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Multi-conductor transmission line model for electrified railways: A method for including responses of lumped devices
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

For studying the response to transients caused by lightning and other electromagnetic disturbance sources, electrified railway systems can be represented as a system of multiconductor transmission lines (MTL) above a finitely conducting ground. The conductors present in this system would be wires for traction power supply, auxiliary power, return conductors for traction current, the tracks, and finitely conducting ground. In contrast to conventional power systems, where the MTL system is usually only terminated at the line ends, there are lumped devices connected in series and as shunt along the railway network, for example, booster and auto transformers, track circuits, and various interconnections between conductors, influencing surge propagation. In this doctorial thesis a new method for incorporating lumped series and shunt connected devices along MTL systems is presented. Telegrapher’s equations, using the finite difference time domain method, are adopted for finding surge pulse propagations along the MTL systems, simultaneously solving for the lumped devices connected along the lines by means of Kirchoff’s laws for nodal currents and voltages using a circuit solver.

As part of this work, case studies are carried out to determine voltages appearing across devices connected along MTL systems representative of a typical Swedish single-track electrified railway system, in cases of direct and indirect lightning strikes. The influence of soil ionization at the grounding points and the nonlinear phenomenon of flashovers between overhead wires and the poles are also investigated. The calculations made show that the devices connected along this system, which are needed for normal and safe operation of the railway system, and nonlinearities are affecting the surge current and voltage distribution and peaks appearing along the MTL system and across devices.

Place, publisher, year, edition, pages
Stockholm: KTH , 2010. , x, 80 p.
Series
Trita-EE, ISSN 1653-5146 ; 2010:006
Identifiers
URN: urn:nbn:se:kth:diva-11964ISBN: 978-91-7415-557-0 (print)OAI: oai:DiVA.org:kth-11964DiVA: diva2:291290
Public defence
2010-02-24, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2010-02-01 Created: 2010-02-01 Last updated: 2012-03-26
List of papers
1. Lightning interaction with the swedish railway network
Open this publication in new window or tab >>Lightning interaction with the swedish railway network
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2007 (English)Conference paper, Published paper (Refereed)
Abstract [en]

In the beginning, the design of signal and control network of railways in early times was not always done in accordance with the strict rules of Electromagnetic Compatibility (EMC). This created problems due to Electromagnetic Interference (EMI) when old electro-mechanical signalling, control and communication systems were replaced by modern sensitive electronic circuits. Modern developments in the railway systems have made the system more vulnerable to lightning transients, a natural source of EMI, because the overall network is not designed to reduce the lightning surges to the low levels tolerable to the electronic systems widely being introduced in the railway system. Railway networks are extensive and modernization of signal/control/communication systems is carried out only in stages at different times, it is not unusual to find transient related problems in a section of the network on account of inadequate lightning protection design or EMC design of the existing network in which a new module (equipment or system) is introduced.  One wonders if these problems act as a brake on the upgrading plans of the railways. Also the new railway systems which incorporate advanced signal/control/communication systems sometimes suffers from the effects of lightning transients because many of the standards and guidelines used in the design dates back to the age of electromechanical devices and hence do not include robust transient protection design. There were many attempts to address EMC issues in railways, but usually these attempts were confined to solving immediate problems of EMI due to introduction of new locomotive drives and EMI due to sparks at the pantograph. A comprehensive review of railway system from the angle of lightning protection and EMC is not yet carried out.  This work discusses the EMC problems of large distributed systems, with particular reference to lightning interaction with Swedish rail network.

