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  • 1.
    Arapan, Lilia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Alexieva, Gergana
    Dept of Solid State Physics and Microelectronics, University of Sofia, Bulgarien.
    Avramov, Ivan D
    Georgy nadjakov Institute of Solid State Physics, Sofia,Bulgarian Academy of Sciences.
    Radeva, Elisaveta
    Georgy Nadjakov Institute of Solid State Physics, Sofia, Bulgarian Academy of Sciences.
    Strashilov, Vesseline
    University of Sofia.
    Katardjiev, Ilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Yantchev, Ventsislav
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Highly Mass-Sensitive Thin Film Plate Acoustic Resonators (FPAR)2011In: Sensors, E-ISSN 1424-8220, Vol. 11, no 7, p. 6942-6953Article in journal (Refereed)
    Abstract [en]

    The mass sensitivity of thin aluminum nitride (AlN) film S0 Lamb wave resonators is theoretically and experimentally studied. Theoretical predictions based on modal and finite elements method analysis are experimentally verified. Here, two-port 888 MHz synchronous FPARs are micromachined and subsequently coated with hexamethyl-disiloxane(HMDSO)-plasma-polymerized thin films of various thicknesses. Systematic data on frequency shift and insertion loss versus film thickness are presented. FPARs demonstrate high mass-loading sensitivity as well as good tolerance towards the HMDSO viscous losses. Initial measurements in gas phase environment are further presented.

    Download full text (pdf)
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  • 2.
    Arapan, Lilia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Avramov, Ivan
    Inst Solid State Physics, Bulgarian Academy of Sciences.
    Yantchev, Ventsislav
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Thin film plate acoustic resonators for integrated microwave power oscillator applications2011In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 47, no 7, p. 452-453Article in journal (Refereed)
    Abstract [en]

    Two-port film plate acoustic resonators (FPAR) devices operating on the lowest order symmetric Lamb wave mode (S0) in C-oriented AlN membranes on Si were fabricated and tested for their power handling capabilities in a feedback-loop power oscillator circuit. The FPAR was operated at an incident power level of 24 dBm for several weeks without performance degradation. Its flicker noise constant was calculated from close-in phase noise data as αR=2.1×10^−36/Hz. The results indicate that IC-compatible S0 FPARs are well suited for integrated microwave oscillators with thermal noise floor (TNF) levels below −175 dBc/Hz.

  • 3. Arevalo, L.
    et al.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Corona charge produced by thundercloud fields in grounded rods2012In: 31st International Conference on Lightning Protection ICLP 2012, 2012, p. 6344365-Conference paper (Refereed)
    Abstract [en]

    Electrostatic fields below the thundercloud lead to the formation of glow charge from grounded objects. The charge accumulated after certain time can initiate or inhibit the called streamer formation and consequently the inception and development of upward leaders. By means of a two dimensional numerical model that takes into account the particles behavior is observed that glow charge can smooth the electric field on top of the grounded rod and consequently hinder the inception of streamers and upward leaders from the grounded rod. It is concluded that to be able to initiate unstable upward leaders from the shielded grounded rod a sudden change of electric field is necessary. A two dimensional numerical model that solves the continuity equations for positive and negative ions and electrons coupled with Poisson equation was implemented. Comparison for different magnitudes of electric field and characteristics of rod are included as well.

  • 4.
    Arevalo, Liliana
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Numerical Simulations of Long Spark and Lightning Attachment2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The research work presented here is concerned with numerical simulations of two different electrical phenomena: Long gap electrical discharges under switching impulses and the lightning attachment process associated with positive upward leaders. The development of positive upward leaders and the progression of discharges in long gaps are attributable to two intertwined physical phenomena, namely, the leader channel and the streamer zone. The physical description and the proposed calculations of the above-mentioned phenomena are based on experimental tests conducted in long spark gaps.

    The methodology presented here proposes a new geometrical approximation for the representation of the streamer and the calculation of the accumulated electrical charge. Furthermore, two different approaches to representing the leader channel are applied and compared. Statistical delays before the inception of the first corona, and random distributions to represent the tortuous nature of the path taken by the leader channel were included based on the behavior observed in experimental tests, with the intention of ensuring the discharge behaved in a realistic manner. A reasonable agreement was found between the physical model and the experimental test results.

    A model is proposed to simulate the negative discharges produced by switching impulses using the methodology developed to simulate positive leader discharges and the physics underlying the negative leader phenomena. The validation of the method demonstrated that phenomena such as the pilot leader and negative leader currents are successfully represented.

    In addition, based on previous work conducted on the physics of lightning and the lightning attachment process, a new methodology is developed and tested. In this new approach, the background electric field and the ionized region, considered in conjunction with the advance of the leader segment, are computed using a novel method. The proposed methodology was employed to test two engineering methods that are accepted in international standards, the mesh method and the electro-geometrical method. The results demonstrated that the engineering approximations are consistent with the physical approach.

