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  • 51.
    Leijon, Mats
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Danielsson, Oskar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Eriksson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Thorburn, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Bernhoff, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Isberg, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Sundberg, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Ivanova, Irina
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Sjöstedt, Elisabet
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Ågren, Olov
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Karlsson, Karl Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Wolfbrandt, Arne
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    An electrical approach to wave energy conversion2006In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, no 31, p. 1309-1319Article in journal (Refereed)
    Abstract [en]

    Motions in nature, for example ocean waves, can play a significant role in tomorrow's electricity production, but the constructions require adaptations to its media. Engineers planning hydropower plants have always taken natural conditions, such as fall height, speed of flow, and geometry, as basic design parameters and constraints in the design. The present paper describes a novel approach for electric power conversion of the vast ocean wave energy. The suggested linear electric energy converter is adapted to the natural wave motion using straightforward technology. Extensive simulations of the wave energy concept are presented, along with results from the experimental setup of a multisided permanent magnet linear generator. The prototype is designed through systematic electromagnetic field calculations. The experimental results are used for the verification of measurements in the design process of future full-scale direct wave energy converters. The present paper, describes the energy conversion concept from a system perspective, and also discusses the economical and some environmental considerations for the project.

  • 52.
    Lindblom, Adam
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Isberg, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Bernhoff, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Leijon, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    An inductive 700 MW high voltage pulse generator2006In: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 34, no 5, p. 1838-1845Article in journal (Refereed)
    Abstract [en]

    A repetitive inductive 700-MW high-voltage pulsegenerator that delivers a 150-ns square pulse with 20-ns rise timeat 150 kV has been constructed. The pulse generator has a 1:10 aircore transformer connected to a 25-Ω pulse forming line (PFL).The transformer and the PFL are both constructed using highvoltagecables. The closing switch of the PFL is a spark gap thatis in a water tank together with the cable endings of the PFL andtransformer. The electric field at the cable endings is refractivelygraded by the high permittivity of the surrounding water. ThePFL is charged in 2.5 μs to 170 kV, and the electric field in theclosing switch of the PFL reaches 33 kV/mm until the thresholdvoltage is exceeded. The efficiency of the pulse generator is 40%.The authors believe that this concept can be up-scaled to a 25-GWgenerator operating at 500 kV. An electric circuit simulation ofa 25-GW pulse generator and an electrostatic simulation for arefractive cable ending are presented.

  • 53.
    Liu, Yaqing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Theethayi, Nelson
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Thottappillil, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    A Non-Uniform Transmission Line Approach for Transient Analysis of Grounding System underLightning Impulse2004In: Proc. of the 27th International Conference on Lightning Protection, 2004, no paper No. 149Conference paper (Refereed)
  • 54.
    Liu, Yaqing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Theethayi, Nelson
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Thottappillil, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    An Engineering Model for Transient Analysis of Grounding System Under Lightning Strikes: Nonuniform Transmission-Line Approach2005In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 20, no 2, p. 722-730Article in journal (Refereed)
    Abstract [en]

    A nonuniform transmission line approach is adopted in this paper for modeling the transient behavior of different types of grounding systems under lightning strikes in time domain by solving Telegrapher's equations based on finite-difference time-domain (FDTD) technique. Electromagnetic couplings between different parts of the grounding wires are included using effective per-unit length parameters (l, c, and g), which are space and time dependent. The present model can predict both the effective length and the transient voltage of grounding electrodes accurately, while, an uniform transmission line approach with electrode length dependent per-unit length parameters fails to predict the same. Unlike the circuit theory approach , the present model is capable of predicting accurately the surge propagation delay in the large grounding system. The simulation results for buried horizontal wires and grounding grids based on the present model are in good agreement with that of the circuit and electromagnetic field approaches , . From an engineering point of view, the model presented in this paper is sufficiently accurate, time efficient, and easy to apply.

  • 55.
    Liu, Yaqing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Theethayi, Nelson
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Thottappillil, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Investigating the validity of existing definitions and empirical equations of effective length/area of grounding wire/grid for transient studies2007In: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 65, no 5-6, p. 329-335Article in journal (Refereed)
    Abstract [en]

    There are various definitions for effective length/area of grounding wire/grid for lightning transients [A.S. Farag, T.C. Cheng, D. Penn, Grounding terminations of lightning protective systems, IEEE Trans. Dielectics, Elect. Insul 5(6) (1998) 869–877; B.R. Gupta, B. Thapar, Impulse impedance of grounding grid, IEEE Trans. Power Apparatus Syayem PAS-99(6) (1980) 2357–2362; Y. Liu, N. Theethayi, R. Thottappillil, An engineering model for transient analysis of grounding system under lightning strikes: non–uniform transmission line approach. IEEE Trans. Power Delivery 20 (2) (2005) 722–730; M.I. Lorentzou, N.D. Hatziargriou, Modelling of long grounding conductors using EMTP, in: IPST’99, International Conference on Power System Transients, Budapest, 20–24 June, 1999; L.D. Grcev, M. Heimbach, Frequency dependent and transient characteristics of substation grounding system, IEEE Trans. Power Delivery 12 (1997) 172–178.]. The present work investigates and discusses the validity of those existing definitions. Further, practical methods for estimating the effective length/area of different grounding structures are proposed for engineering applications. The calculations for effective length/area based on non-uniform transmission line approach (Liu et al., 2005) show that, for a single grounding wire, the empirical equation for effective length in Farag et al. (1998) is not valid when the injection current has very fast rise time. Also, the empirical equation for effective length of grid edge in Gupta and Thapar (1980) is not applicable for grids with large inner mesh size.

  • 56.
    Liu, Yaqing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Theethayi, Nelson
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Thottappillil, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Gonzalez, Raul
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Zitnik, Mihael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    An improved model for soil ionization around grounding system and its application to stratified soil2004In: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 60, no 2-4, p. 203-209Article in journal (Refereed)
    Abstract [en]

    An improved model for taking into account the effect of the soil ionization around grounding system under lightning strike is proposed in this paper. In this model, the soil ionization region is assumed to retain 7% of its pre-ionization resistivity, which is consistent with the experimental results on soil ionization found in literature (Trans. SA Inst. Electr. Eng. (1988) 63; AIEE Trans. 61 (1942) 349; Proc. IEE 121(2) (1974) 123) and our own laboratory experiments (Time domain modelling of the response of grounding systems subjected to lightning currents, Licenciate Thesis, Uppsala University, 2003). Compared with modelling the soil ionization as an increase in the size of the ground conductor, the model presented here will not overestimate the beneficial influence of the soil ionization in reducing the ground potential rise, especially in high resistivity soil. The model is also applied to study the transient behaviour of grounding conductors in stratified soil under lightning strike including soil ionization. It shows that making the grounding conductor to penetrate the lower resistivity soil layer could help to decrease the ground potential rise at the injection point several times.