Keyword
Transmission line, lightning attachment, crosstalk, transients.
Identifiers
urn:nbn:se:kth:diva-11931 (URN)
Conference
Railway Engineering
Note
Presented at the Railway Engineering Conference 2007 LondonAvailable from: 2010-02-04 Created: 2010-01-27 Last updated: 2010-04-28
2. Blitzeinwirkungen auf Oberleitungs- und Signalanlagen in Schweden
Open this publication in new window or tab >>Blitzeinwirkungen auf Oberleitungs- und Signalanlagen in Schweden
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2007 (German)In: Elektrische Bahnen, no 1-2, 67-80 p.Article in journal (Refereed) Published
Abstract [de]

Für ältere elektrotechnische Bahnanlagen waren die Aspekte der elektromagnetischen Verträglichkeit von geringerer Bedeutung als für heutige Anlagen. Vor allem für neuere Signal- und Zugerkennungsanlagen mit kleineren Abmessungen sanken die erlaubten Höchstwerte für Ströme und Spannungen. Dies hat die Störungsempfindlichkeit erhöht. Eine wichtige, wenn nicht die wichtigste Störungsquelle sind atmosphärische Entladungen, also Blitze. Ihre Einwirkung auf elektrifizierte Bahnstrecken in Schweden wurde theoretisch durch Simulationen untersucht. Die Empfindlichkeit der Komponenten wurde experimentell geprüft. Bei Bahnanlagen reicht die Ableitung von Blitzen nicht aus, um Schäden durch Blitzentladungen zu vermeiden. Gefährdete Komponenten sollten durch angemessene Maßnahmen gegenüber elektromagnetischen Störungen besser geschützt werden.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-11932 (URN)
Note

QCR 20161209

Available from: 2010-02-04 Created: 2010-01-27 Last updated: 2016-12-09Bibliographically approved
3. Review of Research on Lightning Interaction with the Swedish Railway Network
Open this publication in new window or tab >>Review of Research on Lightning Interaction with the Swedish Railway Network
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2008 (English)Conference paper, Published paper (Refereed)
Abstract [en]

In the early electrified railway systems, the design of signal and control networks were not always made in accordance with the strict rules of Electromagnetic Compatibility (EMC). This created problems due to Electromagnetic Interference (EMI) when old electro-mechanical signalling, control and communication systems were replaced by modern sensitive electronic circuits. Modern developments in the railway systems have made the system more vulnerable to lightning transients, a natural source of EMI, because the overall network is not designed to reduce the lightning surges to the low levels tolerable to the electronic systems widely being introduced in the railway system. Railway networks are extensive and modernization of signal/control/communication systems are carried out in stages at different times, it is not unusual to find transient related problems in a section of the network on account of inadequate lightning protection design or EMC design of the existing network in which a new module (equipment or system) is introduced. These problems may act as a brake on the upgrading plans of the railways. Also the new railway systems which incorporate advanced signal/control/communication systems sometimes suffers from the effects of lightning transients because many of the standards and guidelines used in the design dates back to the age of electromechanical devices and hence do not include robust transient protection design. There have been many attempts to address EMC issues in railways, but usually these attempts were confined to solving immediate problems of EMI due to introduction of new locomotive drives and EMI due to sparks at the pantograph. A comprehensive review of railway system from the angle of lightning protection and EMC is not yet fully carried out.

The Swedish National Rail Administration (Banverket) reported a delay of about 900-1000 hours in the years 2001-02. Lightning transients were found to damage important devices that control train movements, causing traffic stoppage and delays. This work therefore discusses the EMC problems of large distributed systems, with particular reference to lightning interaction with Swedish rail networks [1]. Lightning induces transient overvoltages in railway conductor systems such as tracks, overhead wires, and underground cables, either due to direct lightning strike to the system or due to the coupling of electromagnetic fields from remote strikes. Models based on multiconductor transmission line theory were developed for calculating the induced voltages and currents [1-3]. Some experiments have also been carried out to better understand the way in which the lighting transients’ couple into the systems and also to verify the models used for analysis [4]. From experiments high frequency behavior of different types of transformers used within the railway systems were also derived [1, 6].  Besides, experimental studies on lightning induced transients entering railway systems, failure modes of relay and rectifier units used in the train position/signaling applications for lightning transients are performed. The simulation models are being converted to user friendly software for the practicing engineers of the railway industry [1].

