| 1. |
- Abrahamsson, Lars, et al.
(författare)
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An electromechanical moving load fixed node position and fixed node number railway power supply systems optimization model
- 2013
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Ingår i: Transportation Research Part C. - : Elsevier BV. - 0968-090X .- 1879-2359. ; 30, s. 23-40
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents an optimization model for simulations of railway power supply systems. It includes detailed power systems modeling, train movements in discretized time considering running resistance and other mechanical constraints, and the voltage-drop-induced reduction of possible train tractive forces. The model has a fixed number of stationary power system nodes, which alleviates optimized operation overtime. The proposed model uses SOS2 (Special Ordered Sets of type 2) variables to distribute the train loads to the two most adjacent power system nodes available. The impacts of the number of power system nodes along the contact line and the discretized time step length on model accuracy and computation times are investigated. The program is implemented in GAMS. Experiences from various solver choices are also discussed. The train traveling times are minimized in the example. Other studies could e.g. consider energy consumption minimization. The numerical example is representative for a Swedish decentralized, rotary-converter fed railway power supply system. The proposed concept is however generalizable and could be applied for all kinds of moving load power system studies.
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| 2. |
- Abrahamsson, Lars, et al.
(författare)
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Modern methods for balancing of single phase loads when feeding a.c. Electrified railways
- 2017
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Ingår i: Eb - Elektrische Bahnen. - : Vulkan Verlag. - 0013-5437. ; 115, s. 13-19
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Tidskriftsartikel (refereegranskat)abstract
- Conventional compensation circuits for phase balancing of single phase AC railways for 50 or 60 Hz have high cost for the associated transformers. A new version of the classical Steinmetz scheme, using three single phase transformers connected as a W with the phase angles -60°, 0° and +60°, can reuse the two standard single phase transformers of a V-connected feeding station with a third identical transformer added. Power factor compensation can easily be included. For neutral sections between different feeding systems, a neutral section converter is proposed.
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| 3. |
- Abrahamsson, Lars, et al.
(författare)
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Use of converters for feeding of AC railways for all frequencies
- 2012
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Ingår i: Energy for Sustainable Development. - : Elsevier. - 0973-0826 .- 2352-4669. ; 16:3, s. 368-378
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Tidskriftsartikel (refereegranskat)abstract
- Railways are the most energy-efficient land-based mode of transport, and electrification is the most energy-efficient way to power the trains. There are many existing solutions to supply the trains with electricity. Regardless of which particular technology is chosen, it is beneficial to interconnect the public power grids to grids supplying power to the railways. This paper shows that the most efficient, flexible, and gentle-for-the-public-grid way of doing that is through power electronic-based power converters. Converters offer great benefits regardless of whether the overhead contact lines are of DC-type or AC type, and regardless of the AC grid frequency. This paper presents neither new theory nor new experimental results. Based on already available information, this paper presents logical arguments leading to this conclusion from collected facts. Over time what used to be advanced and high-cost equipment earlier can nowadays be purchased at reasonable cost. It is obvious that for most electrically-fed railways, the use of modern power converters is attractive. Where the individual trains are high consumers of energy, the railway gradients are substantial, and the public grids feeding the railway are weak, the use of converters would be technically desirable, if not necessary for electrification.It is expected that more high-speed railways will be built, and more existing railways will be electrified in the foreseeable future. This paper could provide some insights to infrastructure owners and decision makers in railway administrations about value additions that converter-fed electric railways would provide.
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| 4. |
- Laury, John
(författare)
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Transient Stability in Low Frequency Railways with Mixed Electronic and Rotational Generation
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Transient stability concerns the ability of a power system to maintain synchronism after a large disturbance. Transient stability plays an important role in guaranteeing operational security and reliability and has been extensively studies for large 50 Hz and 60 Hz transmission systems. However, transient stability of low frequency railway grids has not been properly investigated.As low frequency railway grids operate at another frequency than the public grid, conversion of frequency is needed. This conversion is performed by Rotary Frequency Converters or by Static Frequency Converters. These two types of converters have a different impact on stability. In this thesis, the overall aim is to obtain knowledge on transient stability in low frequency railway grids, with focus on the Swedish synchronous-synchronous railway grid with a mix of Rotary and Static Frequency Converters.The transient stability problem is approached by developing a simplified model of a Static Frequency Converter that can be used for the stability studies in low frequency railways. The Static Frequency Converter is modelled as single phase generator with an equivalent inertia and damping. However as Static Frequency converters cannot handle currents much above their ratings, current limitation is implemented. The current limitation is needed to avoid unnecessary tripping of the converter during fault or other high current situations. With the model developed for a Static Frequency Converter and with a simplified model of a Rotary Frequency Converter, transient stability studies have been performed for several test systems representing the Swedish railway grid.The simulations performed shows the appearance of power oscillations after a large disturbance, between a Static Frequency Converter and a Rotary Frequency Converter when these are operating in parallel. The simulations also showed that the systems studied were stable for realistic values of the fault-clearing time.
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| 5. |
- Lindeberg, Per-Anders, et al.
