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Becerra Garcia, MarleyORCID iD iconorcid.org/0000-0002-6375-6142
Alternative names
Publications (10 of 78) Show all publications
Cuaran, J., Becerra Garcia, M. & Roman, F. (2019). Lightning Attachment to UHV Power Transmission Lines: Effect of the Phase Voltage. IEEE Transactions on Power Delivery, 34(2), 729-738
Open this publication in new window or tab >>Lightning Attachment to UHV Power Transmission Lines: Effect of the Phase Voltage
2019 (English)In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 34, no 2, p. 729-738Article in journal (Refereed) Published
Abstract [en]

The self-consistent leader inception and propagation model is used to analyze the influence of the phase voltage on the attachment of lightning to ultra-high voltage power transmission lines (UHV-TLs). An UHV-ac line with shielding failures reported in the literature is used as a case study. It is shown that the length of upward leaders initiated fromconductors and their striking distances are longer under positive voltages than when energized with the opposite polarity. Therefore, the fraction of shielding failures of each conductor changes significantly with the phase angle in ac lines. However, it is found that the overall effect of voltage on lightning attachment can also be limited by the electrostatic screening produced by shield wires and their leaders. This proximity effect mainly reduces the velocity of upward leaders launched from energized conductors. Therefore, the effect of voltage on the lightning attachment process cannot be generalized since it is strongly coupled to the proximity of shield wires and their associated leaders. Thus, the lightning shielding performance should consider case-to-case variations in the upward leader velocity in different UHV-TLs designs, given not only by the line voltage but also coupled to the proximity of other wires and their launched leaders.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2019
Keywords
Lightning, power transmission, UHV transmission lines, Physics
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-249865 (URN)10.1109/TPWRD.2018.2885161 (DOI)000462414900034 ()2-s2.0-85058117930 (Scopus ID)
Note

QC 20190426

Available from: 2019-04-26 Created: 2019-04-26 Last updated: 2019-04-26Bibliographically approved
Aljure, M., Becerra Garcia, M. & Karlsson, M. E. (2019). On the injection and generation of charge carriers in mineral oil under high electric fields. JOURNAL OF PHYSICS COMMUNICATIONS, 3(3), Article ID UNSP 035019.
Open this publication in new window or tab >>On the injection and generation of charge carriers in mineral oil under high electric fields
2019 (English)In: JOURNAL OF PHYSICS COMMUNICATIONS, ISSN 2399-6528, Vol. 3, no 3, article id UNSP 035019Article in journal (Refereed) Published
Abstract [en]

Charge injection and generation mechanisms under intense electric fields (up to 10(9)Vm(-1)) in mineral oil are assessed experimentally and numerically. For this, current-voltage characteristics under positive and negative polarities are measured in a needle-plane configuration using sharp needles (with tip radius R-tip <= 1.1 mu m). In addition, a state of the art electro-hydrodynamic (EHD) model is implemented to calculate the contribution of the different mechanisms on the high-field conduction currents in the liquid. In order to evaluate exclusively the contribution of field emission, experiments are also performed in vacuum. It is found that neither field emission nor field ionisation can explain the conduction currents measured in mineral oil. It is proposed that field molecular ionisation, as described by Zener tunnelling model for solids, and electron impact ionisation are the processes dominating the generation of excess electron-ion pairs in mineral oil under positive and negative polarity, respectively. It is also shown that Zener molecular ionisation alone grossly overestimates the measured currents when parameters previously suggested in the literature for mineral oil are used. Preliminary model parameters for these mechanisms that best fit the conduction currents measured in mineral oil are presented and discussed.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2019
Keywords
electrical conduction, electrohydrodynamics, mineral oil, excess carriers, RENZO SE, 1974, PHYSICAL REVIEW A, V9, P2582 ng N. V., 2012, IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION, V19, P1593, NAT A, 1988, IEEE TRANSACTIONS ON ELECTRICAL INSULATION, V23, P545 ang J. George, 2012, IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION, V19, P162 ten P, 1996, IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION, V3, P1 rrow R, 1999, JOURNAL OF PHYSICS D-APPLIED PHYSICS, V32, PL20 nas, 2006, Nytro 10X Safety Data Sheet, P1, VINS JC, 1981, JOURNAL OF APPLIED PHYSICS, V52, P4531 rbes Richard G., 2007, PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, V463, P2907 nat A., 2006, IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION15th IEEE International Conference on Dielectric Liquids, JUN 26-JUL 01, 2005, Coimbra, PORTUGAL, V13, P518 tcher M, 2006, IEEE TRANSACTIONS ON PLASMA SCIENCE, V34, P467
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-249818 (URN)10.1088/2399-6528/ab0d59 (DOI)000463117800019 ()
Note

