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Numerical modeling of long air gaps tested with positive switching impulses
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences. (Lightning Research Group)ORCID iD: 0000-0002-3094-4120
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. HVDC ABB AB. (Lightning Research Group)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Lightning Research Group)
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The numerical modeling of electrical gas discharges occurring in atmospheric air have been in continuous development during the last decades in different fields like high voltage techniques and lightning protection. Different methodologies have been proposed to represent the different physical phenomena taking place at a single full discharge event, departing both from experimental and theoretical approaches. The implementation of these methodologies in numerical routines combined with the use of a finite element method solver to determine the electric potential distribution, permits creation of models whose predictions closely agree with the real situations, where electrode arrangements might include non-symmetric geometries. In this paper, we present the results obtained using a new version of a simulation methodology that have been evolving during the last years, including new elements like the three-dimensional leader tortuosity from experimental measurements and two new methods for the leader-corona charge estimation. Results from the simulation were compared with experimental records and a good agreement is found between them.

Keyword [en]
Gas discharge, electric breakdown, EHV insulation, UHV insulation
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Atmospheric Discharges
Identifiers
URN: urn:nbn:se:uu:diva-298356OAI: oai:DiVA.org:uu-298356DiVA: diva2:945859
Available from: 2016-07-04 Created: 2016-07-04 Last updated: 2016-09-05Bibliographically approved
In thesis
1. Numerical modelling of positive electrical discharges in long air gaps
Open this publication in new window or tab >>Numerical modelling of positive electrical discharges in long air gaps
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This dissertation deals with research on the numerical modelling of electrical discharges in laboratory long air gaps excited with positive switching impulses. It begins with the preliminary work of several scientists during the last decades, making a detailed analysis of different approaches for modelling all the stages in a full discharge. The relations between these models are identified as well as the effect on the outcome when modifying some important input parameters.

The general concept describing the discharge phenomenon usually includes three main elements: the streamer inception, the streamer-to-leader transition and the stable leader propagation. These elements are present in many of the analysed models and the main differences between them are the assumptions and simplifications made by each author at a specific point in their methodologies. The models are usually simplified by assigning experimentally determined values to physical constants pertinent to different stages of the full discharge. These constants are the potential gradient in the leader-corona region to sustain the leader propagation, the charge per unit length along the leader channel which depends on the atmospheric conditions and the voltage impulse wave shape; and the leader propagation velocity, which is closely related to the discharge current. The dissertation includes the results of laboratory work related the study of leaders in long gap discharges, electrical parameters and optical records. By reconstructing the three-dimensional leader propagation for the rod-to-plane configuration, it was possible to study the random tortuous path followed by the leader as it propagates.

One important element included in the discharge modelling is the representation of the leader-corona region in front of the leader tip as it propagates towards the grounded electrode. For the calculation of the net charge available in the leader-corona region, two new methodologies were pro-posed based on the electrostatic potential distribution obtained from a finite element method solver. This allowed the inclusion of more elements representing different parts of the discharge in the simulation domain.

In the final part, all the analysed elements and the new proposed ones were included in a new methodology for the modelling of electrical dis-charges in long air laboratory gaps. The results obtained from this methodology were compared to experimental data. A good agreement was found between the simulation results and the experimental data.

Place, publisher, year, edition, pages
Uppsala, Sweden: Acta Universitatis Upsaliensis, 2016. 58 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1389
Keyword
high voltage techniques, numerical modeling, electrical discharge in gases, streamer mechanism, leader channel
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Atmospheric Discharges
Identifiers
urn:nbn:se:uu:diva-298355 (URN)978-91-554-9623-4 (ISBN)
External cooperation:
Public defence
2016-09-15, Polhemsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2016-08-25 Created: 2016-07-04 Last updated: 2016-09-05

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