Stochastic effects and uncertainties in assessing electromagnetic interactions with control systems [Elektronische Ressource] / von Velislav Varbanov

Vvarbanov

Informations

• Publié par: otto-von-guericke-universitat_magdeburg
• Publié le: 01 janvier 2005
• Nombre de lectures: 29
• Langue: English
• Poids de l'ouvrage: 8 Mo

Extrait

Stochastic effects and uncertainties in assessing
electromagnetic interactions with control systems



Dissertation
zur Erlangung des akademischen Grades



Doktoringenieur
(Dr.-Ing.)



von Dipl.-Ing. Velislav Varbanov
geb. am 07.01.1972 in Burgas


genehmigt durch die Fakultät für Verfahrens- und Systemtechnik
der Otto-von-Guericke-Universität Magdeburg


Gutachter: Prof. Dr.-Ing. habil. Ulrich Hauptmanns
Prof. Dr.-Ing. Günter Wollenberg
Dr.-Ing. Ralf-Michael Zander

Promotionskolloquium am 09.06.2005

Abstract


Nowadays the control system units operate at very low threshold energy levels. It is very
important that such devices are not susceptible to emissions (either conducted or radiated)
produced by other systems, or by the electromagnetic fields of natural sources, such as,
lightning. The most frequent mechanism of electromagnetic interference caused by lightning
on electronic components is the interaction of the discharge with the transmission line to
whose end the device is connected. In order to protect the system against such events, an
investigation of the voltage surges at the end of the line caused by this external field is
necessary. The present work evaluates the voltage surges at the end of an underground-
located low-voltage transmission line in the case of nearby lightning. The knowledge of the
extent of the surges will allow appropriate decisions for the protection of the devices at the
end of the line to be taken. Very important in this investigation is to take into account the
stochastic nature of the input parameters. It manifests itself by differences in distance between
the wires in the conductors, variation of the conductor and insulation diameters and different
properties of the insulation and surrounding medium, along the length of the line. In many
cases this stochastic nature is neglected, but it can be responsible for variations of the results
up to several orders of magnitude.
Kurzreferat


Kontrollsysteme von heute arbeiten mit sehr niedriger Energie. Es ist wichtig, dass solche
Systeme nicht beeinflusst werden durch die elektromagnetischen Emissionen anderer Geräte
oder durch die von einer natürlichen Quelle hervorgerufenen elektromagnetischen Felder wie
z.B. Blitzeinschläge. Die häufigste Ursache einer elektromagnetischen Störung verursacht
durch einen Blitzeinschlag auf elektronischen Komponenten ist der Einfluß der
Blitzentladung auf das Endgerät durch Übertragung in der elektrischen Leitung. Um die
Systeme vor solchen Einwirkungen zu schützen, müssen Untersuchungen bezüglich des
Spannungsverhaltens am Ende der elektrischen Leitung gemacht werden. Diese Arbeit
beschäftigt sich mit dem Spannungsverhalten am Ende der Leitung von unter der Erde
befindlichen elektrischen Leitungen mit einer niedrigen Spannung bei einem unmittelbaren
Blitzeinschlag. Das Wissen über die Größe des Störungssignals würde uns die Einrichtung
passender Schutzmassnahmen für solche Ereignisse ermöglichen. Sehr wichtig für die
Untersuchung ist es, die stochastische Natur von Eingangsparametern zu berücksichtigen. Die
stochastische Natur berücksichtigt die realen Bedingungen von Leitungen unter der Erde
ebenso wie die Beschaffenheit der Umgebung. In den meisten Berechnungen wird dies
vernachlässigt, obwohl der Einfluss auf das Ergebnis mehren Größenordnungen ausmachen
kann.








Contents
1. Introduction .................................................................................................................................... 1
1.1 Motivation...................................................................................................................... 2
1.2 Approach and outline ..................................................................................................... 3
2. Electromagnetic interference.......................................................................................................... 5
2.1 Sources of natural disturbance ....................................................................................... 6
2.1.1 The magnetic field of the earth and geomagnetic storms................................... 6
2.1.2 Atmospheric noise..............................................................................................9
2.2 Disturbances due to human activities........................................................................... 11
2.2.1 Disturbances caused by radio-frequency transmitters...................................... 12
2.2.1.1 Radio and television broadcasting transmitters........................................................... 13
2.2.1.2 Radars..........................................................................................................................14
2.2.2 Unintentional sources of radiation ................................................................... 14
2.2.2.1 Industrial, scientific and medical (ISM) equipment.................................................... 15
2.2.2.2 Electronic data-processing (EDP) equipment ............................................................. 15
2.2.2.3 Ignition systems for internal combustion engines of vehicles..................................... 16
2.3 Electromagnetic compatibility - standards 16
3. Lightning discharge as a major source of interference......................................................... 25
3.1 The discharge process of negative cloud-to-ground lightning 25
3.2 The return strokes......................................................................................................... 30
3.2.1 Lightning current at the base of the channel .................................................... 31
3.2.2 Mathematical modeling of the subsequent return stroke current
waveform.......................................................................................................... 33
3.2.3 Electromagnetic field produced by the lightning discharge............................. 37
3.2.4 Mathematical model of the electromagnetic field radiated by the
subsequent return stroke................................................................................... 39
3.2.5 Simulation models for the return stroke........................................................... 45
3.2.6 “Engineering” models for the simulation of the return stroke process ............ 46
3.2.7 “LEMFieldE” – a program for simulation of the consequences of a
lightning stroke................................................................................................. 50
3.2.8 Comparison of the results calculated by “LEMFieldE” with those
stated in the literature ....................................................................................... 58
3.3 The stochastic nature of lightning ................................................................................ 68
4. Case study – investigation of lightning flash interaction with a transmission line as
part of the control system ..................................................................................................... 73
4.1 Description of the line.................................................................................................. 73
4.2 Electrical dimensions of a transmission line................................................................ 77
4.3 Deterministic study of the interaction of lightning with the line ................................. 80
I4.3.1 Distant strike and electromagnetic field coupling............................................ 81
4.3.2 Direct lightning strike and crosstalk between the conductors.......................... 85
4.3.3 Results of the deterministic approach .............................................................. 92
4.4 Stochastic simulation of a direct strike over the line ................................................... 94
4.4.1 Pdf distribution of the input stochastic parameters .......................................... 95
4.4.2 Development and comparison between the 22-point model and the
204-point model ............................................................................................... 97
4.4.2.1 Partial stochastic simulation showing the influence of individual parameters.......... 103
4.4.2.2 Stochastic simulation with all parameters................................................................. 107
4.4.2.3 Evaluation of the stochastic results ........................................................................... 112
4.5 Determination of the expected lightning frequency as an initiating event................. 120
5. Summary and outlook ........................................................................................................ 128
Bibliography ………………………………………...…………………….……………….………... 130
Appendix I ….……………………………………………………………………………………….. 139
Appendix II ………………………………… 158
Appendix III …..…………………………………………………………………………………….. 167



IITable of utilized symbols and abbreviations

Latin Symbols

Unit
Symbol Unit Description
Symbol
Identity matrix 1 n - -