QC 20190423

Available from: 2019-04-23 Created: 2019-04-23 Last updated: 2019-08-01Bibliographically approved
Pettersson, J., Becerra Garcia, M., Franke, S. & Gortschakow, S. (2019). Spectroscopic and Photographic Evaluation of the Near-Surface Layer Produced by Arc-Induced Polymer Ablation. IEEE Transactions on Plasma Science, 47(4), 1851-1858
Open this publication in new window or tab >>Spectroscopic and Photographic Evaluation of the Near-Surface Layer Produced by Arc-Induced Polymer Ablation
2019 (English)In: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 47, no 4, p. 1851-1858Article in journal (Refereed) Published
Abstract [en]

High-intensity plasmas can release material from the surface of polymers by a process known as arc-induced ablation. As consequence, the formation of a near-surface layer of polymeric vapor is generally assumed. In order to investigate the near-surface layer formed by the ablation of polyoxymethylene, high-speed photography and space-resolved optical emission spectroscopy are used. Transient arc plasmas generated under a 1.9-kA, 50-Hz current semicycle are used as ablation source in air. It is found that the near-surface ablation layer strongly scatters radiation emitted by the arc core. This effect is caused by light scattering of micrometer-size fragments released by the ablating polymer. This finding shows that the near-surface layer is not only composed of vapor but also contains a significant density of large-sized polymer fragments. These fragments are formed a few milliseconds after the ignition of the arc plasma, and their density rapidly decreases with the distance to the surface.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2019
Keywords
Arc plasma, optical emission spectroscopy, polymer ablation, scattering, vapor layer
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-249795 (URN)10.1109/TPS.2019.2898632 (DOI)000463470900021 ()2-s2.0-850639350772-s2.0-85063935077 (Scopus ID)
Note

QC 20190424

Available from: 2019-04-24 Created: 2019-04-24 Last updated: 2019-04-24Bibliographically approved
Parekh, M., Magnusson, J., Becerra Garcia, M. & Engdahl, G. (2018). Effect of contact velocity on the behaviour of decaying arcs in air. In: PROCEEDINGS OF 2018 29TH INTERNATIONAL CONFERENCE ON ELECTRICAL CONTACTS AND 64TH IEEE HOLM CONFERENCE ON ELECTRICAL CONTACTS: . Paper presented at Joint Meeting of the 29th International Conference on Electrical Contacts (ICEC) / 64th IEEE Holm Conference on Electrical Contacts, OCT 14-18, 2018, Albuquerque, NM (pp. 77-80). IEEE
Open this publication in new window or tab >>Effect of contact velocity on the behaviour of decaying arcs in air
2018 (English)In: PROCEEDINGS OF 2018 29TH INTERNATIONAL CONFERENCE ON ELECTRICAL CONTACTS AND 64TH IEEE HOLM CONFERENCE ON ELECTRICAL CONTACTS, IEEE , 2018, p. 77-80Conference paper, Published paper (Refereed)
Abstract [en]

