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Gustafsson, Stefan
Publications (10 of 14) Show all publications
Nordebo, S., Cinar, G., Gustafsson, S. & Nilsson, B. (2015). Dispersion modeling and analysis for multilayered open coaxial waveguides. IEEE transactions on microwave theory and techniques, 63(6), 1791-1799
Open this publication in new window or tab >>Dispersion modeling and analysis for multilayered open coaxial waveguides
2015 (English)In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 63, no 6, p. 1791-1799Article in journal (Refereed) Published
Abstract [en]

This paper presents a detailed modeling and analysis regarding the dispersion characteristics ofmultilayered open coaxial waveguides or cables. The electromagnetic model is based on a layer recursive computation of axial-symmetric fields in connection with a magnetic frill generator excitation that can be calibrated to the current measured at the input of the cable. The layer recursive formulation enables a stable and efficient numerical computation of the related dispersion functions, as well as a detailed analysis regarding the analytic and asymptotic properties of the associated determinants. Modal contributions as well as the contribution from the associated branch-cut (nondiscrete radiating modes) are defined and analyzed. Measurements and modeling of pulse propagation on an 82-km-long HVDC power cable are presented as a concrete example. In this example, it is concluded that the contribution from the dominating axial-symmetric transverse magnetic mode is sufficient, and that the contribution from the branch-cut is negligible for all practical purposes, and in particular if the exterior domain is lossy. The main contribution of this paper is to provide the necessary modeling and analysistools for a quantitative study of these phenomena.

National Category
Physical Sciences Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Technology (byts ev till Engineering)
Identifiers
urn:nbn:se:lnu:diva-40649 (URN)10.1109/TMTT.2015.2420555 (DOI)000355930300002 ()2-s2.0-84957962336 (Scopus ID)
Available from: 2015-03-07 Created: 2015-03-07 Last updated: 2017-12-04Bibliographically approved
Gustafsson, S., Nilsson, B., Nordebo, S. & Sjöberg, M. (2015). Wave propagation characteristics and model uncertainties for HVDC power cables. IEEE Transactions on Power Delivery, 30(6), 2527-2534
Open this publication in new window or tab >>Wave propagation characteristics and model uncertainties for HVDC power cables
2015 (English)In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 30, no 6, p. 2527-2534Article in journal (Refereed) Published
Abstract [en]

This paper presents a stable and efficient fullwave cable model and a detailed study of the relatedmodel uncertainties regarding the wave propagation characteristics of very long HVDC power cables at low frequencies. The model can be used to predict the dispersion characteristics of the cable with respect to its electromagnetic parameters, or as an inverse problem to estimate some parameters of the cable (armour permeability, metal layer conductivities, temperature, length, etc.) based on measurements. The electromagnetic model is based on a magnetic frill generator that can be calibrated to the current measured at the input of the cable, and a layer recursive computation of the axial-symmetric fields. Measurements of pulse propagation on an 82 km long HVDC power cable over a bandwidth of 100 kHz have been used to validate the model. The main conclusion of the study is that the conductivity (and thus the temperature) of the conductor and the lead sheath are of utmost importance to achieve an accurate model. At the same time, some parameters are in principle insignificant regarding the dispersion characteristics in the low-frequency regime, such as the permittivity and the conductivity of the semi-conducting screens. The paper contains an investigation and a discussion on the electromagnetic properties of all layers of a typical HVDC power cable.