    In addition to the electrical phenomena mentioned above, one should remember that, to simplify the calculation, there are certain real effects arising from the lightning attachment process that have not been considered. In fact, when a structure is subjected to a strong electric field, it is possible to generate multiple upward leaders from that structure. This effect has not been taken into account in the numerical models available previously, and therefore the process of generating multiple upward leaders incepted over a structure is incorporated here. The results have shown that a slight advantage from the background electric field is enough for one upward connecting leader to take over, thereby forcing the others to abort the attachment process.

    List of papers
    1. Modelling of Positive Discharges in Laboratory Gaps under Switching impulses
    Open this publication in new window or tab >>Modelling of Positive Discharges in Laboratory Gaps under Switching impulses
    2008 (English)Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    Cardiff, UK: , 2008
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-113403 (URN)
    Conference
    XVII International Conference on Gas Discharges and Their applications
    Available from: 2010-01-28 Created: 2010-01-28 Last updated: 2016-04-12Bibliographically approved
    2. Breakdown effect on long gaps under switching impulses statistical variation
    Open this publication in new window or tab >>Breakdown effect on long gaps under switching impulses statistical variation
    2008 (English)Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    Uppsala, Sweden: , 2008
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-113402 (URN)
    Conference
    29th International Conference on Lightning Protection
    Available from: 2010-01-28 Created: 2010-01-28 Last updated: 2016-04-12Bibliographically approved
    3. Breakdown times and voltages probability calculation using a simplified numerical methodology
    Open this publication in new window or tab >>Breakdown times and voltages probability calculation using a simplified numerical methodology
    2008 (English)Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    Florianopolis Brazil: , 2008
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-113401 (URN)
    Conference
    International Conference on Grounding and Earthing and 3rd International Conference on Lightning Physics and Effects
    Available from: 2010-01-28 Created: 2010-01-28 Last updated: 2016-04-12Bibliographically approved
    4. Numerical simulation of long laboratory sparks generated by positive switching impulses
    Open this publication in new window or tab >>Numerical simulation of long laboratory sparks generated by positive switching impulses
    2009 (English)In: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 67, no 2-3, p. 228-234Article in journal (Refereed) Published
    Abstract [en]

    A numerical methodology using two different leader channel criteria has been implemented. The methodology is based on Bondiou and Gallimberti's proposition [A. Bondiou, I. Gallimberti, Theoretical modelling of the development of the positive spark in long spark, J. Phys. D: Appl. Phys. 27 (1994) 1252-1266]. The leader channel criteria used are Rizk engineering criterion [Rizk, A model for switching impulse leader inception and breakdown of long air gaps, IEEE Trans. Power Deliv., 4(1) (1989)] and Local thermodynamic - L.T.E. - physical concept [I. Gallimberti, The mechanism of the long spark formation, Colloque C7, J. Phys. (supplement au nro 7, Tome 40) (July 1979) C7-193]. The methodology was tested in three different cases; a deterministic case, a statistical variation and a typical constant level test. Deterministic calculation considered corona inception using stabilization corona electric field criterion of Gallimberti [I. Gallimberti, The mechanism of the long spark formation, Colloque C7, J. Phys. (supplement au nro 7, Tome 40) (July 1979) C7-193] and the leader moving as segments. The statistical simulation has two different statistical delays, one at inception and the other due to the tortuous characteristics of the leader channel. The constant level test consists of 200 positive switching impulses with the same characteristics such as maximum applied voltage, time to crest and time to fall. Time to breakdown and breakdown voltage were found based on the results obtained from the constant level test characteristics. All the numerical results presented are based on experimental conditions reported in [Les Renardières Group, Research on long gap discharges at Les Renardières, Electra N 35 (1973)] from the world class research group namely Les Renardieres Group.

    Keywords
    Discharge, Leader, Modeling, Switching
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-113133 (URN)10.1016/j.elstat.2008.12.022 (DOI)000266019500029 ()0304-3886 (ISBN)
    Available from: 2010-01-25 Created: 2010-01-25 Last updated: 2017-12-12Bibliographically approved
    5. LABORATORY LONG GAPS SIMULATION CONSIDERING A VARIABLE CORONA REGION
    Open this publication in new window or tab >>LABORATORY LONG GAPS SIMULATION CONSIDERING A VARIABLE CORONA REGION
    2010 (English)Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    Cagliary, Italy: , 2010
    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-140390 (URN)
    Conference
    30TH International Conference on Lightning Protection, ICLP
    Available from: 2011-01-05 Created: 2011-01-05 Last updated: 2016-03-03
    6. A RELIABLE NUMERICAL METHOD FOR THE CALCULATION OF BREAKDOWN VOLTAGES
    Open this publication in new window or tab >>A RELIABLE NUMERICAL METHOD FOR THE CALCULATION OF BREAKDOWN VOLTAGES
    2010 (English)Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    Cagliary, Italy: , 2010
    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-140391 (URN)
    Conference
    30TH International Conference on Lightning Protection, ICLP
    Available from: 2011-01-05 Created: 2011-01-05 Last updated: 2014-12-10
    7. A new static calculation of the streamer region for long spark gaps
    Open this publication in new window or tab >>A new static calculation of the streamer region for long spark gaps
    2012 (English)In: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 70, no 1, p. 15-19Article in journal (Refereed) Published
    Abstract [en]