Hybrid direct current circuit breaker (HDCCB) consists of an ultra-fast electromechanical switch combined with power semiconductors to interrupt fault currents. When the ultra-fast electromechanical switch opens, arc plasma is generated between its contacts that commutate the fault current to the auxiliary circuit consisting of power semiconductors. Understanding of the arc behaviour due to the ultra-fast contact opening is necessary as the current commutation is driven by the arc voltage. This paper presents experimental results of a dynamic voltage-current (V-I) characteristics of a decaying arc plasma in air having contact opening velocities from 5 to 15 m/s. A pair of hemispherically capped copper contacts was used for the experiments. The contacts were covered by a glass tube, open from one end which makes the arc partially wall constricted. The contacts were opened with a dedicated Thomson coil based electromagnetic actuator. A computer controlled test system was used that allowed controlling the shape of the current pulse and the time instant of the contact opening on the current waveform. The conductance of the arc was calculated for different contact opening velocities. It was observed that the conductance decreased with an increase of the contact opening velocity. High speed imaging was performed to observe the physical behaviour of arcs having different contact opening speeds.

Place, publisher, year, edition, pages
IEEE, 2018
Series
Electrical Contacts-IEEE Holm Conference on Electrical Contacts, ISSN 1062-6808
Keywords
contact velocity, ultra-fast electromechanical switch, hybrid direct current circuit breaker, electrical arc
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-246307 (URN)10.1109/HOLM.2018.8611733 (DOI)000459880000013 ()2-s2.0-85061821689 (Scopus ID)978-1-5386-6315-8 (ISBN)
Conference
Joint Meeting of the 29th International Conference on Electrical Contacts (ICEC) / 64th IEEE Holm Conference on Electrical Contacts, OCT 14-18, 2018, Albuquerque, NM
Note

QC 20190320

Available from: 2019-03-20 Created: 2019-03-20 Last updated: 2019-03-20Bibliographically approved
Parekh, M., Magnusson, J., Becerra Garcia, M. & Engdahl, G. (2018). Effect of contact velocity on the behaviour of decaying arcs in air. In: IEEE (Ed.), 2018 IEEE Holm Conference on Electrical Contacts: . Paper presented at 2018 IEEE Holm Conference on Electrical Contacts, 14-18 Oct. 2018, Albuquerque, NM, USA (pp. 77-80). Albuquerque, NM, USA: Institute of Electrical and Electronics Engineers (IEEE), Article ID 8611733.
Open this publication in new window or tab >>Effect of contact velocity on the behaviour of decaying arcs in air
2018 (English)In: 2018 IEEE Holm Conference on Electrical Contacts / [ed] IEEE, Albuquerque, NM, USA: Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 77-80, article id 8611733Conference paper, Published paper (Refereed)
Abstract [en]

Hybrid direct current circuit breaker (HDCCB) consists of an ultra-fast electromechanical switch combined with power semiconductors to interrupt fault currents. When the ultra-fast electromechanical switch opens, arc plasma is generated between its contacts that commutate the fault current to the auxiliary circuit consisting of power semiconductors. Understanding of the arc behaviour due to the ultra-fast contact opening is necessary as the current commutation is driven by the arc voltage. This paper presents experimental results of a dynamic voltage-current (V-I) characteristics of a decaying arc plasma in air having contact opening velocities from 5 to 15 m/s. A pair of hemispherically capped copper contacts was used for the experiments. The contacts were covered by a glass tube, open from one end which makes the arc partially wall constricted. The contacts were opened with a dedicated Thomson coil based electromagnetic actuator. A computer controlled test system was used that allowed controlling the shape of the current pulse and the time instant of the contact opening on the current waveform. The conductance of the arc was calculated for different contact opening velocities. It was observed that the conductance decreased with an increase of the contact opening velocity. High speed imaging was performed to observe the physical behaviour of arcs having different contact opening speeds.