  • 57.
    Lundström, Ludvig
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Gustavsson, R.
    Aidanpää, J.-O
    Luleå tekniska universitet.
    Dahlbäck, Niklas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Leijon, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Influence on the stability of generator rotors due to radial and tangential magnetic pull force2007In: IET Electric Power Applications, ISSN 1751-8660, Vol. 1, no 1, p. 1-8Article in journal (Refereed)
    Abstract [en]

    Forces due to nonuniform airgaps in rotating electrical machines have been a researchtopic for over 100 years. However, most research in the area of rotating electrical machines hasbeen performed on motors. Large forces in hydropower generators can lead to expensive damageand failures. Therefore, it is of interest to calculate the forces that arise in a large synchronousgenerator with an eccentric rotor and study the influence these forces have on the stability of thegenerator rotor. A 74 MVA synchronous hydropower generator was simulated with an eccentricrotor, using a time-stepping finite-element technique. The forces were calculated using Coulomb’svirtual-work method and simulations were performed for no-load and load cases. The resultingforce was found to be reduced significantly when a damper winding was taken into account. Aninteresting effect of the rotor damper winding was that it reduced the eccentricity force andintroduced a force component perpendicular to the direction of eccentricity. The results from thefinite-element simulations were used to determine how the forces affect the stability of the generatorrotor. Damped natural eigenfrequencies and damping ratio for load and no-load conditions arepresented. When applying the forces computed in the time-dependent model, the damped naturaleigenfrequencies were found to increase and the stability of the generator rotor was found to bereduced compared with when the forces were computed in a stationary model.

  • 58.
    Manyahi, Mighanda
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Characteristic of Surge Transfer Through Transformers: Study of Conventional Distribution Transformer and XLPE Cable Winding Transformer (Dryformer)2002Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Wide spread application and dependence on microelectronics based equipment in modern society has necessitated the study of power supply quality problems in low voltage power installations. In spite of improvements in surge protection, sensitive equipment connected to low-voltage side of distribution transformer has continued to fail due to transient voltages that are transferred through distribution transformer from high voltage circuits. Furthermore, the failures of distribution transformer primary winding due to lightning induced transients entering through unprotected low voltage (secondary) winding has been a subject of concern in recent years. Also the recent advent of XLPE cable winding transformer (Dryformer) that performs one step transformation from transmission to distribution voltage levels has introduced new challenges in our understanding of the transfer of transient surges between the transmission and distribution circuits. The knowledge of the signatures of transient surge voltages transferred between the distribution transformer and Dryformer circuits is essential for the evaluation of the transformer transient response, and hence, for devising appropriate protective methods. This thesis studies the transient response of distribution transformer and Dryformer, and provides an advanced understanding of transient overvoltage transfer between the circuits of these transformers.

    Transient response of distribution transformer and Dryformer are studied by laboratory experiments, with consideration of surges that have various steepness, amplitude and duration characteristics, replica of surges that are expected in practise. The differences between these transformer designs on transient responses are discussed in perspective of their basic difference in construction and winding design features. Simplified procedure for the formulation of transformer model suitable for simulating the transferred transient voltages is developed. The model is formulated based on terminal measurements of transfer and driving point short circuit admittance parameters, as elements of the nodal admittance matrix, obtained by either frequency domain or time domain measurements. The nodal admittance matrix elements are simultaneously approximated in the form of rational functions by vector fitting and admittance functions in the form of RLCG networks are realised. Ultimately, the high frequency transformer terminal model is created as a π-network consisting of the above RLCG networks for each of its branches, suitable for use in circuit simulation program in time domain. The realised model has an upper-frequency bandwidth of 3 MHz. The model validity is verified by comparing the model predictions with experimentally obtained responses, and it has been successfully applied in predicting the surge transfer between the transformer circuits due to various types of surges. Experiment and model prediction results shows that the characteristics of the transferred surge voltage depend both on the characteristics of the applied surge and on whether it is from primary to secondary or vice versa. The procedure for model formulation is general enough to be adapted for any two port devices that behave linearly in the frequency range of interest.

  • 59. Moiseenko, V. E.
    et al.
    Ågren, Olov
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Second harmonic cyclotron heating of sloshing ions in a straight field line mirror2007In: Fusion science and technology, ISSN 1536-1055, E-ISSN 1943-7641, Vol. 51, no 2T, p. 160-163Article in journal (Refereed)
    Abstract [en]

    The second harmonic heating in mirrors is explicated. A new coordinate-independent form of the second harmonic term in the plasma dielectric response is derived. The second harmonic heating in the WKB limit is addressed and compared with minority heating. A newly developed three-dimensional model for the time-harmonic boundary problem for Maxwell's equations is used for second harmonic heating modeling in the reactor-scale straight field line mirror device. Computations show that the antenna Q is low and the regime of global resonance overlapping is in effect. Only a small portion of the wave energy transits through the cyclotron layer and penetrates to the central part of the trap. The power deposition is peaked at the plasma core.

  • 60.
    Moiseenko, Vladimir E.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Ågren, Olov
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    A numerical model for radiofrequency heating of sloshing ions in a mirror trap2006In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 72, no 6, p. 1133-1137Article in journal (Refereed)
    Abstract [en]

    A newly developed numerical model calculating the distribution and damping of radiofrequency fields by sloshing ions is presented. The model solves time-harmonic Maxwell's equations written in terms of the electric field. It uses a two-dimensional grid and a Fourier series in the third coordinate and is based on a non-staggered mesh not aligned along the steady magnetic field. The numerical stability of the scheme is discussed, and the convergence analysis is presented.

  • 61.
    Moiseenko, Vladimir E.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Ågren, Olov
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Second harmonic ion cyclotron heating of sloshing ions in a straight field line mirror2007In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 14, no 2, p. 022503-Article in journal (Refereed)
    Abstract [en]

    A qualitative analysis of second harmonic heating is carried out, in which a fast magnetosonic wave is launched from a location near the magnetic mirror (where the magnetic field is stronger than the second harmonic resonance field) and directed to the midplane of the open trap. The analysis shows that there is no "magnetic beach" heating in contrast to the case with minority heating on the fundamental harmonic. Conversion to the ion Bernstein wave would distort the heating pattern, and the condition for this conversion is estimated. The scenario of second harmonic heavy ion heating is examined numerically. In the scenario chosen, the regime of global resonance overlapping is achieved that provides good heating performance. The computations show that the power deposition is core, the amount of deposited power does not depend sensitively on the parameters of the discharge, and the range of plasma beta at which the heating is efficient is not narrow. The estimated antenna Q is noticeably low and, therefore, the antenna performance is high.