    Different electrostatic approximations have been proposed to calculate the streamer region without going in deep details of the behavior of density of particles under the effect of high electric fields; this kind of approximations have been used in numerical calculations of long spark gaps and lightning attachment. The simplifications of the streamer region are achieved by considering it to be a geometrical region with a constant geometrical shape. Different geometrical shapes have been used, such as cones or several parallel filaments. Afterward, to simplify the procedures, the streamer region was approximated by two constants, one denoted K-Q, called the geometrical constant and in other cases K named as geometrical factor. However, when a voltage that varies with time is applied to an arrangement of electrodes (high voltage and grounded electrodes), the background electric field will change with time. Thus, if the background electric field is modified, the streamer zone could cover a larger or smaller area. With the aim of reducing the number of assumptions required in the calculation of long gap discharges, a new electrostatic model to calculate the streamer region is presented. This model considers a variable streamer zone that changes with the electric field variations. The three-dimensional region that fulfills the minimum electric field to sustain a streamer is identified for each time step, and the charge accumulated in that region is then calculated. The only parameter that is being used in the calculation is the minimum electric field necessary for the propagation of streamers.

    Keywords
    charge, leader, Streamer, Electrical charge, Electric field, Corona inception, Discharge
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Electricity, Esp The Study Of Transients and Discharges; Engineering Science with specialization in Science of Electricity
    Identifiers
    urn:nbn:se:uu:diva-150528 (URN)10.1016/j.elstat.2011.07.013 (DOI)000300804300003 ()
    Available from: 2011-03-31 Created: 2011-03-31 Last updated: 2017-12-11Bibliographically approved
    8. The development of long spark gaps: Simulation including a variable streamer region
    Open this publication in new window or tab >>The development of long spark gaps: Simulation including a variable streamer region
    (English)Article in journal (Refereed) Submitted
    Keywords
    Breakdown, streamer, discharge
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-150531 (URN)
    Available from: 2011-03-31 Created: 2011-03-31 Last updated: 2016-03-03
    9. Reliable model for the calculation of negative leader discharges under switching impulses
    Open this publication in new window or tab >>Reliable model for the calculation of negative leader discharges under switching impulses
    2010 (English)Conference paper, Published paper (Refereed)
    Keywords
    negative streamer, space leader, breakdown
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-150533 (URN)
    Conference
    36th grounding and 4th Lightning Physics conference GND&LPE
    Available from: 2011-03-31 Created: 2011-03-31 Last updated: 2016-04-18
    10. A preliminary model to simulate negative leader discharges
    Open this publication in new window or tab >>A preliminary model to simulate negative leader discharges
    (English)In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463Article in journal (Refereed) Submitted
    Keywords
    Negative streamer, pilot system, breakdown
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-150532 (URN)
    Available from: 2011-03-31 Created: 2011-03-31 Last updated: 2017-12-11
    11. On the interception of lightning flashes by power transmission lines
    Open this publication in new window or tab >>On the interception of lightning flashes by power transmission lines
    2011 (English)In: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 69, no 3, p. 220-227Article in journal (Refereed) Published
    Abstract [en]

    The design of the lightning protection system LPS of transmission lines is based on the well knownelectro-geometrical model. The electro-geometrical model assumes that the first point on a powertransmission line that will come within striking distance of the tip of a down-coming stepped leaderchannel is the strike point of the lightning flash. The model neglects almost all of the physics associatedwith the lightning attachment.Nowadays, as it is possible to use modern hardware and software tools and several different numericalmethods, it is feasible to apply the physics of the discharge process to the study of lightning attachment.Such models take into account the movement of the downward and the resulting upward leaders fromdifferent points on the structures under consideration.In this paper, a procedure based on lightning physics was used to analyze the lightning attachmentphenomena in EHV transmission lines of 230 kV and 500 kV and the results were compared with thepredictions of the electro-geometrical method.