Place, publisher, year, edition, pages
Albuquerque, NM, USA: Institute of Electrical and Electronics Engineers (IEEE), 2018
Series
Electrical Contacts, Proceedings of the Annual Holm Conference on Electrical Contacts, ISSN 03614395
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-246334 (URN)10.1109/HOLM.2018.8611733 (DOI)2-s2.0-85061821689 (Scopus ID)978-1-5386-6315-8 (ISBN)
Conference
2018 IEEE Holm Conference on Electrical Contacts, 14-18 Oct. 2018, Albuquerque, NM, USA
Note

QC 20190319

Available from: 2019-03-18 Created: 2019-03-18 Last updated: 2019-03-19Bibliographically approved
Parekh, M., Magnusson, J., Becerra Garcia, M. & Engdahl, G. (2018). Effect of contact velocity on the behaviour of decaying arcs in air. In: Effect of contact velocity on the behaviour of decaying arcs in air: . Paper presented at 2018 IEEE Holm Conference on Electrical Contacts. Albuquerque, NM, USA, USA: IEEE
Open this publication in new window or tab >>Effect of contact velocity on the behaviour of decaying arcs in air
2018 (English)In: Effect of contact velocity on the behaviour of decaying arcs in air, Albuquerque, NM, USA, USA: IEEE, 2018Conference paper, Published paper (Refereed)
Abstract [en]

Hybrid direct current circuit breaker (HDCCB) consists of an ultra-fast electromechanical switch combined with power semiconductors to interrupt fault currents. When the ultra-fast electromechanical switch opens, arc plasma is generated between its contacts that commutate the fault current to the auxiliary circuit consisting of power semiconductors. Understanding of the arc behaviour due to the ultra-fast contact opening is necessary as the current commutation is driven by the arc voltage. This paper presents experimental results of a dynamic voltage-current (V-I) characteristics of a decaying arc plasma in air having contact opening velocities from 5 to 15 m/s. A pair of hemispherically capped copper contacts was used for the experiments. The contacts were covered by a glass tube, open from one end which makes the arc partially wall constricted. The contacts were opened with a dedicated Thomson coil based electromagnetic actuator. A computer controlled test system was used that allowed controlling the shape of the current pulse and the time instant of the contact opening on the current waveform. The conductance of the arc was calculated for different contact opening velocities. It was observed that the conductance decreased with an increase of the contact opening velocity. High speed imaging was performed to observe the physical behaviour of arcs having different contact opening speeds.

Place, publisher, year, edition, pages
Albuquerque, NM, USA, USA: IEEE, 2018
Series
2018 IEEE Holm Conference on Electrical Contacts, ISSN 1062-6808, E-ISSN 2158-9992
Keywords
contact velocity, ultra-fast electromechanical switch, hybrid direct current circuit breaker, electrical arc
National Category
Engineering and Technology
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-241448 (URN)10.1109/HOLM.2018.8611733 (DOI)978-1-5386-6315-8 (ISBN)
Conference
2018 IEEE Holm Conference on Electrical Contacts
Note

QC 20190125

Available from: 2019-01-22 Created: 2019-01-22 Last updated: 2019-05-10Bibliographically approved
Aljure, M., Becerra Garcia, M. & Karlsson, M. (2018). Erratum to: Aljure, M.; Becerra, M.; Karlsson, E.M. Streamer inception from ultra-sharp needles in mineral oil based nanofluids. Energies, 11(11), Article ID 2900.
Open this publication in new window or tab >>Erratum to: Aljure, M.; Becerra, M.; Karlsson, E.M. Streamer inception from ultra-sharp needles in mineral oil based nanofluids
2018 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, no 11, article id 2900Article in journal (Refereed) Published
Abstract [en]

