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Abderrahmane Beroual - One of the best experts on this subject based on the ideXlab platform.

  • Pre-breakdown mechanisms in dielectric liquids and predicting models
    2016 IEEE Electrical Insulation Conference (EIC), 2016
    Co-Authors: Abderrahmane Beroual
    Abstract:

    This paper presents a synthetic review of the state of knowledge relative to the pre-breakdown phenomena in dielectric liquids and especially the initiation and propagation of streamer/discharge and their characteristic parameters. The main influencing parameters namely the structure, stopping length, velocity and propagation modes of streamers, current, charge and associated emitted light are developed. These parameters include especially the chemical composition of the liquid (pure or containing specific additives); the applied voltage; the electrode arrangement; the temperature and the hydrostatic pressure. The mechanisms involving in the inception and propagation of streamers are discussed. Recent models enabling to predict the type of streamers that can be initiated and their characteristics when propagating within liquid, are also presented and discussed. It is shown through the experiments and modeling that the pre-breakdown phenomena in dielectric liquids are governed by both electronic and gaseous mechanisms even if one of them is dominant in one case and the second in another.

  • Pre-breakdown and breakdown Currents and correlated light emissions analysis in liquid dielectrics
    2015
    Co-Authors: S. Sahra, Bachir Lehouidj, Y. Hadji, Azzedine Nacer, Hocine Moulai, Abderrahmane Beroual
    Abstract:

    Condition monitoring and fault diagnostics plays a very important role in the production security and the product quality. The demand for monitoring and fault diagnosis of power systems has increased the efforts to develop new analysis techniques. A wide variety of techniques were used for this purpose. In this work, a systematic survey on positive and negative streamers currents and corresponding emitted lights has been led in three liquid dielectrics: Mineral oil, tetraester and toluene, and the results are presented and discussed with regard to their energy and frequency parameters.This study will mainly investigate real time techniques for signal identification of electrical discharges of different energy levels mainly in transformer mineral oil in order to identify the Steamers propagation that can transit to high level energy arcing discharges. The energy and inter-correlation between electrical and light signals are also investigated. The use of artificial neural networks (ANN) for real time discharge signals analysis (currents or/and emitted lights) has been proved to be a fast and reliable solution for the protection of sensitive power equipments. With a database of 40 samples of each type of signal used for training the ANN, acceptable results with a rate of 75% of success have been obtained.

  • Streamers Optical and Electrical Characteristics Correlations in Liquid Dielectrics Under Alternating Current Stress
    Plasma Chemistry and Plasma Processing, 2014
    Co-Authors: Hocine Moulai, Azzedine Nacer, Abderrahmane Beroual
    Abstract:

    This paper is devoted to the analysis of optical and electrical characteristics of positive streamers (namely the emitted light and current signals, electric field, velocity and electrical charge) propagating in mineral oil, tetra-ester and toluene, in a point-plane electrode arrangement, under alternating current voltage. Correlations are established between the different characteristics of streamers especially between the velocity and the current derivative indicating that the streamers present also a certain inductive nature, contrarily to the generally used assumptions where streamers propagating are considered of only resistive and capacitive nature. The frequency spectra of the current pulses are also investigated and enlighten all similarities and differences between the studied oils. Each type of discharge can be well identified in relation with the nature of the liquid by the analysis of the frequency behaviour of the corresponding currents or emitted lights. The behaviour of each current streamer is found to be highly influenced by the liquid temperature of evaporation and its electronic affinity.

  • Correlation between current, emitted light, electric field and propagation velocity of positive streamers in liquid dielectrics under AC voltage
    2011 IEEE International Conference on Dielectric Liquids, 2011
    Co-Authors: Hocine Moulai, Azzedine Nacer, Abderrahmane Beroual
    Abstract:

    The paper reports on the search of correlations between the current and emitted light signal, electric field, and propagation velocity associated to positive streamers propagating in mineral oil, tetra-ester and toluene, in a point - plane electrode arrangement, under AC voltage. New correlations, especially between the velocity of positive streamers and the current derivative are established. The frequency spectra of different current pulses and emitted lights are also presented.

  • electronic and gaseous processes in the prebreakdown phenomena of dielectric liquids
    Journal of Applied Physics, 1993
    Co-Authors: Abderrahmane Beroual
    Abstract:

    The article shows experimentally the simultaneous influence of electronic scavenger additives and the hydrostatic pressure on the current and emitted light by streamers, especially in cyclohexane under negative polarity. This suggests that both electronic and gaseous mechanisms do not act singly in the prebreakdown phase of dielectric liquids. A relationship between the streamer current, the electrical charge, the velocity, and the propagation mode of streamers is discussed. Based on energy considerations, we establish a mathematical expression allowing us to evaluate the velocity of streamers and to explain the propagation modes. The streamer the current of which consists of discrete pulses moves by steps. The higher the number and/or the amplitude of the current pulses, the shorter the durations between these steps and the higher the average velocity of the streamers; its propagation tends to become continuous. That is the case of the slow streamers in the presence of electronic scavenger additives. On the other hand, the streamer becomes rapid then more energetic and the hydrostatic pressure necessary for its disappearance increases. That is why it is thought that both gaseous and electronic processes simultaneously act in the prebreakdown phase even if one of them is dominant in one case and the second in another.

