidItem A new PMU based power swing detector to enhance reliability of distance relay(2014) Bentarzi, Hamid; Ouadi, Abderrahmane; Maun, Jean ClaudePower grid protection aim is to make the generation, transmission and distribution of electrical energy as safe as possible from the effects of equipment failures. The operational security of the power system depends on the successful operation of the thousands of relays that protect power elements and hence protect the whole system against cascading failures. Thus, the failure of a relay to operate as intended may place at risk the entire power system and its elements. In conventional transmission line protection, a distance relay is used to provide the primary as well as backup protection. The voltage and current phasors measurement needed by the distance relay for determining the impedance may be affected by the power disturbances such as power swing. Consequently, this power swing may cause mal-operation of Zone three distance relays which in turn may affect on the reliability of the whole protective scheme. The mal-operation of this relay is generally due to not only unnecessary tripping during power swing that reduces the security of protection system and hence its reliability but also unnecessary blocking when symmetrical fault occurs accompanying a power swing. This latter action may affect on a dependability of the relay and hence its reliability. Many techniques have been developed to mitigate these effects and hence improve the relay reliability. One of the earliest techniques is the using of a negative sequence current magnitude and a derivative of current angle. This technique is very fast and its test results were promising in blocking false trip signals during power swing but when it is associated only with unsymmetrical faults. A combination of waveform of swing center’s voltage (WSCV) and synthetic negative vector has been also utilized to block the tripping signals during power swing. The technique seems to be rigorous indiscriminating power swing and high fault resistance. However, it requires two computationally heavy steps of derivative operation. There is also a time delay of about 30-40 ms before a power swing blocking scheme can be activated and hence the method is relatively slow. In order to improve the reliability of the relay, this work proposes a new scheme based on power swing detector using Phasor Measurement Units (PMUs). In addition to the local phasors information, the proposed scheme requires remote phasors information from different locations, which can be provided at high speed by PMUs. These measurements are used for calculating the power and the difference in phase voltages angles that may be used for detecting power swing and distinguishing it from the fault. This detector will not block relay when the power swing associated with any fault types. The MHO relay including power swing detector has been implemented using Simulink block set and S-function. To validate the present work, the performance of developed relay has been tested by signals generated by power network Simulink model running under different conditions. The test results show that this relay provides good discrimination between the transient high currents and the fault currentItem Large power transformer reliability modeling(Springer, 2016) Chafai, Mahfoud; Refoufi, Larbi; Bentarzi, Hamid