Identifiers
urn:nbn:se:kth:diva-11935 (URN)
Note
Presented at the EuroEM Conference 2008, Lausanne, SwitzerlandAvailable from: 2010-02-04 Created: 2010-01-27 Last updated: 2010-04-28
4. Modeling of Passive Series Devices on Multiconductor Transmission Lines for Transient Analysis in Power and Railway Systems
Open this publication in new window or tab >>Modeling of Passive Series Devices on Multiconductor Transmission Lines for Transient Analysis in Power and Railway Systems
2008 (English)In: EuroEM Conference 2008, 2008Conference paper, Published paper (Refereed)
Abstract [en]

Usually the crosstalk or field to wire coupling mechanisms in multiconductor transmission lines (MTL) are studied considering lumped loads or devices connected at the line terminations (at source and load ends) or as shunt load to ground along the lines, as seen in conventional power system networks e.g. [1-3]. However there are practical systems, e.g. in typical Swedish railway systems, wherein discrete devices exist in series with the line (booster transformers) or in shunt between the lines (auto transformers and track circuits). With lightning transients various parameters that influence crosstalk in MTL systems, such as the ground conductivity, have been analyzed e.g. in [1].

We shall present various cases of crosstalk mechanisms when the devices are connected either in series with the line or in shunt between the lines. The method used for simulating the voltage and current pulse propagation along the MTL systems is the FDTD method [4] in conjunction with the recursive convolution proposed in [5] for inclusion of ground losses. The passive series components connected along the MTL are simulated by the circuit solver ATP/EMTP [6, 7]. Emphasis will be given to present the model that connects the FDTD routine with the circuit solver in a more efficient way. The currents entering or leaving a given type of component at a given position along the lines are modeled as time dependant current sources in the circuit solver and the terminal voltages appearing in the circuit are returned to the FDTD routine as node voltages.

We shall also present the efficacy of the proposed method and mathematically discuss the validity of the present work. The influence of finitely conducting ground on the current pulse propagation is also included in the analysis. From the crosstalk analysis it is also shown that the series connected passive devices cannot be disregarded as they largely influence pulses propagating on the lines in the event of transient phenomena due to lightning or switching. This study could be beneficial for future practical studies of surge protection and insulation coordination.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-11936 (URN)
Conference
European electromagnetics (EUROEM), 2008. Lausanne. July 21-25 2008
Note
QC 20111117Available from: 2010-02-01 Created: 2010-01-27 Last updated: 2011-11-17Bibliographically approved
5. A Method for Interfacing Lumped-Circuit Models and Transmission-Line System Models With Application to Railways
Open this publication in new window or tab >>A Method for Interfacing Lumped-Circuit Models and Transmission-Line System Models With Application to Railways
2009 (English)In: IEEE transactions on electromagnetic compatibility (Print), ISSN 0018-9375, E-ISSN 1558-187X, Vol. 51, no 3, 833-841 p.Article in journal (Refereed) Published
Abstract [en]

Transient analysis of lossy multiconductor transmission lines (MTL) have been studied using the finite difference time domain (FDTD) method with lumped loads/devices connected at line terminations. In electrified railway networks series and shunt devices (whose circuit models derived either from experiments/borrowed off the shelf), e.g., transformers, converters, switchgear, signal equipments, etc., are found distributed along the MTL system. To simulate such railway systems involving both transmission lines (TL) and lumped circuits, an interface technique between TL system solved using FDTD and all the lumped circuits solved using ATP/EMTP software (circuit solver) is proposed. This sufficiently accurate method is simple to apply as only instantaneous voltages and currents are transmitted between standalone FDTD routine and circuit solver. Moreover, the user avoids coding complex circuit models within the FDTD, while at the same time efficiently uses the potential of accurate frequency dependant loss models (nonexistent in circuit software) coded in FDTD. The technique is applied on typical electrified railway systems to demonstrate how traction transformers, track circuits, and line interconnections affect the propagating voltages and currents. The method could be beneficial for transient protection and insulation coordination studies in electrified railway systems.