Azzedine Nacer - One of the best experts on this subject based on the ideXlab platform.

  • Pre-breakdown and breakdown Currents and correlated light emissions analysis in liquid dielectrics
    2015
    Co-Authors: S. Sahra, Bachir Lehouidj, Y. Hadji, Azzedine Nacer, Hocine Moulai, Abderrahmane Beroual
    Abstract:

    Condition monitoring and fault diagnostics plays a very important role in the production security and the product quality. The demand for monitoring and fault diagnosis of power systems has increased the efforts to develop new analysis techniques. A wide variety of techniques were used for this purpose. In this work, a systematic survey on positive and negative streamers currents and corresponding emitted lights has been led in three liquid dielectrics: Mineral oil, tetraester and toluene, and the results are presented and discussed with regard to their energy and frequency parameters.This study will mainly investigate real time techniques for signal identification of electrical discharges of different energy levels mainly in transformer mineral oil in order to identify the Steamers propagation that can transit to high level energy arcing discharges. The energy and inter-correlation between electrical and light signals are also investigated. The use of artificial neural networks (ANN) for real time discharge signals analysis (currents or/and emitted lights) has been proved to be a fast and reliable solution for the protection of sensitive power equipments. With a database of 40 samples of each type of signal used for training the ANN, acceptable results with a rate of 75% of success have been obtained.

  • Streamers Optical and Electrical Characteristics Correlations in Liquid Dielectrics Under Alternating Current Stress
    Plasma Chemistry and Plasma Processing, 2014
    Co-Authors: Hocine Moulai, Azzedine Nacer, Abderrahmane Beroual
    Abstract:

    This paper is devoted to the analysis of optical and electrical characteristics of positive streamers (namely the emitted light and current signals, electric field, velocity and electrical charge) propagating in mineral oil, tetra-ester and toluene, in a point-plane electrode arrangement, under alternating current voltage. Correlations are established between the different characteristics of streamers especially between the velocity and the current derivative indicating that the streamers present also a certain inductive nature, contrarily to the generally used assumptions where streamers propagating are considered of only resistive and capacitive nature. The frequency spectra of the current pulses are also investigated and enlighten all similarities and differences between the studied oils. Each type of discharge can be well identified in relation with the nature of the liquid by the analysis of the frequency behaviour of the corresponding currents or emitted lights. The behaviour of each current streamer is found to be highly influenced by the liquid temperature of evaporation and its electronic affinity.

  • Correlation between current, emitted light, electric field and propagation velocity of positive streamers in liquid dielectrics under AC voltage
    2011 IEEE International Conference on Dielectric Liquids, 2011
    Co-Authors: Hocine Moulai, Azzedine Nacer, Abderrahmane Beroual
    Abstract:

    The paper reports on the search of correlations between the current and emitted light signal, electric field, and propagation velocity associated to positive streamers propagating in mineral oil, tetra-ester and toluene, in a point - plane electrode arrangement, under AC voltage. New correlations, especially between the velocity of positive streamers and the current derivative are established. The frequency spectra of different current pulses and emitted lights are also presented.

Hocine Moulai - One of the best experts on this subject based on the ideXlab platform.

  • Pre-breakdown and breakdown Currents and correlated light emissions analysis in liquid dielectrics
    2015
    Co-Authors: S. Sahra, Bachir Lehouidj, Y. Hadji, Azzedine Nacer, Hocine Moulai, Abderrahmane Beroual
    Abstract:

    Condition monitoring and fault diagnostics plays a very important role in the production security and the product quality. The demand for monitoring and fault diagnosis of power systems has increased the efforts to develop new analysis techniques. A wide variety of techniques were used for this purpose. In this work, a systematic survey on positive and negative streamers currents and corresponding emitted lights has been led in three liquid dielectrics: Mineral oil, tetraester and toluene, and the results are presented and discussed with regard to their energy and frequency parameters.This study will mainly investigate real time techniques for signal identification of electrical discharges of different energy levels mainly in transformer mineral oil in order to identify the Steamers propagation that can transit to high level energy arcing discharges. The energy and inter-correlation between electrical and light signals are also investigated. The use of artificial neural networks (ANN) for real time discharge signals analysis (currents or/and emitted lights) has been proved to be a fast and reliable solution for the protection of sensitive power equipments. With a database of 40 samples of each type of signal used for training the ANN, acceptable results with a rate of 75% of success have been obtained.