    Keywords
    power system, lightning attachment, breakdown, downward leader
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-150534 (URN)10.1016/j.elstat.2011.03.013 (DOI)000292230300012 ()
    Available from: 2011-03-31 Created: 2011-03-31 Last updated: 2017-12-11
    12. 'The mesh method' in lightning protection standards - Revisited
    Open this publication in new window or tab >>'The mesh method' in lightning protection standards - Revisited
    2010 (English)In: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 68, no 4, p. 311-314Article in journal (Refereed) Published
    Abstract [en]

    At present the design of the Lightning protection systems (LPS) for structures as stipulated in standards is based on the electro - geometrical method, which was initially used to protect power lines from lightning. A derivative of the electro-geometrical method is the rolling sphere method. This method together, with the protection angle method and mesh method are used almost in all lightning standards as the measure in installing the lightning protection systems of grounded structures. In the mesh method, the dimension of the cell size in different levels of protection is determined using the rolling sphere method. Since the rolling sphere method does not take into account the physics of the lightning attachment process there is a need to evaluate the validity of the stipulated value in standards of the minimum lightning current that can penetrate through the mesh in different levels of protection. In this paper, meshes of different sizes as stipulated in the lightning protection standards were tested for their ability to intercept lightning flashes using a lightning attachment model that takes into account the physics of connecting leaders on. The results are in reasonable agreement with the specifications given in the lightning protection standards.

    Keywords
    Dynamic leader, Electro-geometrical method, Lightning inception, Mesh method, Upward leader, Standards
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-135183 (URN)10.1016/j.elstat.2010.03.003 (DOI)000281211700004 ()
    Available from: 2010-12-06 Created: 2010-12-06 Last updated: 2017-12-12Bibliographically approved
    13. Influence of multiple upward connecting leaders initiated from the same structure on the lightning attachment process
    Open this publication in new window or tab >>Influence of multiple upward connecting leaders initiated from the same structure on the lightning attachment process
    2009 (English)Conference paper, Published paper (Refereed)
    Keywords
    electric field, inhibit discharge, breakdown, streamer, lightning, attachment
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-150535 (URN)
    Conference
    X International symposium on lightning protection - SIPDA
    Available from: 2011-03-31 Created: 2011-03-31 Last updated: 2016-04-14
    14. Interaction of multiple connecting leaders issued from a grounded structure simulated using a self consistent leader inception and propagation model SLIM
    Open this publication in new window or tab >>Interaction of multiple connecting leaders issued from a grounded structure simulated using a self consistent leader inception and propagation model SLIM
    2010 (English)In: 30TH International Conference on Lightning Protection, ICLP, Cagliary, Italy, 2010Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    Cagliary, Italy: , 2010
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-142452 (URN)
    Conference
    30TH International Conference on Lightning Protection, ICLP
    Available from: 2011-01-14 Created: 2011-01-14 Last updated: 2022-01-28Bibliographically approved
    Download full text (pdf)
    FULLTEXT01
  • 5.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. elektricitetslära och åskforskning.
    Becerra, Marley
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. elektricitetslära och åskforskning.
    Roman, F
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. elektricitetslära och åskforskning.
    Understanding the point discharge DC current produced by corona needles2006In: Proceedings of the 28th Internat Conference on Lightning Protection, ICLP, Kanazawa, Japan, 2006, p. 1328-1333Conference paper (Refereed)
  • 6.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    A preliminary model to simulate negative leader dischargesIn: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463Article in journal (Refereed)
  • 7.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    A RELIABLE NUMERICAL METHOD FOR THE CALCULATION OF BREAKDOWN VOLTAGES2010Conference paper (Refereed)
  • 8.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Influence of multiple upward connecting leaders initiated from the same structure on the lightning attachment process2009Conference paper (Refereed)
  • 9.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    LABORATORY LONG GAPS SIMULATION CONSIDERING A VARIABLE CORONA REGION2010Conference paper (Refereed)
  • 10.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    On the interception of lightning flashes by power transmission lines2011In: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 69, no 3, p. 220-227Article in journal (Refereed)
    Abstract [en]

    The design of the lightning protection system LPS of transmission lines is based on the well knownelectro-geometrical model. The electro-geometrical model assumes that the first point on a powertransmission line that will come within striking distance of the tip of a down-coming stepped leaderchannel is the strike point of the lightning flash. The model neglects almost all of the physics associatedwith the lightning attachment.Nowadays, as it is possible to use modern hardware and software tools and several different numericalmethods, it is feasible to apply the physics of the discharge process to the study of lightning attachment.Such models take into account the movement of the downward and the resulting upward leaders fromdifferent points on the structures under consideration.In this paper, a procedure based on lightning physics was used to analyze the lightning attachmentphenomena in EHV transmission lines of 230 kV and 500 kV and the results were compared with thepredictions of the electro-geometrical method.