  • 62.
    Montaño, Raul
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    The Effects of Lightning on Low Voltage Power Networks2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The present society is highly dependant on complex electronics systems, which have a low damage threshold level. Therefore, there is a high risk of partial or total loss of the system’s electronics when they are exposed to a thunderstorm environment. This calls for a deep understanding on the mechanism related to the interaction of lightning generated electromagnetic fields with various large distributed/scattered systems. To accurately represent the interaction of lightning electromagnetic fields with electrical networks, it is necessary to have return stroke models capable to reproduce the electromagnetic field signatures generated by a lightning flash. Several models have been developed in the recent past to study the field-to-wire coupling mechanism. The most popular, simple and accurate among the available models is the Agrawal et al. model. On the other hand, ATP-EMTP is a well-known transient simulation package widely used by power engineers. This package has various built-in line models like Semlyen, Marti and Noda setups. There is a difficulty in applying the Agrawal et al. model with the built-in line models of ATP-EMTP, as the voltage source due to the horizontal component of electric field in Agrawal et al. model is in series with the line impedance and not in between two transmission line segments. Furthermore, when the electromagnetic field is propagating over a finite conducting ground plane, the soil will selectively attenuate the high frequency content of the electromagnetic field; causing a change in the field wave shape. A finite conducting ground will also produce a horizontal field component at the ground level. Several approximations are available in the literature to obtain the horizontal electric field; namely the wave-tilt and the Cooray-Rubinstein approximation. Consequently, it is important to investigate the change on the induced voltage signature when the power line is located over a finitely conducting ground. Additionally, to provide protection from lightning induced transients it is necessary to use Surge Protective Devices (SPDs) capable of diverting the incoming transients and provide protection level necessary to avoid damage in the equipment. However, standard test procedures of the SPDs do not take into account sub-microsecond structure of the transients. Therefore, to provide the required protection level to sensitive equipments connected to the low voltage power network, it is essential to understand the response of SPDs subjected to high current derivative impulses. This thesis is aimed to investigate the research problems as addressed above. Special attention will be given to a new proposed return stroke model, a simple circuit approach for efficient implementation of Agrawal et al. model using ATP-EMTP, the effect of the soil conductivity on the lightning induced overvoltage signatures and the response of surge protective devices subjected to high current derivative impulses.

    List of papers
    1. A model to represent negative and positive lightning first strokes with connecting leaders
    Open this publication in new window or tab >>A model to represent negative and positive lightning first strokes with connecting leaders
    2004 (English)In: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 60, no 2-4, p. 97-109Article in journal (Refereed) Published
    Abstract [en]

    A channel base current model of the current generation (CG) type is introduced to describe both negative and positive first return strokes. The key feature of the model is the association of the slow front of the channel base current waveform with the upward connecting leader. This feature is mathematically represented by a discharge propagation speed profile, which is characterized by an initial exponential increase with increasing height. It is shown that the previous models of the CG type may be incapable of reproducing adequately the observed electromagnetic fields when the channel base current contains a slow front.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-93861 (URN)10.1016/j.elstat.2004.01.016 (DOI)
    Available from: 2005-12-16 Created: 2005-12-16 Last updated: 2017-12-14Bibliographically approved
    2. On the Implementation of Agrawal et al. Model for Lightning Induced Voltage Calculations Using ATP-EMTP
    Open this publication in new window or tab >>On the Implementation of Agrawal et al. Model for Lightning Induced Voltage Calculations Using ATP-EMTP
    In: IEEE Transaction on Power DeliveryArticle in journal (Refereed) In press
    Identifiers
    urn:nbn:se:uu:diva-93862 (URN)
    Available from: 2005-12-16 Created: 2005-12-16 Last updated: 2010-01-14Bibliographically approved
    3. Lightning Induce Over voltage: Comparison of two analytical formulation
    Open this publication in new window or tab >>Lightning Induce Over voltage: Comparison of two analytical formulation
    Manuscript (Other academic)
    Identifiers
    urn:nbn:se:uu:diva-93863 (URN)
    Available from: 2005-12-16 Created: 2005-12-16 Last updated: 2010-01-13Bibliographically approved
    4. Penetration of lightning induced transient from high voltage to low voltage power system across distribution transformers
    Open this publication in new window or tab >>Penetration of lightning induced transient from high voltage to low voltage power system across distribution transformers
    2004 (English)In: Proceeding of the 27th International Conference on Lightning Protection, 2004Conference paper, Published paper (Refereed)
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-93864 (URN)
    Conference
    27th International Conference on Lightning Protection, 13-16 sept, 2004, Avignon, France
    Available from: 2005-12-16 Created: 2005-12-16 Last updated: 2013-09-24Bibliographically approved
    5. Transient response of DC Converter station subjected to LIOV
    Open this publication in new window or tab >>Transient response of DC Converter station subjected to LIOV
    2005 (English)In: Proceeding of the VIII International Symposium on Lightning Protection, 2005Conference paper, Published paper (Refereed)
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-93865 (URN)
    Conference
    The VIII International Symposium on Lightning Protection- SIPDA, 21-25 nov, 2005, São Paulo, Brasil
    Available from: 2005-12-16 Created: 2005-12-16 Last updated: 2013-09-18Bibliographically approved
    6. Induced over voltage sensitivity analysis using STIDDA
    Open this publication in new window or tab >>Induced over voltage sensitivity analysis using STIDDA
    In: Proceeding of the 26th International Conference on Lightning ProtectionArticle in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-93866 (URN)
    Available from: 2005-12-16 Created: 2005-12-16Bibliographically approved
    7. Measurements of Lightning Transients Entering a Swedish Railway Facility
    Open this publication in new window or tab >>Measurements of Lightning Transients Entering a Swedish Railway Facility
    Show others...
    2004 (English)In: Proceedings of 27th International Conference on Lightning Protection, 2004Conference paper, Published paper (Other academic)
    Keywords
    Lightning Protection, Electromagnetic Compatibility
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-93867 (URN)
    Conference
    27th International Conference on Lightning Protection, 13-16 sept, 2004, Avignon, France
    Available from: 2005-12-16 Created: 2005-12-16 Last updated: 2013-09-24Bibliographically approved
    8. Resistance Of Spark Channels
    Open this publication in new window or tab >>Resistance Of Spark Channels
    Show others...
    2006 (English)In: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 34, no 5, p. 1610-1619Article in journal (Refereed) Published
    Abstract [en]

