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Remote contact-free reconstruction of currents in two-dimensional parallel conductors
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH.ORCID iD: 0000-0002-9665-8557
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, the theory of the remote contact-free reconstruction of currents in two-dimensional parallel conductors is investigated. The motivation of this study is finding a complement technique to measurement transformers which are the well-established devices to measure currents in power transmission lines. This technique would provide the possibility of measuring currents at different locations of a power system, as well as, at different frequencies.

 

Remote contact-free determination of currents is an electromagnetic inverse source problem in which the currents are reconstructed from the magnetic field data collected by a set of sensors located in the vicinity of the conductors. Since the sensors are not too close to the conductors, the main challenge is the effect of the disturbance fields produced by the external sources in the measurement.

 

In the case that the external sources produce three-dimensional disturbance fields, the magnetic field due to the external sources is expressed as a truncated expansion of the spherical harmonics and both the currents in the conductors and the expansion coefficients are determined by applying the least square method. To overcome the ill-posedness of the problem, the functional to be minimized is augmented by a Tikhonov regularization term that penalizes unphysical solutions introduced by the expansion coefficients.

 

Finally, the problem of selecting a limited number of optimal sensor positions among a set of predetermined sensor positions is considered. Using the relaxation method, this optimization problem is changed to a convex optimization problem which can be readily solved using the CVX package.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. , p. 35
Series
TRITA-EE, ISSN 1653-5146 ; 2016:196
National Category
Engineering and Technology
Research subject
Electrical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-199635ISBN: 978-91-7729-240-1 (print)OAI: oai:DiVA.org:kth-199635DiVA, id: diva2:1064146
Presentation
2017-01-26, V3, Teknikringen 72, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20170116

Available from: 2017-01-16 Created: 2017-01-11 Last updated: 2017-01-16Bibliographically approved
List of papers
1. Current reconstruction from magnetic field using spherical harmonic expansion to reduce impact of disturbance fields
Open this publication in new window or tab >>Current reconstruction from magnetic field using spherical harmonic expansion to reduce impact of disturbance fields
2016 (English)In: Inverse Problems in Science and Engineering, ISSN 1741-5977, E-ISSN 1741-5985, p. 1-15Article in journal (Refereed) Published
Abstract [en]

A current reconstruction method, for determining currents in a set of parallel infinitely long conductors located above the ground from measured magnetic field, is developed. The method is designed to work even if three-dimensional external disturbance fields from external sources are present. The external field is written as an expansion in spherical harmonics. Therefore, the field in the different measurement points is regarded as a linear combination of the expansion coefficients and the currents to be determined. A linear equation system is formed with the currents and the expansion coefficients as the unknowns. The currents are reconstructed by solving the equation system using least squares method and Tikhonov regularization. If the characteristics of the ground below the conductors are known with sufficient precision, the ground effect can also be included into the model. Results of various simulations show that the method works well and noise in the measured magnetic field can be handled.

Place, publisher, year, edition, pages
Taylor & Francis Group, 2016
Keyword
Current reconstruction, inverse source problem, power line measurements, spherical harmonics, Tikhonov regularization, Ground effect, Inverse problems, Least squares approximations, Linear equations, Magnetic field measurement, Magnetic fields, Magnetism, Spheres, Power lines, Harmonic analysis
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-197209 (URN)10.1080/17415977.2016.1201661 (DOI)000399465600002 ()2-s2.0-84976254217 (Scopus ID)
Note

QC 20161212

Available from: 2016-12-12 Created: 2016-11-30 Last updated: 2017-06-02Bibliographically approved
2. Contact-free Measurement of Currents inTwo-dimensional Parallel Conductors Using the Green Identity Approach
Open this publication in new window or tab >>Contact-free Measurement of Currents inTwo-dimensional Parallel Conductors Using the Green Identity Approach
2016 (English)In: 2016 URSI International Symposium on Electromagnetic Theory, EMTS 2016, IEEE, 2016, p. 338-340, article id 7571391Conference paper, Published paper (Refereed)
Abstract [en]

The Green identity approach is used to reconstructcurrents in very long parallel conductors above the groundfrom magnetic field data measured at some points under theconductors. By assuming that the conductor positions are known,this method can be used for contact-free measurement of currentsin transmission lines in power system. This method gives thepossibility of measuring high-frequency currents which cannotbe measured with current transformers.

Place, publisher, year, edition, pages
IEEE, 2016
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-199633 (URN)10.1109/URSI-EMTS.2016.7571391 (DOI)000389770800097 ()2-s2.0-84992126325 (Scopus ID)978-1-5090-2502-2 (ISBN)
Conference
2016 URSI International Symposium on Electromagnetic Theory, EMTS 2016; Espoo; Finland; 14 August 2016 through 18 August 2016
Note

QC 20170116

Available from: 2017-01-11 Created: 2017-01-11 Last updated: 2017-03-07Bibliographically approved
3. Sensor Selection via Convex Optimization in Remote Contact-free Measurement of Currents
Open this publication in new window or tab >>Sensor Selection via Convex Optimization in Remote Contact-free Measurement of Currents
2017 (English)In: 2017 International Applied Computational Electromagnetics Society Symposium - Italy, ACES 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7916351Conference paper, Published paper (Refereed)
Abstract [en]

The sensor positions have substantial effect on the accuracy of remote contact-free reconstruction of currents in power transmission lines from magnetic field data, measured by a set of sensors located under the conductors. By maximizing a performance metric, based on the Fisher information matrix, Nopt sensors are selected from N candidate sensors. The main optimization problem is changed to a convex optimization problem using a relaxation of the integer constraints. The result for optimized sensor positions for a remote current reconstruction in power transmission lines using a planar sensor array is demonstrated.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2017
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-199687 (URN)10.23919/ROPACES.2017.7916351 (DOI)2-s2.0-85020042728 (Scopus ID)9780996007832 (ISBN)
Conference
2017 International Applied Computational Electromagnetics Society Symposium - Italy, ACES 2017, Firenze, Italy, 26 March 2017 through 30 March 2017
Note

QC 20170116

Available from: 2017-01-13 Created: 2017-01-13 Last updated: 2017-06-22Bibliographically approved

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