  • 11.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Preliminary study on the modelling of negative leader discharges2011In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 44, no 31, p. 315204-Article in journal (Refereed)
    Abstract [en]

    Nowadays, there is considerable interest in understanding the physics underlying positive and negative discharges because of the importance of improving lightning protection systems and of coordinating the insulation for high voltages. Numerical simulations of positive switching impulses made in long spark gaps in a laboratory are achievable because the physics of the process is reasonably well understood and because of the availability of powerful computational methods. However, the existing work on the simulation of negative switching discharges has been held up by a lack of experimental data and the absence of a full understanding of the physics involved. In the scientific community, it is well known that most of the lightning discharges that occur in nature are of negative polarity, and because of their complexity, the only way to understand them is to generate the discharges in laboratories under controlled conditions. The voltage impulse waveshape used in laboratories is a negative switching impulse. With the aim of applying the available information to a self-consistent physical method, an electrostatic approximation of the negative leader discharge process is presented here. The simulation procedure takes into consideration the physics of positive and negative discharges, considering that the negative leader propagates towards a grounded electrode and the positive leader towards a rod electrode. The simulation considers the leader channel to be thermodynamic, and assumes that the conditions required to generate a thermal channel are the same for positive and negative leaders. However, the magnitude of the electrical charge necessary to reproduce their propagation and thermalization is different, and both values are based on experimental data. The positive and negative streamer development is based on the constant electric field characteristics of these discharges, as found during experimental measurements made by different authors. As a computational tool, a finite element method based software is employed. The simulations are compared with experimental data available in the literature.

  • 12.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Reliable model for the calculation of negative leader discharges under switching impulses2010Conference paper (Refereed)
  • 13. Arevalo, Liliana
    et al.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Streamer to leader transition criteria for propagation of long sparks and lightning leaders2014In: 2014 INTERNATIONAL CONFERENCE ON LIGHTNING PROTECTION (ICLP), IEEE conference proceedings, 2014, p. 480-483Conference paper (Refereed)
    Abstract [en]

    Certain models have been dedicated to analyze the breakdown of long spark gaps and the lightning attachment process based on the mechanism of leader propagation. One of the most important processes on the mechanism of leader is the transition between streamers to leader. The streamer to leader transition is characterized by a rapid increase in the electron density and gas temperature, which is a consequence of the onset of thermal-ionization instability. To simplify the complexity of the physical process lightning attachment and long spark gaps models assumed that a minimum charge of 1 mu C is necessary to thermalize a leader channel, independently of the electric field and atmospheric conditions as temperature, pressure and humidity. In this paper an approach that takes into account the continuity equations and the gas temperature balance equation is used to investigate the minimum charge required to start the streamer to leader transition. The obtained results are compared with the minimum charge criteria used for long spark gaps and lightning attachment modeling. Simulation shows that the required charge to thermalize a leader depends on the vibrational energy relaxation. Results also indicate that only a small part of the energy input, transferred by electrons to gas molecules in the stem, contributes immediately to the temperature rise.

  • 14.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    'The mesh method' in lightning protection standards - Revisited2010In: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 68, no 4, p. 311-314Article in journal (Refereed)
    Abstract [en]

    At present the design of the Lightning protection systems (LPS) for structures as stipulated in standards is based on the electro - geometrical method, which was initially used to protect power lines from lightning. A derivative of the electro-geometrical method is the rolling sphere method. This method together, with the protection angle method and mesh method are used almost in all lightning standards as the measure in installing the lightning protection systems of grounded structures. In the mesh method, the dimension of the cell size in different levels of protection is determined using the rolling sphere method. Since the rolling sphere method does not take into account the physics of the lightning attachment process there is a need to evaluate the validity of the stipulated value in standards of the minimum lightning current that can penetrate through the mesh in different levels of protection. In this paper, meshes of different sizes as stipulated in the lightning protection standards were tested for their ability to intercept lightning flashes using a lightning attachment model that takes into account the physics of connecting leaders on. The results are in reasonable agreement with the specifications given in the lightning protection standards.

  • 15.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. Ludvika ULHC, ABB Power Grids Grid Integrat HVDC, Dept Res & Dev, Lyviksvagen 3, S-77180 Lyviksvagen, Sweden..
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Unstable Leader Inception Criteria of Atmospheric Discharges2017In: Atmosphere, ISSN 2073-4433, E-ISSN 2073-4433, Vol. 8, no 9, article id 156Article in journal (Refereed)
    Abstract [en]

    In the literature, there are different criteria to represent the formation of a leader channel in short and long gap discharges. Due to the complexity of the physics of the heating phenomena, and the limitations of the computational resources, a simplified criterion for the minimum amount of electrical charge required to incept an unstable leader has recently been used for modeling long gap discharges and lightning attachments. The criterion is based on the assumption that the total energy of the streamer is used to heat up the gas, among other principles. However, from a physics point of view, energy can also be transferred to other molecular processes, such as rotation, translation, and vibrational excitation. In this paper, the leader inception mechanism was studied based on fundamental particle physics and the energy balance of the gas media. The heating process of the plasma is evaluated with a detailed two-dimensional self-consistent model. The model is able to represent the streamer propagation, dark period, and unsuccessful leaders that may occur prior to the heating of the channel. The main processes that participate in heating the gas are identified within the model, indicating that impact ionization and detachment are the leading sources of energy injection, and that recombination is responsible for loss of electrons and limiting the energy. The model was applied to a well-known experiment for long air gaps under positive switching impulses reported in the literature, and used to validate models for lightning attachments and long gap discharges. Results indicate that the streamer-leader transition depends on the amount of energy transferred to the heating process. The minimum electric charge required for leader inception varies with the gap geometry, the background electric field, the reduction of electric field due to the space charge, the energy expended on the vibrational relation, and the environmental conditions, among others.

