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Methodologies for the charge estimation in the leader corona region used in modeling long air gaps underpositive voltage impulses
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Lightning Research Group)ORCID iD: 0000-0002-3094-4120
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Lightning Research Group)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. HVDC ABB AB. (Lightning Research Group)
2016 (English)Conference paper (Refereed)
Abstract [en]

Different methodologies have been proposed to represent the physical phenomena taking place in a laboratory electrical breakdown event. The implementation of these methodologies in numerical routines is based in several physical assumptions and a proper calculation of the electrostatic potential distribution. The whole electrical breakdown in air tested with switching-like voltage impulses can be subdivided into three main stages: first, the streamer inception (first corona), then the streamer to leader transition (second corona, leader inception) and the leader propagation. An important element in the last stage is the representation of the leader corona region (streamer region) in front of the leader tip channel as it propagates towards ground. In this paper, with the aid of a finite element method solver to determine the electric potential distribution, two new methodologies to quantify the amount of charge produced in the leader corona region were presented and compared with other ones available in the literature.

Place, publisher, year, edition, pages
2016.
Keyword [en]
high voltage testing, leader type discharge, leader corona region
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-297880OAI: oai:DiVA.org:uu-297880DiVA: diva2:943947
Conference
33rd International Conference on Lightning Protection 2016
Available from: 2016-06-28 Created: 2016-06-28 Last updated: 2016-09-05
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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