  • Streamers Optical and Electrical Characteristics Correlations in Liquid Dielectrics Under Alternating Current Stress
    Plasma Chemistry and Plasma Processing, 2014
    Co-Authors: Hocine Moulai, Azzedine Nacer, Abderrahmane Beroual
    Abstract:

    This paper is devoted to the analysis of optical and electrical characteristics of positive streamers (namely the emitted light and current signals, electric field, velocity and electrical charge) propagating in mineral oil, tetra-ester and toluene, in a point-plane electrode arrangement, under alternating current voltage. Correlations are established between the different characteristics of streamers especially between the velocity and the current derivative indicating that the streamers present also a certain inductive nature, contrarily to the generally used assumptions where streamers propagating are considered of only resistive and capacitive nature. The frequency spectra of the current pulses are also investigated and enlighten all similarities and differences between the studied oils. Each type of discharge can be well identified in relation with the nature of the liquid by the analysis of the frequency behaviour of the corresponding currents or emitted lights. The behaviour of each current streamer is found to be highly influenced by the liquid temperature of evaporation and its electronic affinity.

  • Correlation between current, emitted light, electric field and propagation velocity of positive streamers in liquid dielectrics under AC voltage
    2011 IEEE International Conference on Dielectric Liquids, 2011
    Co-Authors: Hocine Moulai, Azzedine Nacer, Abderrahmane Beroual
    Abstract:

    The paper reports on the search of correlations between the current and emitted light signal, electric field, and propagation velocity associated to positive streamers propagating in mineral oil, tetra-ester and toluene, in a point - plane electrode arrangement, under AC voltage. New correlations, especially between the velocity of positive streamers and the current derivative are established. The frequency spectra of different current pulses and emitted lights are also presented.

Jaunez A. - One of the best experts on this subject based on the ideXlab platform.

Ute Ebert - One of the best experts on this subject based on the ideXlab platform.

  • positive and negative streamers in ambient air measuring diameter velocity and dissipated energy
    Journal of Physics D, 2008
    Co-Authors: Tmp Tanja Briels, J Kos, Gjj Hans Winands, Van Em Eddie Veldhuizen, Ute Ebert
    Abstract:

    Positive and negative streamers are studied in ambient air at 1 bar; they emerge from a needle electrode placed 40 mm above a planar electrode. The amplitudes of the applied voltage pulses range from 5 to 96 kV; most pulses have rise times of 30 ns or shorter. Diameters, velocities and energies of the streamers are measured. Two regimes are identified; a low voltage regime where only positive streamers appear and a high voltage regime where both positive and negative streamers exist. Below 5 kV, no streamers emerge. In the range from 5 to 40 kV, positive streamers form, while the negative discharges only form a glowing cloud at the electrode tip, but no streamers. For 5–20 kV, diameters and velocities of the positive streamers have the minimal values of d = 0.2 mm and v ≈ 105 m s−1. For 20–40 kV, their diameters increase by a factor of 6 while the voltage increases only by a factor of 2. Above the transition value of 40 kV, streamers of both polarities form; they strongly resemble each other, though the positive ones propagate further; their diameters continue to increase with applied voltage. For 96 kV, positive streamers attain diameters of 3 mm and velocities of 4 × 106 m s−1; negative streamers are about 20% slower and thinner. An empirical fit formula for the relation between velocity v and diameter d is v = 0.5d2 mm−1 ns−1 for both polarities. Streamers of both polarities dissipate energies of the order of several millijoules per streamer while crossing the gap.

  • positive and negative streamers in ambient air measuring diameter velocity and dissipated energy
    arXiv: Plasma Physics, 2008
    Co-Authors: Tmp Tanja Briels, J Kos, Gjj Hans Winands, Van Em Eddie Veldhuizen, Ute Ebert
    Abstract:

    Positive and negative streamers are studied in ambient air at 1 bar; they emerge from a needle electrode placed 40 mm above a planar electrode. The amplitudes of the applied voltage pulses range from 5 to 96 kV; most pulses have rise times of 30 ns or shorter. Diameters, velocities and energies of the streamers are measured. Two regimes are identified; a low voltage regime where only positive streamers appear and a high voltage regime where both positive and negative streamers exist. Below 5 kV, no streamers emerge. In the range from 5 to 40 kV, positive streamers form, while the negative discharges only form a glowing cloud at the electrode tip, but no streamers. For 5 to 20 kV, diameters and velocities of the positive streamers have the minimal values of d=0.2 mm and v \approx 10^5 m/s. For 20 to 40 kV, their diameters increase by a factor 6 while the voltage increases only by a factor 2. Above the transition value of 40 kV, streamers of both polarities form; they strongly resemble each other, though the positive ones propagate further; their diameters continue to increase with applied voltage. For 96 kV, positive streamers attain diameters of 3 mm and velocities of 4*10^6 m/s, negative streamers are about 20 % slower and thinner. An empirical fit formula for the relation between velocity v and diameter d is v=0.5 d^2/(mm ns) for both polarities. Streamers of both polarities dissipate energies of the order of several mJ per streamer while crossing the gap.