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  • 16. Arevalo, Liliana
    et al.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Upward leader inception caused by a sudden change of cloud electric field2014In: 2014 INTERNATIONAL CONFERENCE ON LIGHTNING PROTECTION (ICLP), IEEE conference proceedings, 2014, p. 484-487Conference paper (Refereed)
    Abstract [en]

    Discharge processes such as glow, streamer, and leader inception among others take place before an upward leader can be launched from a grounded structure during thunderstorms. Electrostatic fields below the thundercloud could lead to the formation of glow charge from grounded objects. If the electric field is high enough and ionization keeps expanding into the gap, streamers can be incepted. Depending on the available charge and the thermodynamic properties of the gas, there is a possibility to incept or not a positive upward leader towards the cloud. Usually, the inception of positive upward leaders is directly related with the appearance of a downward coming leader from cloud towards the grounded object. Such a downward leader will intensify the electric field in such a way that the streamer discharges could thermalize and produce an unstable upward leader channel. However, experimental observations have indicated the inception of upward leaders from grounded structures without registering connecting downward leaders towards the structure. The present paper intends to explain the inception of positive upward leaders from the top of a rod, whenever the electric field produced by the cloud suddenly changes e.g. due to intra-cloud discharges or distance cloud to ground flash. A two dimensional model based on the gas-dynamic equations, the main processes responsible for gas heating such as vibrational excitation and transfer of energy into electronic, rotational and translational excitation, coupled with Poisson equation is presented in this paper. Rods of different lengths under thundercloud electric field were studied. Simulation results indicate that positive upward leaders can be incepted from long rods under certain conditions of thundercloud electric field without the need of a coming downward leader. However, for rods of tenths of meters the thundercloud electric field is not enough to incept positive upward leaders and an intensification of the electric field is required in order to incept a positive upward leader from the structure, e.g., a coming downward leader.

  • 17.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Montano, Raul
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Breakdown times and voltages probability calculation using a simplified numerical methodology2008Conference paper (Refereed)
  • 18.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Montano, Raul
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Numerical simulation of long laboratory sparks generated by positive switching impulses2009In: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 67, no 2-3, p. 228-234Article in journal (Refereed)
    Abstract [en]

    A numerical methodology using two different leader channel criteria has been implemented. The methodology is based on Bondiou and Gallimberti's proposition [A. Bondiou, I. Gallimberti, Theoretical modelling of the development of the positive spark in long spark, J. Phys. D: Appl. Phys. 27 (1994) 1252-1266]. The leader channel criteria used are Rizk engineering criterion [Rizk, A model for switching impulse leader inception and breakdown of long air gaps, IEEE Trans. Power Deliv., 4(1) (1989)] and Local thermodynamic - L.T.E. - physical concept [I. Gallimberti, The mechanism of the long spark formation, Colloque C7, J. Phys. (supplement au nro 7, Tome 40) (July 1979) C7-193]. The methodology was tested in three different cases; a deterministic case, a statistical variation and a typical constant level test. Deterministic calculation considered corona inception using stabilization corona electric field criterion of Gallimberti [I. Gallimberti, The mechanism of the long spark formation, Colloque C7, J. Phys. (supplement au nro 7, Tome 40) (July 1979) C7-193] and the leader moving as segments. The statistical simulation has two different statistical delays, one at inception and the other due to the tortuous characteristics of the leader channel. The constant level test consists of 200 positive switching impulses with the same characteristics such as maximum applied voltage, time to crest and time to fall. Time to breakdown and breakdown voltage were found based on the results obtained from the constant level test characteristics. All the numerical results presented are based on experimental conditions reported in [Les Renardières Group, Research on long gap discharges at Les Renardières, Electra N 35 (1973)] from the world class research group namely Les Renardieres Group.

  • 19.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Montano, Raul
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Roman, Franscisco
    Breakdown effect on long gaps under switching impulses statistical variation2008Conference paper (Refereed)
  • 20.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Wu, Dong
    ABB AB, Power systems HVDC, Ludvika.
    Jacobson, Björn
    ABB AB, Power Systems HVDC, Ludvika.
    A new static calculation of the streamer region for long spark gaps2012In: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 70, no 1, p. 15-19Article in journal (Refereed)
    Abstract [en]

    Different electrostatic approximations have been proposed to calculate the streamer region without going in deep details of the behavior of density of particles under the effect of high electric fields; this kind of approximations have been used in numerical calculations of long spark gaps and lightning attachment. The simplifications of the streamer region are achieved by considering it to be a geometrical region with a constant geometrical shape. Different geometrical shapes have been used, such as cones or several parallel filaments. Afterward, to simplify the procedures, the streamer region was approximated by two constants, one denoted K-Q, called the geometrical constant and in other cases K named as geometrical factor. However, when a voltage that varies with time is applied to an arrangement of electrodes (high voltage and grounded electrodes), the background electric field will change with time. Thus, if the background electric field is modified, the streamer zone could cover a larger or smaller area. With the aim of reducing the number of assumptions required in the calculation of long gap discharges, a new electrostatic model to calculate the streamer region is presented. This model considers a variable streamer zone that changes with the electric field variations. The three-dimensional region that fulfills the minimum electric field to sustain a streamer is identified for each time step, and the charge accumulated in that region is then calculated. The only parameter that is being used in the calculation is the minimum electric field necessary for the propagation of streamers.