    A study undertaken to measure the resistance of spark channels in air with two different current waveforms is presented. In one experiment, the spark was created by a Marx generator. In this case, the gap length was maintained at 12.8 cm, and the current flowing through the spark had a peak current lying in the range of 0.2-2.2 kA. The decay time of the current was larger than 100 mus. In the other experiment, the spark was created by a current generator. In that experiment, the gap length was maintained at 1 cm, and the current flowing through the spark had peak-current amplitudes in the range of 35-48 kA. The decay time of the current was larger than 500 mus. The results show that the resistance of spark channels initially decreases, reaches a minimum value, and then recovers as the current in the spark gap decreases. The minimum resistance of the spark channel decreases with an increasing peak current. The results are compared with various theories that attempt to predict the temporal variation of the resistance of spark channels. The comparison shows that further developments in the existing theoretical models are needed in order to reproduce with better accuracy the dynamic behavior of the channel resistance

    National Category
    Meteorology and Atmospheric Sciences Engineering and Technology
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-93868 (URN)10.1109/TPS.2006.883350 (DOI)
    Available from: 2005-12-16 Created: 2005-12-16 Last updated: 2017-12-14
    9. Varistor models: a comparison between theory and practice
    Open this publication in new window or tab >>Varistor models: a comparison between theory and practice
    2004 (English)In: Proceeding of the 27th International Conference on Lightning Protection, 2004Conference paper, Published paper (Refereed)
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-93869 (URN)
    Conference
    International Conference on Lightning Protection, 13-16 sept, 2004, Avignon, Frankrike
    Available from: 2005-12-16 Created: 2005-12-16 Last updated: 2013-09-18Bibliographically approved
    10. Response of Low Voltage Surge Protective Devices to Current Impulses with High Time Derivatives
    Open this publication in new window or tab >>Response of Low Voltage Surge Protective Devices to Current Impulses with High Time Derivatives
    In: IEEE Transaction on EMCArticle in journal (Refereed) In press
    Identifiers
    urn:nbn:se:uu:diva-93870 (URN)
    Available from: 2005-12-16 Created: 2005-12-16 Last updated: 2010-01-14Bibliographically approved
  • 63.
    Montaño, Raul
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Becerra, Marley
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Rahman, Mahbubur
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Liyanage, Prasanna
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Resistance Of Spark Channels2006In: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 34, no 5, p. 1610-1619Article in journal (Refereed)
    Abstract [en]

    A study undertaken to measure the resistance of spark channels in air with two different current waveforms is presented. In one experiment, the spark was created by a Marx generator. In this case, the gap length was maintained at 12.8 cm, and the current flowing through the spark had a peak current lying in the range of 0.2-2.2 kA. The decay time of the current was larger than 100 mus. In the other experiment, the spark was created by a current generator. In that experiment, the gap length was maintained at 1 cm, and the current flowing through the spark had peak-current amplitudes in the range of 35-48 kA. The decay time of the current was larger than 500 mus. The results show that the resistance of spark channels initially decreases, reaches a minimum value, and then recovers as the current in the spark gap decreases. The minimum resistance of the spark channel decreases with an increasing peak current. The results are compared with various theories that attempt to predict the temporal variation of the resistance of spark channels. The comparison shows that further developments in the existing theoretical models are needed in order to reproduce with better accuracy the dynamic behavior of the channel resistance

  • 64.
    Montaño, Raul
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Induced over voltage sensitivity analysis using STIDDAIn: Proceeding of the 26th International Conference on Lightning ProtectionArticle in journal (Refereed)
  • 65.
    Montaño, Raul
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Penetration of lightning induced transient from high voltage to low voltage power system across distribution transformers2004In: Proceeding of the 27th International Conference on Lightning Protection, 2004Conference paper (Refereed)
  • 66.
    Montaño, Raul
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Edirisinghe, Mahesh
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Roman, Francisco
    Behavior of low-voltage surge protective devices under high-current derivative impulses2007In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 22, no 4, p. 2185-2190Article in journal (Refereed)
    Abstract [en]

    It has been observed by scientists that maximum rate of change of current with respect to time of subsequent return strokes could be as high as 150 kA/mu s. This fact is not reflected in the present day testing of surge protecting devices (SPDs). Usually, they are tested with 8/20 mu s current impulses the time derivative of which are considerably less than the time derivatives of subsequent-return stroke current pulses. When SPDs are subjected to current impulses with a high-current derivative, the voltage yields on their terminals will be highly influenced by the inductance of the lead connections. Therefore, a high di/dt impulse current can produce a voltage across the SPDs terminals that can exceed the threshold level of the protected equipment, causing partial or permanent damage in their insulation. In this study, the behavior of few selected surge protective components for fast current transients is analyzed and compared with standard 8/20 mu S current impulses. The experiment was performed on disk type varistors and ceramic type gas discharge tubes (GDT). The result show that, the clamping voltages due to fast transients for tested component is considerably greater than the ones observed with standard 8/20 mu S current impulses.

  • 67.
    Montaño, Raul
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Edirisinghe, Mahesh
    Cooray, Vernon
    Roman, Francisco
    Response of Low Voltage Surge Protective Devices to Current Impulses with High Time DerivativesIn: IEEE Transaction on EMCArticle in journal (Refereed)
  • 68.
    Montaño, Raul
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Edirisinghe, Mahesh
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Roman, Francisco
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Varistor models: a comparison between theory and practice2004In: Proceeding of the 27th International Conference on Lightning Protection, 2004Conference paper (Refereed)
  • 69.
    Montaño, Raul
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Edirisinghe, Mahesh
    Fernando, Mahendra
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Transient response of DC Converter station subjected to LIOV2005In: Proceeding of the VIII International Symposium on Lightning Protection, 2005Conference paper (Refereed)
  • 70.
    Montaño, Raul
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Theethayi, Nelson
    Cooray, Vernon
    Lightning Induce Over voltage: Comparison of two analytical formulationManuscript (Other academic)
  • 71.
    Montaño, Raul
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Theethayi, Nelson
    Cooray, Vernon
    On the Implementation of Agrawal et al. Model for Lightning Induced Voltage Calculations Using ATP-EMTPIn: IEEE Transaction on Power DeliveryArticle in journal (Refereed)
  • 72. Mäkelä, J. S.
    et al.
    Edirisinghe, M.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Fernando, M.
    Montaño, Raul
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    HF radiation emitted by chaotic leader processes2007In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 69, no 6, p. 707-720Article in journal (Refereed)
    Abstract [en]

    This paper presents direct measurements of narrowband 10 MHz HF radiation from so-called "chaotic leaders" associated with subsequent return strokes. Although the term is controversial and poorly defined, we find that more than 30% of subsequent strokes in close lightning flashes contain electric field characteristics that are best described as "chaotic". In earlier studies, return strokes have consistently been observed to be the strongest sources of HF radiation, but the results for leader processes are less consistent. We also observe return strokes to be the main HF emitter, and the leaders before the first return stroke in a flash sequence also emit HF though somewhat less intensely. The leaders preceding subsequent strokes typically emit little or no HF radiation, whether they are dart or dart-stepped leaders. However, it was observed that the presence of a chaotic component increases the leader HF intensity dramatically Defining the HF intensity unequivocally can be problematic for processes like chaotic leaders which have a combination of continuous and impulsive phenomena. Two time-domain methods were used to measure the HF intensity, the peak energy and the RMS energy. In the frequency domain these correspond to the energy spectral density (ESD) and power spectral density (PSD), respectively. It was found that the methods are not necessarily compatible. Thus, it is suggested that to clarify future work, leader processes should be characterized by the PSD rather than the ESD.