The authors wish to make the following corrections to their paper [1]: i. On pages 13 and 14, the numbering of references from 17 to 30 is incorrect. References 17 to 30 should be renumbered from the original order below: 17. Liu, Z.; Liu, Q.; Wang, Z.D.; Jarman, P.; Krause, C.; Smith, P.W.R.; Gyore, A. Partial discharge behaviour of transformer liquids and the influence of moisture content. In Proceedings of the 2014 IEEE 18th International Conference on Dielectric Liquids (ICDL), Bled, Slovenia, 29 June–3 July 2014. 18. Yamashita, H.; Yamazawa, K.; Wang, Y.S. The effect of tip curvature on the prebreakdown streamer structure in cyclohexane. IEEE Trans. Dielectr. Electr. Insul. 1998, 5, 396–401. 19. Dumitrescu, L.; Lesaint, O.; Bonifaci, N.; Denat, A.; Notingher, P. Study of streamer inception in cyclohexane with a sensitive charge measurement technique under impulse voltage. J. Electrostat. 2001, 53, 135–146. 20. Pourrahimi, A.M.; Hoang, T.A.; Liu, D.; Pallon, L.K.H.; Gubanski, S.; Olsson, R.T.; Gedde, U.W.; Hedenqvist, M.S. Highly efficient interfaces in nanocomposites based on polyethylene and ZnO nano/hierarchical particles: A novel approach toward ultralow electrical conductivity insulations. Adv. Mater. 2016, 28, 8651–8657. 21. Li, J.; Du, B.; Wang, F.; Yao, W.; Yao, S. The effect of nanoparticle surfactant polarization on trapping depth of vegetable insulating oil-based nanofluids. Phys. Lett. A 2016, 380, 604–608. 22. Aljure, M.; Becerra, M.; Pallon, L.K.H. Electrical conduction currents of a mineral oil-based nanofluid in needle-plane configuration. In Proceedings of the 2016 IEEE Conference on Electrical Insulation and Dielectric Phenomena (CEIDP), Toronto, ON, Canada, 16–19 October 2016; pp. 687–690. 23. Primo, V.A.; Garcia, B.; Albarracin, R. Improvement of transformer liquid insulation using nanodielectric fluids: A review. IEEE Electr. Insul. Mag. 2018, 34, 13–26. 24. Jin, H.; Andritsch, T.; Morshuis, P.H.F.; Smit, J.J. AC breakdown voltage and viscosity of mineral oil based SiO2 nanofluids. In Proceedings of the 2012 Annual Report Conference on Electrical Insulation and Dielectric Phenomena, Montreal, QC, Canada, 14–17 October 2012; pp. 902–905. 25. Jin, H.; Morshuis, P.; Mor, A.R.; Smit, J.J.; Andritsch, T. Partial discharge behavior of mineral oil based nanofluids. IEEE Trans. Dielectr. Electr. Insul. 2015, 22, 2747–2753. 26. Du, Y.; Lv, Y.; Li, C.; Chen, M.; Zhong, Y.; Zhou, J.; Li, X.; Zhou, Y. Effect of semiconductive nanoparticles on insulating performances of transformer oil. IEEE Trans. Dielectr. Electr. Insul. 2012, 19, 770–776. 27. Dung, N.V.; Høidalen, H.K.; Linhjell, D.; Lundgaard, L.E.; Unge, M. Effects of reduced pressure and additives on streamers in white oil in long point-plane gap. J. Phys. D Appl. Phys. 2013, 46, 255501. 28. McCool, J.I. Using the Weibull Distribution; John Wiley &amp; Sons, Inc.: Hoboken, NJ, USA, 2012. 29. Lesaint, O.L.; Top, T.V. Streamer initiation in mineral oil. part I: Electrode surface effect under impulse voltage. IEEE Trans. Dielectr. Electr. Insul. 2002, 9, 84–91. 30. Becerra, M.; Frid, H.; Vázquez, P.A. Self-consistent modeling of laminar electrohydrodynamic plumes from ultra-sharp needles in cyclohexane. Phys. Fluids 2017, 29, 123605. to the following, corrected numbering: 17. Dumitrescu, L.; Lesaint, O.; Bonifaci, N.; Denat, A.; Notingher, P. Study of streamer inception in cyclohexane with a sensitive charge measurement technique under impulse voltage. J. Electrostat. 2001, 53, 135–146. 18. Liu, Z.; Liu, Q.; Wang, Z.D.; Jarman, P.; Krause, C.; Smith, P.W.R.; Gyore, A. Partial discharge behaviour of transformer liquids and the influence of moisture content. In Proceedings of the 2014 IEEE 18th International Conference on Dielectric Liquids (ICDL), Bled, Slovenia, 29 June–3 July 2014. 