  • 21.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Wu, Dong
    Jacobson, Björn
    The development of long spark gaps: Simulation including a variable streamer regionArticle in journal (Refereed)
  • 22.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Montano, Raul
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Modelling of Positive Discharges in Laboratory Gaps under Switching impulses2008Conference paper (Refereed)
  • 23.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Wu, Dong
    ABB Power Systems HVDC.
    A consistent approach to estimate the breakdown voltage of high voltage electrodes under positive switching impulses2013In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 114, no 8Article in journal (Refereed)
  • 24.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. ABB Power Systems HVDC.
    Wu, Dong
    ABB Power Systems HVDC.
    Coated large electrodes for corona prevention2013In: International Symposium on High Voltage Engineering ISH, At Seoul Korea, 2013Conference paper (Refereed)
  • 25.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. ABB Power Systems HVDC.
    Wu, Dong
    ABB POwer Systems HVDC.
    INFLUENCE OF RAIN ON THE SWITCHING IMPULSE BREAKDOWN BEHAVIOUR OF POST INSULATOR WITH LARGE ELECTRODE2013In: CIGRE Symposium "Best practice in generation, transmission and distribution in a changing environment", At Auckland, New Zealand / [ed] CIGRE, 2013Conference paper (Refereed)
  • 26.
    Cooray, Vernon
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Arevalo, Liliana
    A Huristic Approach to Obtain the Electric Fields Necessary for the Initiation of Upward Lightning Flashes from Towers in the Presence of Glow Corona2014Conference paper (Refereed)
  • 27.
    Cooray, Vernon
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Arevalo, Liliana
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Modeling the Stepping Process of Negative Lightning Stepped Leaders2017In: Atmosphere, ISSN 2073-4433, E-ISSN 2073-4433, Vol. 8, no 12, article id 245Article in journal (Refereed)
    Abstract [en]

    A physical model based on the mechanism observed in experimental investigations is introduced to describe the formation of negative leader steps. Starting with a small length of a space leader located at the periphery of the negative streamer system of the stepped leader, the model simulates the growth and the subsequent formation of the leader step. Based on the model, the step length, the step forming time, and the propagation speed of stepped leaders as a function of the prospective return stroke peak current are estimated. The results show that the step length and the leader speed increase with increasing prospective return stroke current. The results also show that the speed of the stepped leader increases as it approaches the ground. For prospective return stroke currents in the range of 15 kA–60 kA, the step lengths lie within the range 5 m–100 m, the step forming times lie within the range 10 μs–250 μs, and the leader speed lies within the range 105 m/s −1.5 × 106 m/s. The results obtained are in reasonable agreement with the experimental observations.

  • 28.
    Cooray, Vernon
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Fernando, Mahendra
    Arevalo, Liliana
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Becerra, Marley
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Interaction of multiple connecting leaders issued from a grounded structure simulated using a self consistent leader inception and propagation model SLIM2010In: 30TH International Conference on Lightning Protection, ICLP, Cagliary, Italy, 2010Conference paper (Refereed)
  • 29.
    Diaz, Oscar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Arevalo, Liliana
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Leader channel models for long air positive electrical discharges2015In: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 76, p. 208-215Article in journal (Refereed)
    Abstract [en]

    The models proposed for the positive long air gap electrical discharge can be considered to be either engineering or physical in their approach. In this work, we make a general review of the available models and use two of them for a comparison with experimental data. Common underlying assumptions were found in most of the models analyzed. The comparison with the experimental data revealed that the results obtained from the models were a good representation of the physical situation when the leader potential distribution and the leader-corona region evolution were described with certain physical assumptions.

  • 30.
    Diaz, Oscar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Arevalo, Liliana
    ABB Power Syst HVDC, SE-77180 Ludvika, Sweden.
    Cooray, Vernon
    Parameter variation in leader channel models used in long air gap discharge simulation2016In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 139, p. 32-36Article in journal (Refereed)
    Abstract [en]

    Theoretical models have been developed to predict the 50% breakdown voltage of long air gaps arrangements, based on the physics of the discharge. These models are capable of estimating electric fields, leader and streamer region propagation, among others. An important parameter within this calculation is the leader model and its electric potential distribution along the discharge channel. In the present work, we compared engineering and physical leader models against experimental data recorded for a rod-to-plane electrode arrangement tested with switching-like voltage impulses. The analysis showed that the leader channel evolution depends strongly on the potential gradient assumed to sustain streamers.