Place, publisher, year, edition, pages
IEEE Press, 2015
National Category
Physical Sciences Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Natural Science, Physics
Identifiers
urn:nbn:se:lnu:diva-40650 (URN)10.1109/TPWRD.2015.2456237 (DOI)000365316700019 ()2-s2.0-84960844790 (Scopus ID)
Available from: 2015-03-07 Created: 2015-03-07 Last updated: 2017-12-04Bibliographically approved
Nordebo, S., Cinar, G., Gustafsson, S., Ioannidis, A. & Nilsson, B. (2014). Asymptotic analysis of non-discrete radiating modes for open waveguide structures. Mathematical methods in the applied sciences, 37(2, Special Issue), 251-256
Open this publication in new window or tab >>Asymptotic analysis of non-discrete radiating modes for open waveguide structures
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2014 (English)In: Mathematical methods in the applied sciences, ISSN 0170-4214, E-ISSN 1099-1476, Vol. 37, no 2, Special Issue, p. 251-256Article in journal (Refereed) Published
Abstract [en]

This paper presents an asymptotic analysis of non-discrete radiating modes with applications in waveguide theory. As a main application, the radiating modes of an open waveguide structure with circular geometry is considered. A generalized Jordan's lemma is used to justify that field components can be calculated as the sum of discrete and non-discrete modes, that is, as the sum of residues of poles and an integral along the branch-cut defined by the transversal wavenumber of the exterior domain. An asymptotic expression is derived for field components at large distance along the waveguide and supplemented with rigorous upper and lower error bounds. A numerical example regarding the axial symmetric 0th order transverse magnetic modes of a thin copper wire in water is included to demonstrate that there may be a non-trivial balance between the contributions from discrete and non-discrete modes.

Place, publisher, year, edition, pages
John Wiley & Sons, 2014
National Category
Engineering and Technology
Research subject
Physics, Waves and Signals
Identifiers
urn:nbn:se:lnu:diva-27488 (URN)10.1002/mma.2821 (DOI)000328520100016 ()2-s2.0-84890790594 (Scopus ID)
Available from: 2013-07-09 Created: 2013-07-09 Last updated: 2017-12-06Bibliographically approved
Gustafsson, S. (2014). Electromagnetic Dispersion Modeling and Analysis for Power Cables. (Doctoral dissertation). Växjö: Linnaeus University Press
Open this publication in new window or tab >>Electromagnetic Dispersion Modeling and Analysis for Power Cables
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis addresses electromagnetic wave propagation in power cables. It consists of five papers, where the three first papers are based on one and the same model, and the last two papers are based on a similar but slightly different model. The first model considers electromagnetic modeling in connection with basic transmission line theory with a mismatch calibration of the scattering parameters, while the second model is based on a magnetic frill generator with calibration on the input current.

The two models describe the dispersion characteristics of an 82 km long High Voltage Direct Current (HVDC) power cable, and the results are validated with Time Domain Reflectometry (TDR) measurements. In both models the relevant bandwidth is 100 kHz, with the result that the fields inside the metallic layers must be calculated due to a large skin-depth. The present study is concerned with Transversal Magnetic (TM) modes of order zero. Higher order TM modes, including the Transversal Electric (TE) modes, will essentially be cut-off in this low-frequency regime.

An asymptotic analysis regarding the low-frequency dispersion characteristics is provided in Paper I. Comparing the result with a numerical solution shows that the low-frequency characteristics of the power cable is complicated, and an asymptotic solution is only valid at frequencies below 1 Hz.

Paper II presents a sensitivity analysis of the propagation constant. It is concluded that some of the electrical parameters of the metallic layers, and of the insulating layer, have a large impact on the model, while other parameters do not perturb the model in any substantial way.

In Paper III a general framework for the electromagnetic modeling is provided. The paper addresses sensitivity analysis, computation, and measurements regarding wave propagation characteristics in power cables.

The asymptotic behavior of the non-discrete radiating mode, the branch-cut, is presented in Paper IV. The result is compared with the first and second propagating Transversal Magnetic (TM) mode.

Finally, Paper V addresses the numerical problems associated with large arguments in the Bessel functions, which are due to the large conductivity parameters of the metallic layers. The introduction of a perfect electric conductor (PEC) and a short illustration of an inverse problem are also discussed in the paper. At the end an analysis is presented regarding uncertainties in the model parameters, which shows that temperature is an important parameter to consider.