19. Yamashita, H.; Yamazawa, K.; Wang, Y.S. The effect of tip curvature on the prebreakdown streamer structure in cyclohexane. IEEE Trans. Dielectr. Electr. Insul. 1998, 5, 396–401. 20. Becerra, M.; Frid, H.; Vázquez, P.A. Self-consistent modeling of laminar electrohydrodynamic plumes from ultra-sharp needles in cyclohexane. Phys. Fluids 2017, 29, 123605. 21. Pourrahimi, A.M.; Hoang, T.A.; Liu, D.; Pallon, L.K.H.; Gubanski, S.; Olsson, R.T.; Gedde, U.W.; Hedenqvist, M.S. Highly efficient interfaces in nanocomposites based on polyethylene and ZnO nano/hierarchical particles: A novel approach toward ultralow electrical conductivity insulations. Adv. Mater. 2016, 28, 8651–8657. 22. Li, J.; Du, B.; Wang, F.; Yao, W.; Yao, S. The effect of nanoparticle surfactant polarization on trapping depth of vegetable insulating oil-based nanofluids. Phys. Lett. A 2016, 380, 604–608. 23. Aljure, M.; Becerra, M.; Pallon, L.K.H. Electrical conduction currents of a mineral oil-based nanofluid in needle-plane configuration. In Proceedings of the 2016 IEEE Conference on Electrical Insulation and Dielectric Phenomena (CEIDP), Toronto, ON, Canada, 16–19 October 2016; pp. 687–690. 24. Primo, V.A.; Garcia, B.; Albarracin, R. Improvement of transformer liquid insulation using nanodielectric fluids: A review. IEEE Electr. Insul. Mag. 2018, 34, 13–26. 25. Jin, H.; Andritsch, T.; Morshuis, P.H.F.; Smit, J.J. AC breakdown voltage and viscosity of mineral oil based SiO2 nanofluids. In Proceedings of the 2012 Annual Report Conference on Electrical Insulation and Dielectric Phenomena, Montreal, QC, Canada, 14–17 October 2012; pp. 902–905. 26. Jin, H.; Morshuis, P.; Mor, A.R.; Smit, J.J.; Andritsch, T. Partial discharge behavior of mineral oil based nanofluids. IEEE Trans. Dielectr. Electr. Insul. 2015, 22, 2747–2753. 27. Du, Y.; Lv, Y.; Li, C.; Chen, M.; Zhong, Y.; Zhou, J.; Li, X.; Zhou, Y. Effect of semiconductive nanoparticles on insulating performances of transformer oil. IEEE Trans. Dielectr. Electr. Insul. 2012, 19, 770–776. 28. Dung, N.V.; Høidalen, H.K.; Linhjell, D.; Lundgaard, L.E.; Unge, M. Effects of reduced pressure and additives on streamers in white oil in long point-plane gap. J. Phys. D Appl. Phys. 2013, 46, 255501. 29. McCool, J.I. Using the Weibull Distribution; John Wiley &amp; Sons, Inc.: Hoboken, NJ, USA, 2012. 30. Lesaint, O.L.; Top, T.V. Streamer initiation in mineral oil. part I: Electrode surface effect under impulse voltage. IEEE Trans. Dielectr. Electr. Insul. 2002, 9, 84–91. ii. On the last paragraph of page 9, the last sentence should be changed from: However, the results in [11] also show the consistent increase in the initiation voltage of prebreakdown phenomena in both polarities, as reported in Figure 11. to the following, corrected version: However, the results in [26] also show the consistent increase in the initiation voltage of prebreakdown phenomena in both polarities, as reported in Figure 11. iii. On the last paragraph of page 10, the third sentence should be changed from: Even though the existing hypotheses of the dielectric effect of NPs [8–10] were proposed for blunter electrodes (where charge generation before streamer initiation is less important [30]), they should still apply under the experimental conditions here reported. to the following, corrected version: Even though the existing hypotheses of the dielectric effect of NPs [5,6,16] were proposed for blunter electrodes (where charge generation before streamer initiation is less important [30]), they should still apply under the experimental conditions here reported. The authors would like to apologize for any inconvenience caused to the readers by these changes. The changes do not affect the scientific results. The manuscript will be updated and the original will remain online on the article webpage, with a reference to this Correction.