Keyword
circuit simulation, crosstalk, power system simulation, transmission line modeling
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-11937 (URN)10.1109/TEMC.2009.2023112 (DOI)000269154400031 ()2-s2.0-69549129397 (Scopus ID)
Note
QC 20111004Available from: 2010-02-01 Created: 2010-01-27 Last updated: 2017-12-12Bibliographically approved
6. Influence of Discrete Series Devices on Crosstalk Phenomena in Multiconductor Transmission Lines
Open this publication in new window or tab >>Influence of Discrete Series Devices on Crosstalk Phenomena in Multiconductor Transmission Lines
2007 (English)In: EMC ZURICH-MUNICH 2007, SYMPOSIUM DIGEST, 2007, 245-248 p.Conference paper, Published paper (Refereed)
Abstract [en]

Usually the crosstalk mechanisms in multiconductor transmission lines (MTL) are studied considering lumped loads or devices connected at the line terminations (either at source or load ends) or as shunt load to ground along the lines, as seen in conventional power and railway system networks. However there are practical systems, e.g. like in typical Swedish railway systems, wherein discrete lumped devices like the booster transformer (BT) exist in series with the line. With lightning transients various parameters that influence crosstalk in MTL systems, such as the ground conductivity, have been analyzed e.g. in [1]. For realistic crosstalk analysis we conclude that inclusion of discrete devices like BT should be accounted. The study could be beneficial in better understanding of the crosstalk mechanism in the electrified railway systems.

National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-11938 (URN)10.1109/EMCZUR.2007.4388241 (DOI)000253707800061 ()
Conference
18th International Zurich Symposium on Electromagnetic Compatibility Location: Lab Electromagnet Field & Microwave Elect. Munich, GERMANY. SEP 24-28, 2007
Note
QC 20111117Available from: 2010-02-01 Created: 2010-01-27 Last updated: 2011-11-17Bibliographically approved
7. Method to Include Lumped Devices in Multi-conductor Transmission Line System Models
Open this publication in new window or tab >>Method to Include Lumped Devices in Multi-conductor Transmission Line System Models
2009 (English)In: 2009 IEEE POWER & ENERGY SOCIETY GENERAL MEETING, VOLS 1-8, 2009Conference paper, Published paper (Refereed)
Abstract [en]

Transient analysis and crosstalk in multiconductor transmission line (MTL) systems with internal and external losses has been widely studied by solving telegrapher’s equation using the finite difference time domain (FDTD) method. Most of those studies are carried out with lumped loads/devices connected at the line terminations (at source and load ends). However, in practical systems such as typical railway and power systems, lumped devices, like, transformers, rotary converter stations, line interconnections and insulators, substation and switchgear equipments (grounding systems, insulators, surge protectors, circuit breakers, etc.) and signaling equipments exist either in series or in shunt with the MTL systems, but not necessarily at the ends. Detailed/complex circuit models (linear or nonlinear) for all those devices either exist in the literature or can be developed from experiments. In this paper a more general method based on Kirchoff’s current law (nodal analysis) is proposed to interface the FDTD code with Alternative Transients Program/Electromagnetic Transients Program (ATP/EMTP) circuit simulation software for transient analysis with any complex circuit model along the MTL system. The method is efficient and simple and it could be beneficial for accurate and realistic transient protection, mitigation and insulation coordination studies in large distributed electrical systems. A case study is made for an electrified railway with booster transformer traction system.

Series
IEEE Power and Energy Society General Meeting-PESGM
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-11939 (URN)10.1109/PES.2009.5275252 (DOI)2-s2.0-71849095545 (Scopus ID)
Conference
General Meeting of the IEEE-Power-and-Energy-Society. Calgary, CANADA. JUL 26-30, 2009
Note
QC 20111117Available from: 2010-02-01 Created: 2010-01-27 Last updated: 2011-11-17Bibliographically approved

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