  • 73.
    Månsson, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Nilsson, Tony
    Thottappillil, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Bäckström, Mats
    Susceptibility of GPS Receivers and Wireless Cameras to a single Radiated UWB Pulse2006In: Proceedings of EMC EuropeArticle in journal (Refereed)
  • 74. Nilsson, Karin
    et al.
    Danielsson, Oskar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Leijon, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Electromagnetic forces in the air gap of a permanent magnet linear generator at no load2006In: Journal of Applied Physics, Vol. 99, no 3, p. 1-5Article in journal (Refereed)
  • 75.
    Nilsson, Karin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Danielsson, Oskar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Leijon, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Electromagnetic forces in the air gap of a permanent magnet linear generator at no-load2006In: Journal of Applied Physics, Vol. 99, no 3, p. 034505 1-5Article in journal (Refereed)
  • 76.
    Nilsson, Karin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Segergren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Leijon, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Concept of a Direct Drive Permanent Magnetized Generator for Experimental Verification of Marine Current Power Conversion: Proposed Experimental Setup2005In: Proceedings from the 24th International Conference on Offshore Mechanics and Arctic Engineering - OMAE 2005, 2005, p. 3-Conference paper (Refereed)
  • 77.
    Nilsson, Karin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Segergren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Leijon, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Simulation of Direct Drive Generators Designed for Underwater Vertical Axis Turbines2003In: Proceedings from the Fifth European Wave Energy Conference, September 2003, 2003, p. 6-Conference paper (Other academic)
  • 78.
    Nilsson, Karin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Segergren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Sundberg, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Sjöstedt, Elisabeth
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Leijon, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Converting kinetic energy in small watercourses using direct drive generators2004Conference paper (Refereed)
  • 79. Perera, C.
    et al.
    Fernando,, M.
    Liyanage,, P.
    Rahman,, Mahbubur
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Correlation between current and channel diameter of long laboratory sparks2008In: 29th International Conference on Lightning Protection, ICLP-2008, Uppsala, Sweden, June 23-26, 2008Conference paper (Refereed)
  • 80.
    Rahman, M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, V.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    NOx Production in Laser -Induced Plasma as a Function of Dissipated Energy2003In: EOS Trans. AGU, 84(46), Fall Meet. Suppl., Abstract AE32A-0158, 2003, San Francisco, USA, 2003Conference paper (Other academic)
  • 81.
    Rahman, M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Thottappillil, R.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Berg, M.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Hillborg, H.
    Surface Charge and Hydrophobicity Levels of Insulating Materials2001In: 12th Int. Symp. on High Voltage Engineering, ISH-2001, Bangalore, India, August 20-24, p628-631,, 2001, p. 628-631Conference paper (Refereed)
  • 82.
    Rahman, Mahbubur
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    NOx Production by Ionisation Processes in Air2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The study presented in this thesis was motivated by the large uncertainty on the concentration of atmospheric electrical discharges to the global nitrogen budget. This uncertainty is partly due to the fact that information concerning the NOx production efficiency of electrical discharges having current signatures similar to those of lightning flashes is not available in the literature. Another reason for this uncertainty is the fact that energy is used as a figure of merit in evaluating NOx production from lightning flashes even though insufficient knowledge is available concerning the energy dissipation in lightning flashes. The third reason for this uncertainty is the lack of knowledge concerning the contribution of discharge processes other than return strokes to the NOx production in the atmosphere. Lightning is not the only process in the atmosphere that causes ionisation and dissociation of atmospheric air. Cosmic rays continuously bombard the Earth with high energetic particles and radiation causing ionization and dissociation of air leading to the production of NOx in the atmosphere. The work carried out in this thesis is an attempt to improve the current knowledge on the way in which these processes contribute to the global NOx production. Experiments have been conducted in this thesis to estimate the NOx production efficiency of streamer discharges, laser-induced plasma, laboratory sparks having current signatures similar to those of lightning flashes, alpha particle impact in air and finally with the lightning flash itself. The results obtained from laboratory electrical discharges show the following: (a) The NOx production efficiency, in terms of energy, of positive streamer discharges is more or less similar to those of hot discharges. (b) The NOx production efficiency of an electrical discharge depends not only on the energy but also on the peak and the shape of the current waveform. (c) The current signature is a better figure of merit in evaluating the NOx yield of electrical discharges. As a part of this thesis work a direct measurement of NOx generated by lightning flashes was conducted and the results show that slow discharge processes such as continuing currents could be the main source of NOx in lightning flashes. Concerning NOx production by other ionisation processes such as alpha particle impacts in the atmosphere, the data gathered in this thesis show that each ionising event in air leads to the creation of one NOx molecule. In terms of energy the NOx production efficiency of alpha particles is similar to that of electrical discharges. The theoretical studies conducted within this thesis indicate that M-components contribute more than the return strokes to the NOx production. The calculations also show that the contribution to the global NOx budget by return stroke is not as high as that assumed in the current literature.

    List of papers
    1. NOx generation in laser-produced plasma in air as a function of dissipated energy
    Open this publication in new window or tab >>NOx generation in laser-produced plasma in air as a function of dissipated energy
    2003 (English)In: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 35, p. 543-546Article in journal (Refereed) Published
    National Category
    Meteorology and Atmospheric Sciences Engineering and Technology
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-93601 (URN)10.1016/S0030-3992(03)00077-X (DOI)
    Available from: 2005-10-06 Created: 2005-10-06 Last updated: 2017-12-14
    2. A study of NOx production in air heated by laser discharges: Effect of energy, wavelength, multiple discharges and pressure
    Open this publication in new window or tab >>A study of NOx production in air heated by laser discharges: Effect of energy, wavelength, multiple discharges and pressure
    2008 (English)In: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 40, no 1, p. 208-214Article in journal (Refereed) Published
    Abstract [en]

    An experimental study on the production of NOX in air heated under the action of a concentrated laser beam is presented. In this experiment laser induced plasma was produced in air in a closed Teflon chamber of inner volume 1600 cm3 by focusing a laser beam with either the wavelength of 1064 or 532 nm from a Q-switched Nd:YAG laser. The NOX production was measured by chemiluminescence method and the possible effect of wavelengths, multiple discharges, and pressure on the yield of NOX was studied. The results show that within the studied plasma energy range of 26-253 mJ for 532 nm beam and 16-610 mJ for 1064 nm beam, the NOX production scales linearly with the dissipated plasma energy. For a given energy, 532 nm beam produces more NOX in air at atmospheric pressure than the 1064 nm beam. In an attempt to see the possible influence of multiple discharges on the production of NOX, discharges were created using 2-8 pulses with a repetition rate of 10 pulses per second in stationary air at atmospheric pressure. The results indicate that a certain amount of the NOX created by a given pulse is destroyed by the subsequent pulses. In order to study the pressure dependence of the NOX production, the pressure was varied from 16 to 100 kPa in the chamber and it was found that the NOX production efficiency scales linearly with pressure.