Place, publisher, year, edition, pages
MDPI AG, 2018
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:kth:diva-247088 (URN)10.3390/en11112900 (DOI)2-s2.0-85057570828 (Scopus ID)
Note

QC 20190404

Available from: 2019-04-04 Created: 2019-04-04 Last updated: 2019-04-04Bibliographically approved
Becerra Garcia, M., Long, M., Schulz, W. & Thottappillil, R. (2018). On the estimation of the lightning incidence to offshore wind farms. Electric power systems research, 157, 211-226
Open this publication in new window or tab >>On the estimation of the lightning incidence to offshore wind farms
2018 (English)In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 157, p. 211-226Article in journal (Refereed) Published
Abstract [en]

Field observations have shown that the frequency of dangerous lightning events to wind turbines, calculated according to the IEC standard 61400-24:2010, is grossly underestimated. This paper intends to critically revisit the evaluation of the incidence of downward lightning as well as self-initiated and other-triggered upward flashes to offshore wind power plants. Three different farms are used as case studies. The conditions for interception of stepped leaders in downward lightning and the initiation of upward lightning is evaluated with the Self-consistent Leader Inception and Propagation Model (SLIM). The analysis shows that only a small fraction of damages observed in the analysed farms can be attributed to downward lightning. It is also estimated that only a small fraction (less than 19%) of all active thunderstorms in the area of the analysed farms can generate sufficiently high thundercloud fields to self-initiate upward lightning. Furthermore, it is shown that upward flashes can be triggered even under low thundercloud fields once a sufficiently high electric field change is generated by a nearby lightning event. Despite of the uncertainties in the incidence evaluation, it is shown that upward flashes triggered by nearby positive cloud-to-ground flashes produce most of the dangerous lightning events to the case studies.

Place, publisher, year, edition, pages
Elsevier Ltd, 2018
Keywords
Lightning, Lightning damage, Risk assessment, Upward lightning, Wind power farms, Clouds, Damage detection, Electric fields, Standards, Wind power, Wind turbines, Downward lightnings, Field observations, High electric fields, Offshore wind power plants, Positive cloud-to-ground flashes, Propagation modeling, Offshore wind farms
National Category
Environmental Engineering
Identifiers
urn:nbn:se:kth:diva-223115 (URN)10.1016/j.epsr.2017.12.008 (DOI)000425203500021 ()2-s2.0-85039859714 (Scopus ID)
Note

Export Date: 13 February 2018; Article; CODEN: EPSRD; Correspondence Address: Becerra, M.; KTH Royal Institute of Technology, Department of Electromagnetic EngineeringSweden; email: marley@kth.se. QC 20180327

Available from: 2018-03-27 Created: 2018-03-27 Last updated: 2018-03-27Bibliographically approved
Becerra Garcia, M. & Pettersson, J. (2018). Optical radiative properties of ablating polymers exposed to high-power arc plasmas. Journal of Physics D: Applied Physics, 51(12), Article ID 125202.
Open this publication in new window or tab >>Optical radiative properties of ablating polymers exposed to high-power arc plasmas
2018 (English)In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 51, no 12, article id 125202Article in journal (Refereed) Published
Abstract [en]