 

Place, publisher, year, edition, pages
Växjö: Linnaeus University Press, 2014
Series
Linnaeus University Dissertations ; 182/2014
Keyword
power cable, electromagnetic model, dispersion relation, asymptotic analysis, sensitivity analysis
National Category
Physical Sciences
Identifiers
urn:nbn:se:lnu:diva-40651 (URN)978-91-87925-07-8 (ISBN)
Public defence
2014-10-23, D1136, Växjö, 10:00 (English)
Opponent
Supervisors
Available from: 2015-04-28 Created: 2015-03-07 Last updated: 2015-04-28Bibliographically approved
Gustafsson, S., Biro, T., Cinar, G., Gustafsson, M., Karlsson, A., Nilsson, B., . . . Sjöberg, M. (2014). Electromagnetic dispersion modeling and measurements for HVDC power cables. IEEE Transactions on Power Delivery, 29(6), 2439-2447
Open this publication in new window or tab >>Electromagnetic dispersion modeling and measurements for HVDC power cables
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2014 (English)In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 29, no 6, p. 2439-2447Article in journal (Refereed) Published
Abstract [en]

This paper provides a general framework for electromagnetic (EM) modeling, sensitivity analysis, computation, and measurements regarding the wave propagation characteristics of high-voltage direct-current (HVDC) power cables. The modeling is motivated by the potential use with transient analysis, partial-discharge measurements, fault localization and monitoring, and is focused on very long (10 km or more) HVDC power cables with transients propagating in the low-frequency regime of about 0-100 kHz. An exact dispersion relation is formulated together with a discussion on practical aspects regarding the computation of the propagation constant. Experimental time-domain measurement data from an 80-km-long HVDC power cable are used to validate the electromagnetic model, and a mismatch calibration procedure is devised to account for the connection between the measurement equipment and the cable. Quantitative sensitivity analysis is devised to study the impact of parameter uncertainty on wave propagation characteristics. The sensitivity analysis can be used to study how material choices affect the propagation characteristics, and to indicate which material parameters need to be identified accurately in order to achieve accurate fault localization. The analysis shows that the sensitivity of the propagation constant due to a change in the conductivity in the three metallic layers (the inner conductor, the intermediate lead shield, and the outer steel armor) is comparable to the sensitivity with respect to the permittivity of the insulating layer. Hence, proper modeling of the EM fields inside the metallic layers is crucial in the low-frequency regime of 0-100 kHz.

Place, publisher, year, edition, pages
IEEE Press, 2014
National Category
Signal Processing
Research subject
Physics, Waves and Signals
Identifiers
urn:nbn:se:lnu:diva-27494 (URN)10.1109/TPWRD.2014.2324181 (DOI)000345513600003 ()2-s2.0-84913596312 (Scopus ID)
Available from: 2013-07-09 Created: 2013-07-09 Last updated: 2017-12-06Bibliographically approved
Nordebo, S., Nilsson, B., Gustafsson, S., Biro, T., Cinar, G., Gustafsson, M., . . . Sjöberg, M. (2013). Low-frequency dispersion characteristics of a multilayered coaxial cable. Journal of Engineering Mathematics, 83(1), 169-184
Open this publication in new window or tab >>Low-frequency dispersion characteristics of a multilayered coaxial cable
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2013 (English)In: Journal of Engineering Mathematics, ISSN 0022-0833, E-ISSN 1573-2703, Vol. 83, no 1, p. 169-184Article in journal (Refereed) Published
Abstract [en]