    Keywords
    Laser induced plasma, Lightning, Nitrogen oxides
    National Category
    Engineering and Technology Meteorology and Atmospheric Sciences
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-93602 (URN)10.1016/j.optlastec.2007.01.007 (DOI)000250258800024 ()
    Available from: 2005-10-06 Created: 2005-10-06 Last updated: 2017-12-14
    3. Efficiencies for production of NOx and O3 by streamer discharges in air at atmospheric pressure
    Open this publication in new window or tab >>Efficiencies for production of NOx and O3 by streamer discharges in air at atmospheric pressure
    2005 (English)In: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 63, p. 977-983Article in journal (Refereed) Published
    National Category
    Meteorology and Atmospheric Sciences
    Research subject
    Engineering Science with specialization in Atmospheric Discharges; Electricity, Esp The Study Of Transients and Discharges
    Identifiers
    urn:nbn:se:uu:diva-93603 (URN)
    Available from: 2005-10-06 Created: 2005-10-06 Last updated: 2017-12-14
    4. NOx production in laboratory discharges
    Open this publication in new window or tab >>NOx production in laboratory discharges
    Show others...
    2008 (English)Conference paper, Published paper (Refereed)
    National Category
    Meteorology and Atmospheric Sciences Engineering and Technology
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-93604 (URN)
    Conference
    29th International Conference on Lightning Protection, ICLP-2008, Uppsala, Sweden, June 23-26
    Available from: 2005-10-06 Created: 2005-10-06 Last updated: 2016-04-26
    5. Measurements of NOx produced by rocket-triggered lightning
    Open this publication in new window or tab >>Measurements of NOx produced by rocket-triggered lightning
    Show others...
    2007 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 34, no 3, p. L03816-Article in journal (Refereed) Published
    Abstract [en]

    We present the first direct measurements of NOx generated by specific lightning sources. In July 2005, three negative lightning flashes were triggered using the rocket-and-wire technique at the International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida. The NOx produced by these three rocket-triggered flashes was measured. The NOx production per unit charge was between 2 and 3 · 1020 molecules per meter per coulomb. The data show that the NOx production is primarily from long-duration, steady currents, as opposed to microsecondscale impulsive return stroke currents. This observation implies that cloud discharges, which transfer, via a steady current of the order of 100 A, larger charges than ground discharges, but do not contain return strokes, are as efficient as (or more efficient than) cloud-to-ground discharges in producing NOx.

     

    National Category
    Meteorology and Atmospheric Sciences Engineering and Technology
    Research subject
    Engineering Science with specialization in Atmospheric Discharges; Electricity, Esp The Study Of Transients and Discharges
    Identifiers
    urn:nbn:se:uu:diva-93605 (URN)10.1029/2006GL027956 (DOI)000244360200001 ()
    Available from: 2005-10-06 Created: 2005-10-06 Last updated: 2017-12-14
    6. On the relationship between the discharge current, energy dissipation and the NOx production in spark discharges
    Open this publication in new window or tab >>On the relationship between the discharge current, energy dissipation and the NOx production in spark discharges
    2005 (English)In: International Conference on Lightning and static Electricity, ICOLSE, Seattle, Washington, USA, September 19-23, 2005, p. PHE-44.1-Conference paper, Published paper (Refereed)
    National Category
    Engineering and Technology Meteorology and Atmospheric Sciences
    Research subject
    Electricity, Esp The Study Of Transients and Discharges; Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-93606 (URN)
    Conference
    International Conference on Lightning and Static Electricity, 19-23 September, 2005 Seattle, USA
    Available from: 2005-10-06 Created: 2005-10-06 Last updated: 2016-04-26
    7. An experimental quantification of the NOx production efficiency of energetic alpha particles in air
    Open this publication in new window or tab >>An experimental quantification of the NOx production efficiency of energetic alpha particles in air
    2006 (English)In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 68, no 11, p. 1215-1218Article in journal (Refereed) Published
    National Category
    Meteorology and Atmospheric Sciences Engineering and Technology
    Research subject
    Engineering Science with specialization in Atmospheric Discharges; Electricity, Esp The Study Of Transients and Discharges
    Identifiers
    urn:nbn:se:uu:diva-93607 (URN)10.1016/j.jastp.2006.03.003 (DOI)
    Available from: 2005-10-06 Created: 2005-10-06 Last updated: 2017-12-14
  • 83.
    Rahman, Mahbubur
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    A study of NOx production in air heated by laser discharges: Effect of energy, wavelength, multiple discharges and pressure2008In: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 40, no 1, p. 208-214Article in journal (Refereed)
    Abstract [en]

    An experimental study on the production of NOX in air heated under the action of a concentrated laser beam is presented. In this experiment laser induced plasma was produced in air in a closed Teflon chamber of inner volume 1600 cm3 by focusing a laser beam with either the wavelength of 1064 or 532 nm from a Q-switched Nd:YAG laser. The NOX production was measured by chemiluminescence method and the possible effect of wavelengths, multiple discharges, and pressure on the yield of NOX was studied. The results show that within the studied plasma energy range of 26-253 mJ for 532 nm beam and 16-610 mJ for 1064 nm beam, the NOX production scales linearly with the dissipated plasma energy. For a given energy, 532 nm beam produces more NOX in air at atmospheric pressure than the 1064 nm beam. In an attempt to see the possible influence of multiple discharges on the production of NOX, discharges were created using 2-8 pulses with a repetition rate of 10 pulses per second in stationary air at atmospheric pressure. The results indicate that a certain amount of the NOX created by a given pulse is destroyed by the subsequent pulses. In order to study the pressure dependence of the NOX production, the pressure was varied from 16 to 100 kPa in the chamber and it was found that the NOX production efficiency scales linearly with pressure.