The radiative properties of polymers exposed to high-intensity radiation are of importance for the numerical simulation of arc-induced ablation. The paper investigates the optical properties of polymethylmethacrylate PMMA and polyamide PA6 films exposed to high-power arc plasmas, which can cause ablation of the material. A four-flux radiative approximation is first used to estimate absorption and scattering coefficients of the tested materials in the ultraviolet (UV) and in the visible (VIS) ranges from spectrophotometric measurements. The temperature-induced variation of the collimated transmissivity of the polymers is also measured from room temperature to the glass temperature of PMMA and the melting temperature of PA6. Furthermore, band-averaged absorption and scattering coefficients of non-ablating and ablating polymers are estimated from the UV to the short-wavelength infrared (SWIR), covering the range of interest for the simulation of arc-induced ablation. These estimates are obtained from collimated transmissivities measured with an additional in situ photometric system that uses a high-power, transient arc plasma to both illuminate the samples and to induce ablation. It is shown that the increase in the bulk temperature of PA6 leads to a strong reversible increase in collimated transmissivity, significantly reducing the absorption and scattering coefficients of the material. A weaker but opposite effect of temperature on the optical properties is found in PMMA. As a consequence, it is suggested that the absorption coefficient of polymers used for arc-induced ablation estimates should not be taken directly from direct collimated transmissivity measurements at room temperature. The band-averaged radiation measurements also show that the layer of products released by ablation of PMMA produces scattering radiation losses mainly in the VIS-SWIR ranges, which are only a small fraction of the total incident arc radiation. In a similar manner, the ablation layer of PA6 leads to weak absorption radiation losses, although mainly in the UV range.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2018
Keywords
radiative properties, polymers, arc plasmas, polymer ablation, spectrophotometry
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-224676 (URN)10.1088/1361-6463/aaaeda (DOI)000426377800001 ()2-s2.0-85043500706 (Scopus ID)
Funder
StandUp
Note

QC 20180323

Available from: 2018-03-23 Created: 2018-03-23 Last updated: 2018-03-23Bibliographically approved
Aljure, M., Becerra Garcia, M. & Karlsson, M. E. (2018). Streamer Inception from Ultra-Sharp Needles in Mineral Oil Based Nanofluids. Energies, 11(8), Article ID 2064.
Open this publication in new window or tab >>Streamer Inception from Ultra-Sharp Needles in Mineral Oil Based Nanofluids
2018 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, no 8, article id 2064Article in journal (Refereed) Published
Abstract [en]

Positive and negative streamer inception voltages from ultra-sharp needle tips (with tip radii below 0.5 m) are measured in TiO2, SiO2, Al2O3, ZnO and C-60 nanofluids. The experiments are performed at several concentrations of nanoparticles dispersed in mineral oil. It is found that nanoparticles influence positive and negative streamers in different ways. TiO2, SiO2 and Al2O3 nanoparticles increase the positive streamer inception voltage only, whilst ZnO and C-60 nanoparticles augment the streamer inception voltages in both polarities. Using these results, the main hypotheses explaining the improvement in the dielectric strength of the host oil due to the presence of nanoparticles are analyzed. It is found that the water adsorption hypothesis of nanoparticles is consistent with the increments in the reported positive streamer inception voltages. It is also shown that the hypothesis of nanoparticles reducing the electron velocity by hopping transport mechanisms fails to explain the results obtained for negative streamers. Finally, the hypothesis of nanoparticles attaching electrons according to their charging characteristics is found to be consistent with the results hereby presented on negative streamers.

Place, publisher, year, edition, pages
MDPI, 2018
Keywords
streamer inception, electric discharges, nanofluids, mineral oil
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:kth:diva-238926 (URN)10.3390/en11082064 (DOI)000446604100143 ()2-s2.0-85052822998 (Scopus ID)
Note

QC 20181114

Available from: 2018-11-14 Created: 2018-11-14 Last updated: 2019-08-01Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6375-6142

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