This paper provides an exact asymptotic analysis regarding the low-frequency dispersion characteristics of a multilayered coaxial cable. A layer-recursive description of the dispersion function is derived that is well suited for asymptotic analysis. The recursion is based on two well-behaved (meromorphic) subdeterminants defined by a perfectly electrically conducting (PEC) and a perfectly magnetically conducting termination, respectively. For an open waveguide structure, the dispersion function is a combination of two such functions, and there is only one branch point that is related to the exterior domain. It is shown that if there is one isolating layer and a PEC outer shield, then the classical Weierstrass preparation theorem can be used to prove that the low-frequency behavior of the propagation constant is governed by the square root of the complex frequency, and an exact analytical expression for the dominating term of the asymptotic expansion is derived. It is furthermore shown that the same asymptotic expansion is valid to its lowest order even if the outer shield has finite conductivity and there is an infinite exterior region with finite nonzero conductivity. As a practical application of the theory, a high-voltage direct current (HVDC) power cable is analyzed and a numerical solution to the dispersion relation is validated by comparisons with the asymptotic analysis. The comparison reveals that the low-frequency dispersion characteristics of the power cable is very complicated and a first-order asymptotic approximation is valid only at extremely low frequencies (below 1 Hz). It is noted that the only way to come to this conclusion is to actually perform the asymptotic analysis. Hence, for practical modeling purposes, such as with fault localization, an accurate numerical solution to the dispersion relation is necessary and the asymptotic analysis is useful as a validation tool.

Place, publisher, year, edition, pages
Springer Netherlands, 2013
National Category
Mathematics Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Physics, Waves and Signals
Identifiers
urn:nbn:se:lnu:diva-25989 (URN)10.1007/s10665-012-9616-3 (DOI)000327855300009 ()2-s2.0-84888434349 (Scopus ID)
Available from: 2013-05-31 Created: 2013-05-31 Last updated: 2017-12-06Bibliographically approved
Nordebo, S., Gustafsson, S., Ioannidis, A., Nilsson, B. & Toft, J. (2013). On the generalized Jordan's lemma with applications in waveguide theory. In: Proceeding of 2013 URSI International Symposium on Electromagnetic Theory (EMTS): International Conference Center Hiroshima, Hiroshima, Japan, May 20-24, 2013. Paper presented at International Symposium on Electromagnetic Theory (EMTS), May 20-23, 2013, Hiroshima (pp. 1039-1042).
Open this publication in new window or tab >>On the generalized Jordan's lemma with applications in waveguide theory
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2013 (English)In: Proceeding of 2013 URSI International Symposium on Electromagnetic Theory (EMTS): International Conference Center Hiroshima, Hiroshima, Japan, May 20-24, 2013, 2013, p. 1039-1042Conference paper, Published paper (Refereed)
Abstract [en]

This paper presents two variants of a generalized Jordan's lemma with applications in waveguide theory. As a main application is considered an asymptotic analysis for open waveguide structures with circular geometry. In particular, the generalized Jordan's lemma can be used to justify that field components can be calculated as the sum of discrete and non-discrete modes, i.e., as the sum of residues and an integral along the branch-cut defined by the transversal wavenumber of the exterior domain. An explicit example regarding the axial symmetric TM0 modes of a single core transmission line, wire, or optical fibre is included to demonstrate the associated asymptotic behavior for a typical open waveguide structure.