  • 84.
    Rahman, Mahbubur
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    NOx Generation in Laser-produced Plasma as a Function of Dissipated Energy2002In: 26th International Conference on Lightning Protection, ICLP2002, Cracow, Poland, September 2-6, Vol. 2, p767-770, 2002, Vol. 2, p. 767-770Conference paper (Refereed)
  • 85.
    Rahman, Mahbubur
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    NOx generation in laser-produced plasma in air as a function of dissipated energy2003In: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 35, p. 543-546Article in journal (Refereed)
  • 86.
    Rahman, Mahbubur
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    X-ray production in laboratory discharges2007Conference paper (Other academic)
  • 87.
    Rahman, Mahbubur
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Ahmad, Noor Azlinda
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Nyberg, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Nuclear Physics.
    Rakov, V. A.
    Sharma, Sriram
    X rays from 80-cm long sparks in air2008In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 35, no 6, p. L06805-Article in journal (Refereed)
  • 88.
    Rahman, Mahbubur
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Montaño, Raùl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Liyanage, Prasanna
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Becerra, Marley
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    NOx production in laboratory discharges2008Conference paper (Refereed)
  • 89.
    Rahman, Mahbubur
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Possnert, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Ion Physics.
    Nyberg, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Nuclear and Particle Physics.
    An experimental quantification of the NOx production efficiency of energetic alpha particles in air2006In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 68, no 11, p. 1215-1218Article in journal (Refereed)
  • 90.
    Rahman, Mahbubur
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Rakov, V. A.
    X-ray Production in Laboratory Sparks in air2007Conference paper (Other academic)
  • 91.
    Rahman, Mahbubur
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Rakov, V.A.
    Uman, M.A.
    Liyanage, P
    deCarlo, B.A.
    Jerauld, J
    Rob III, R.C.
    Direct measurement of NOx produced by lightning2006In: EOS Trans. AGU, 87(52), Fall Meet. Suupl., Abstract AE53A-0289, 2006, San Francisco, USA, 2006Conference paper (Other academic)
  • 92.
    Rahman, Mahbubur
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Rakov, V.A.
    Uman, M.A.
    Liyanage, Prasanna
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    DeCarlo, B.A.
    Jerauld, J.
    Olsen III, R.C.
    Measurements of NOx produced by rocket-triggered lightning2007In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 34, no 3, p. L03816-Article in journal (Refereed)
    Abstract [en]

    We present the first direct measurements of NOx generated by specific lightning sources. In July 2005, three negative lightning flashes were triggered using the rocket-and-wire technique at the International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida. The NOx produced by these three rocket-triggered flashes was measured. The NOx production per unit charge was between 2 and 3 · 1020 molecules per meter per coulomb. The data show that the NOx production is primarily from long-duration, steady currents, as opposed to microsecondscale impulsive return stroke currents. This observation implies that cloud discharges, which transfer, via a steady current of the order of 100 A, larger charges than ground discharges, but do not contain return strokes, are as efficient as (or more efficient than) cloud-to-ground discharges in producing NOx.

     

  • 93.
    Rahman, Mahbubur
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Thottappillil, R.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Berg, M.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Hillborg, H.
    Comment on 'Effect of surface charge on hydrophobicity levels of insulating materials'2002In: IEE Proceedings - Generation Transmission and Distribution, ISSN 1350-2360, E-ISSN 1359-7051, Vol. 149, no 3, p. 300-304Article in journal (Refereed)
  • 94.
    Savenko, Natalia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    MHD Stability and Confinement of Plasmas in a Single Mirror Cell2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Thermonuclear fusion is a promising energy source for the future. If an economically efficient thermonuclear reactor would be built it has to be a cheap, safe, and highly productive electric power plant, or, a heating plant.

    The emphasis of this thesis is on the single cell mirror trap with a marginally stable minimum B vacuum magnetic field, the straight field line mirror field, which provides MHD stability of the system, absence of the radial drift even to the first order in plasma β , and a reduced magnetic flux tube ellipticity. Strong density depletion at the mirrors is proposed as a mean to build up a strong potential barrier for the electrons and thereby increase the electron temperature. Conditions to obtain an energy gain factor Q>10 are briefly analyzed. Current coils which could generate the derived magnetic field are proposed. A sloshing ion distribution function is constructed for the three dimensional ‘straight line mirror field’. The gyro centre Clebsch coordinates are found to be a new pair of motional invariants for this magnetic field. The gyro centre Clebsch coordinate invariants can be used to obtain complete solutions of the Vlasov equation, including the diamagnetic drift. These solutions show that the equilibria satisfy the locally omniginuity criterion to the first order in β .

    Contributions of the plasma diamagnetism to the magnetic flux tube ellipticity are studied for the straight field line mirror vacuum magnetic field and a sloshing ion distribution. Computations employing ray tracing have shown that there is a modest increase in the ellipticity, but the effect is small if β <0.2 .

    Adiabatic charged particle motion in general field geometry has been studied. A set of four independent stationary invariants, the energy, the magnetic moment, the radial drift invariant, and the bounce average parallel velocity is proposed to describe adiabatic equilibria.

    List of papers
    1. Magnetic mirror minimum B field with optimal ellipticity
    Open this publication in new window or tab >>Magnetic mirror minimum B field with optimal ellipticity
    2004 In: Physics of Plasmas, Vol. 11, no 11, p. 5041-5045Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-94152 (URN)
    Available from: 2006-03-21 Created: 2006-03-21Bibliographically approved
    2. Theoretical study of increased electron temperature in mirror machines by tuned ion cyclotrin resonance heating cycles
    Open this publication in new window or tab >>Theoretical study of increased electron temperature in mirror machines by tuned ion cyclotrin resonance heating cycles
    2005 In: Physics of Plasmas, Vol. 12, no 2, p. 022506-1-022506-10Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-94153 (URN)
    Available from: 2006-03-21 Created: 2006-03-21Bibliographically approved
    3. Minimum B field with optimal ellipticity and idea for improved axial confinement by tuned ICRH cycles
    Open this publication in new window or tab >>Minimum B field with optimal ellipticity and idea for improved axial confinement by tuned ICRH cycles
    2005 In: Transactions of Fusion Science and Technology, ISSN 1536-1055, Vol. 47, no 1T, p. 285-287Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-94154 (URN)
    Available from: 2006-03-21 Created: 2006-03-21Bibliographically approved
    4. Rigid rotation symmetry of a marginally stable minimum B field and analytical expressions of the flux coordinates
    Open this publication in new window or tab >>Rigid rotation symmetry of a marginally stable minimum B field and analytical expressions of the flux coordinates
    2005 In: Physics of Plasmas, Vol. 12, no 4, p. 042505-1-042505-5Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-94155 (URN)
    Available from: 2006-03-21 Created: 2006-03-21Bibliographically approved
    5. Sloshing ion distribution function in a minimum B mirror field
    Open this publication in new window or tab >>Sloshing ion distribution function in a minimum B mirror field
    2005 In: Physics of Plasmas, Vol. 12, no 2, p. 022504-1-022504-5Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-94156 (URN)
    Available from: 2006-03-21 Created: 2006-03-21Bibliographically approved
    6. Constants of motion in a minimum B mirror magnetic field
    Open this publication in new window or tab >>Constants of motion in a minimum B mirror magnetic field
    2005 In: Physical Rewiev E, Vol. 72, no 2, p. 026408-1-026408-5Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-94157 (URN)
    Available from: 2006-03-21 Created: 2006-03-21Bibliographically approved
    7. Theory of the staight field line mirror
    Open this publication in new window or tab >>Theory of the staight field line mirror
    2005 In: Conference Proceedings of the 32nd EPS Plasma Physics Conference in Tarragona, Spain, Vol. 29C, p. P. - 4.069Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-94158 (URN)
    Available from: 2006-03-21 Created: 2006-03-21Bibliographically approved
    8. Finite beta correction to the magnetic flux tube ellipticity of the straight field line mirror
    Open this publication in new window or tab >>Finite beta correction to the magnetic flux tube ellipticity of the straight field line mirror
    2006 (English)In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 13, no 12, p. 122504-Article in journal (Refereed) Published
    Abstract [en]