  • 31.
    Diaz, Oscar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Arevalo, Liliana
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. HVDC ABB AB.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Antonio, Mejia
    National University of Colombia.
    Electrical breakdown in soil under uniform background electric fields2010Conference paper (Refereed)
    Abstract [en]

    The present study deals with the electrical breakdown in soil while being subjected to lightning-like voltage impulses for uniform background electric field and short interelectrodic distances. Most of the scientific work in soils and its component’s electrical properties focuses on power grounding systems and how they behave while managing low frequency and high impulse currents.

    The used sand sample was tested in a sphere-sphere electrode configuration with a variable gap distance between 1 and 6mm. The sand sample and electrodes were contained in a cylindrical insulating test cell. The sand sample humidity content (HC) was carefully controlled at values of equilibrium moisture content (EMC), 3%, 7% and 11%. The voltage and current signatures were measured with shielded signal wires and a grounded metallic cabin for the digital oscilloscope.

      The equivalent electrical impedance of the sand sample, calculated as the ratio between voltage and current, showed a dynamic behavior depending on the sample humidity and the current following between the electrodes.

  • 32.
    Diaz, Oscar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Arevalo, Liliana
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. HVDC ABB AB.
    Methodologies for the charge estimation in the leader corona region used in modeling long air gaps underpositive voltage impulses2016Conference paper (Refereed)
    Abstract [en]

    Different methodologies have been proposed to represent the physical phenomena taking place in a laboratory electrical breakdown event. The implementation of these methodologies in numerical routines is based in several physical assumptions and a proper calculation of the electrostatic potential distribution. The whole electrical breakdown in air tested with switching-like voltage impulses can be subdivided into three main stages: first, the streamer inception (first corona), then the streamer to leader transition (second corona, leader inception) and the leader propagation. An important element in the last stage is the representation of the leader corona region (streamer region) in front of the leader tip channel as it propagates towards ground. In this paper, with the aid of a finite element method solver to determine the electric potential distribution, two new methodologies to quantify the amount of charge produced in the leader corona region were presented and compared with other ones available in the literature.

  • 33.
    Diaz, Oscar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Arevalo, Liliana
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. ABB AB, HVDC PGGI, Div Res & Dev, S-77180 Ludvika, Sweden.
    Numerical Modeling of Electrical Discharges in Long Air Gaps Tested With Positive Switching Impulses2018In: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 46, no 3, p. 611-621Article in journal (Refereed)
    Abstract [en]

    The numerical modeling of electrical discharges occurring in atmospheric air has been in continuous development during the past decades in different fields, such as high-voltage techniques and lightning protection. Different methodologies have been proposed to represent the physical phenomena taking place at a single full discharge event, departing both from experimental and theoretical approaches. The implementation of these methodologies in numerical routines combined with the use of numerical methods to determine the electric potential distribution permits the creation of models whose predictions closely agree with the real case situations, where electrode arrangements might have nonsymmetric geometries. In this paper, we present an improved version of a simulation methodology for representing electrical discharges in long air gaps. This simulation methodology includes new elements like: 1) the 3-D leader channel tortuosity based on laboratory experimental measurements and 2) two new methods for the estimation of the electric charge contained in the so-called leader-corona region based on the electrostatic potential of fictitious potential rings representing the active region in front of the leader tip. Results from the simulation were compared with experimental records and a reasonably good agreement is found between them.

  • 34.
    Diaz, Oscar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Arevalo, Liliana
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. HVDC ABB AB.
    Sensitivity Analysis of Leader Channel Models Used in Long Air Gap Positive Discharge Modelling2014In: 2014 INTERNATIONAL CONFERENCE ON LIGHTNING PROTECTION (ICLP), IEEE conference proceedings, 2014, p. 564-567Conference paper (Refereed)
    Abstract [en]

    Leader models used in electrical discharge simulation have been proposed in theoretical works by different authors. Their application can be found in the study of lightning upward connecting leaders or long air gap laboratory testing, and can be considered engineering or physical according to their detail level. Based on simplifications and assumptions, these models are capable of predicting the 50% breakdown voltage for certain electrode arrangements, time evolution of physical phenomena like particle densities, temperatures, electric fields, leader and streamer progress, among others. An important parameter in a leader model is the potential distribution along the channel as it propagates. In present work, we compare an engineering and a physical leader model against experimental data recorded while testing a rod-to-plane 10 m gap with switching-like voltage impulse. A sensitivity analysis was done with some basic input parameters of two leader models in order to compare the outcome for different cases. The results showed a strong dependence of the leader channel evolution with the assumed constant average potential gradient used in most of the leader models.

1 - 34 of 34
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