Series
URSI International Symposium on Electromagnetic Theory, ISSN 2163-405X
Keyword
Dispersion, Educational institutions, Electromagnetics, Geometry, Optical waveguides, Standards
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Physics, Waves and Signals
Identifiers
urn:nbn:se:lnu:diva-25987 (URN)000327180500266 ()978-4-88552-277-2 (ISBN)
Conference
International Symposium on Electromagnetic Theory (EMTS), May 20-23, 2013, Hiroshima
Available from: 2013-05-31 Created: 2013-05-31 Last updated: 2017-01-11Bibliographically approved
Gustafsson, S., Nordebo, S. & Nilsson, B. (2012). An electromagnetic dispersion model for HVDC Power Cables. In: : . Paper presented at The 6th International Conference on Inverse Problems: Modeling and Simulation, Antalya, Turkey, May 21-26, 2012 (pp. 214-215).
Open this publication in new window or tab >>An electromagnetic dispersion model for HVDC Power Cables
2012 (English)Conference paper, Published paper (Refereed)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:lnu:diva-19212 (URN)
Conference
The 6th International Conference on Inverse Problems: Modeling and Simulation, Antalya, Turkey, May 21-26, 2012
Available from: 2012-05-31 Created: 2012-05-31 Last updated: 2017-01-10Bibliographically approved
Gustafsson, S. (2012). Electromagnetic dispersion modeling and analysis for HVDC power cables. (Licentiate dissertation). Växjö
Open this publication in new window or tab >>Electromagnetic dispersion modeling and analysis for HVDC power cables
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Derivation of an electromagnetic model, regarding the wave propagation in a very long (10 km or more) High Voltage Direct Current (HVDC) power cable, is the central part of this thesis. With an existing “perfect” electromagnetic model there are potentially a wide range of applications.The electromagnetic model is focused on frequencies between 0 and 100 kHz since higher frequencies essentially will be attenuated. An exact dispersion relation is formulated and the propagation constant is computed numerically. The dominating mode is the first Transversal Magnetic (TM) mode of order zero, denoted TM01, which is also referred to as the quasi-TEM mode. A comparison is made with the second propagating TM mode of order zero denoted TM02. The electromagnetic model is verified against real time data from Time Domain Reflection (TDR) measurements on a HVDC power cable. A mismatch calibration procedure is performed due to matching difficulties between the TDR measurement equipment and the power cable regarding the single-mode transmission line model.An example of power cable length measurements is addressed, which reveals that with a “perfect” model the length of an 80 km long power cable could be estimated to an accuracy of a few centimeters. With the present model the accuracy can be estimated to approximately 100 m.In order to understand the low-frequency wave propagation characteristics, an exact asymptotic analysis is performed. It is shown that the behavior of the propagation constant is governed by a square root of the complex frequency in the lowfrequency domain. This thesis also focuses on an analysis regarding the sensitivity of the propagation constant with respect to some of the electric parameters in the model. Variables of interest when performing the parameter sensitivity study are the real relative permittivityand the conductivity.

Place, publisher, year, edition, pages
Växjö: , 2012. p. 10
Keyword
HVDC power cables, electromagnetic model, TDR measurement, sensitivity analysis, dispersion relation, propagation constant, low-frequency asymptotics
National Category
Other Physics Topics
Identifiers
urn:nbn:se:lnu:diva-32525 (URN)
Presentation
2012-12-11, D1136, Växjö, 13:15 (English)
Opponent
Supervisors
Available from: 2014-08-19 Created: 2014-02-27 Last updated: 2014-08-19Bibliographically approved
Gustafsson, S., Nordebo, S. & Nilsson, B. (2012). Electromagnetic dispersion modeling and sensitivity analysis for HVDC power cables. Växjö: Linnaeus University, Scool of Computer Science, Physics and Mathematics
Open this publication in new window or tab >>Electromagnetic dispersion modeling and sensitivity analysis for HVDC power cables
2012 (English)Report (Other academic)
Abstract [en]

This paper addresses electromagnetic wave propagation in High Voltage Direct Current (HVDC) power cables. An electromagnetic model, based on long (10 km or more) cables with a frequency range of 0 to 100 kHz, is derived. Relating the frequency to the propagation constant a dispersion relation is formulated using a recursive approach. The propagation constant is found numerically with normalized residue calculation. The paper is concluded with a sensitivity analysis of the propagation constant with respect to the electrical parameters εr (the real relative permittivity) and σ (the conductivity)

Place, publisher, year, edition, pages
Växjö: Linnaeus University, Scool of Computer Science, Physics and Mathematics, 2012
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:lnu:diva-22296 (URN)
Available from: 2012-11-14 Created: 2012-11-06 Last updated: 2017-01-10Bibliographically approved
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