    A marginal minimum B mirror magnetic field has been proposed as an external plasma confining magnetic field for a single cell open magnetic mirror trap. An analytical expression for the flux tube ellipticity of this magnetic field has in a previous study been derived with a zero plasma Β approximation. This mirror field, which consists of straight nonparallel field lines in the confinement region, has a particular interest since it is likely to correspond to the smallest possible ellipticity for a magnetohydrodynamic stable mirror confinement. The plasma current is in this paper taken into account to the first order in Β and the influence of the plasma magnetic field on the magnetic flux surface geometry is studied.

    National Category
    Physical Sciences Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-94159 (URN)10.1063/1.2401153 (DOI)000243158800024 ()
    Available from: 2006-03-21 Created: 2006-03-21 Last updated: 2017-12-14Bibliographically approved
    9. Gyro center invariant and associated diamagnetic current
    Open this publication in new window or tab >>Gyro center invariant and associated diamagnetic current
    2005 In: Physics of Plasmas, Vol. 12, no 12, p. 122503-1-122503-13Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-94160 (URN)
    Available from: 2006-03-21 Created: 2006-03-21Bibliographically approved
  • 95.
    Savenko, Natalia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Ågren, Olov
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Finite beta correction to the magnetic flux tube ellipticity of the straight field line mirror2006In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 13, no 12, p. 122504-Article in journal (Refereed)
    Abstract [en]

    A marginal minimum B mirror magnetic field has been proposed as an external plasma confining magnetic field for a single cell open magnetic mirror trap. An analytical expression for the flux tube ellipticity of this magnetic field has in a previous study been derived with a zero plasma Β approximation. This mirror field, which consists of straight nonparallel field lines in the confinement region, has a particular interest since it is likely to correspond to the smallest possible ellipticity for a magnetohydrodynamic stable mirror confinement. The plasma current is in this paper taken into account to the first order in Β and the influence of the plasma magnetic field on the magnetic flux surface geometry is studied.

  • 96.
    Segergren, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Bolund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Bernhoff, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Leijon, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Rotor Concept Comparison for Underwater Power Generation2002Conference paper (Other academic)
  • 97.
    Segergren, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Leijon, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Relation between generator geometry and resistance in armature winding2006In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 83, no 8, p. 884-892Article in journal (Refereed)
    Abstract [en]

    Resistive losses constitute a big part of the total loss in a generator, especially in low speed generators where frequency-dependent losses are low. The resistive losses in the winding are proportional to the length of the winding. In this paper, a computer-based program for generator design, using a two-dimensional finite-element method, is used to verify a theoretically-derived result, that the length of the armature winding is minimal for a specific generator geometry. A shorter armature winding might imply only a negligible improvement of the overall efficiency. The result of the computer-based design program is compared with the theoretically-derived results. A rough estimation of the relation between the length of the armature winding and the overall efficiency is included in the paper, as well as data from two existing generators.

  • 98.
    Segergren, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Nilsson, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Coiro, Dominico P
    Leijon, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Design of a very low speed PM generator for the patented KOBOLD tidal current turbine2004In: Proceedings of EnergyOcean 2004, 2004Conference paper (Refereed)
  • 99.
    Segergren, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Nilsson, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Leijon, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Permanent magnetized generator for marine current power conversion: proposed experimental setup2005In: Proceedings of OMAE2005, 2005Conference paper (Refereed)
  • 100.
    Silfverskiöld, Stefan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Effects of Lightning Electromagnetic Pulse and High Power Microwaves on Military Electric Systems2002Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The awareness of the threat posed by Lightning Electromagnetic Pulse (LEMP) and High Power Microwaves (HPM) against the operational reliability of electric systems is rapidly growing. This has led to an increasing need for reliable tools, experimental as well as theoretical, for design, analysis and verification of system immunity against electromagnetic threats. This thesis presents four main studies of electromagnetic interaction:

    Firstly, we present measurements of common-mode (CM) voltages induced in a residential low-voltage power installation (LVPI) network exposed to LEMP. The sequences of induced voltage events during the complete duration of a negative cloud-to-ground (CG) flash, a positive CG flash, and a cloud flash (CC) are presented simultaneously with the incident electric field. In addition to the return strokes in CG flashes, we found that other discharge events, notably the bipolar pulse trains associated with the initiation of both CG lightning and cloud lightning, determine the transient lightning electromagnetic environment of electric systems and components.

    Secondly, the induced voltages due to broad and narrow impulse current injection into the shield of 48 m long signal and power cables were studied in order to simulate the coupling of LEMP to shipboard cable networks. Single- and multi-point grounding were studied for proposing an appropriate grounding philosophy for ships.

    Thirdly, we have studied microwave, 0.5 to 18 GHz, field-to-wire coupling for some basic wire geometries in Anechoic Chamber (AC) and Reverberation Chamber (RC). Receiving parameters, such as the antenna receiving cross section, σw, and the effective antenna length of the wire, he, are presented. The ratio between the maximum and average values of σw may exceed 10 to 15 dB in the AC, the average being equal to σw measured in the RC. These large variations of σw measured in an AC, as a function of the direction and polarization of the incident field, imply a substantial risk for obtaining too low values of σw since, for realistic radiated susceptibility (RS) tests in an AC, only a few angles of incidence can typically be afforded. Furthermore, σw measured in the RC follows a χ2-distribution with two degrees of freedom, which it does not do in the AC.

    Fourthly, we present measurements of microwave field-to-Printed-Circuit-Board coupling for single-sided PCBs, double-sided PCBs and multi-layer PCBs performed in RC. Receiving parameters are presented. σw measured for PCBs in the RC is found to follow a χ2-distribution with two degrees of freedom. The impedance-matched σw is bounded by λ2/8π. he of the traces on the PCBs is found to be roughly bounded by the wavelength λ.

123 51 - 100 of 137
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