(författare)
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Blitzeinwirkungen auf Oberleitungs- und Signalanlagen in Schweden
- 2007
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Ingår i: Elektrische Bahnen. ; :1-2, s. 67-80
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
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| 7. |
- Midya, Surajit, et al.
(författare)
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Conducted and Radiated Emission from Pantograph Arcing in AC Traction System
- 2009
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Ingår i: General Meeting of the IEEE-Power-and-Energy-Society Calgary, CANADA, JUL 26-30, 2009. - New York : IEEE. - 9781424442409 ; , s. 2700-2707
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Konferensbidrag (refereegranskat)abstract
- One of the most common and yet unavoidable problems in electrified railways are because of pantograph arcing. The intensity of arcing increases during winter because of the ice layer on the overhead contact wire. In AC traction system, pantograph arcing distorts the sinusoidal waveforms of the supply voltage and current. It also generates transients at the current zero crossings (CZC). All these result in a net DC component, harmonics and radiated emission. In this paper we will present an experimental investigation to understand pantograph arcing and influence of power factor on conducted and radiated emission. We found that pantograph arcing generates both conducted and radiated emission in a wide band, starting from DC. Both the DC component and higher order conducted and radiated emission increases with line speed. Running the train at lower power factor can reduce the DC component and emerging as the most preferred solution against problems due to ice in cold weather.
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| 8. |
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| 9. |
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| 10. |
- Midya, Surajit, et al.
(författare)
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DC Component From Pantograph Arcing in AC Traction System : Influencing Parameters, Impact, and Mitigation Techniques
- 2011
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Ingår i: IEEE transactions on electromagnetic compatibility (Print). - : IEEE conference proceedings. - 0018-9375 .- 1558-187X. ; 53:1, s. 18-27
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Tidskriftsartikel (refereegranskat)abstract
- Pantograph arcing in ac traction system generates transients, and causes asymmetries and distortion in supply voltage and current waveforms. These asymmetric voltage and current lead to a net dc component and harmonics that propagate within the traction power and signalling system and cause electromagnetic interference. This problem is enhanced during winter because of the layer of ice/snow on the overhead contact wire. The sliding contact becomes poor and a visible arc moves along with the pantograph. In this paper, it is shown how different parameters like traction current, line speed, power factor, and supply voltage influence the arcing, its characteristics, and the dc components. It is shown that the dc current component increases with increasing train speed and traction current, and reduces at a lower power factor. It is also discussed how the presence of an ice layer influences the arcing and the dc components. It is found that running the trains below the normal operating power factors is an effective choice to mitigate this problem. The findings presented in this paper could be beneficial to estimate the probable limit of the dc component at the planning stage so that proper precautions can be taken at the design stage itself.
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| 11. |
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| 12. |
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| 13. |
- Midya, Surajit, et al.
(författare)
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Pantograph Arcing in Electrified Railways-Mechanism and Influence of Various Parameters-Part II : With AC Traction Power Supply
- 2009
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Ingår i: IEEE Transactions on Power Delivery. - USA : IEEE. - 0885-8977 .- 1937-4208. ; 24:4, s. 1940-1950
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Tidskriftsartikel (refereegranskat)abstract
- Pantograph arcing with ac supply generates transients, cause asymmetries and distortion in supply voltage and current waveforms and can damage the pantograph and the overhead contact line. The asymmetry generates a net dc component and harmonics, which propagate within the traction power and signalling system and causes electromagnetic interference. Unlike dc-fed systems (Part I), the arcing in ac supply is complex because of the zero crossing of currents and voltages. In this paper, we discuss the mechanisms of sliding contact and arcing between pantograph-contact wire using the experimental setup described in Part I. Influences of various parameters and test conditions on arcing phenomenon and their signature patterns on the supply voltage and current waveforms are presented. It is shown how the arcing mechanism and corresponding asymmetry in the voltage and current waveforms are governed by line speed, current, supply voltage, inductive load, and pantograph material. The asymmetry in the current waveform is mainly due to the difference in the duration of successive zero-current regions and uneven distortion of the waveshapes. This, in turn, creates the asymmetry in the voltage waveform. The findings presented in this paper could be beneficial for coming up with appropriate mitigation techniques from the electromagnetic interference due to pantograph arcing in ac traction systems.
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| 14. |
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| 15. |
- Midya, Surajit, et al.
(författare)
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Understanding Pantograph Arcing in Electrified Railways - Influence of Various Parameters
- 2008
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Ingår i: IEEE International Symposium on Electromagnetic Compatibility Detroit, MI, AUG 18-22, 2008. - NEW YORK : IEEE. ; , s. 592-597
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Konferensbidrag (refereegranskat)abstract
- The most common and yet unavoidable EMC problems with electrified railways are due to pantograph arcing. This distorts the waveform of the supply voltage and current, can generates transients during the zero crossings of the current and can cause interference with the traction power and signalling system. Pantograph arcing is a complex phenomenon and depends on speed of the train, current, presence of inductance etc. In a sliding contact like pantograph and contact wire, the am root moves across both electrodes because of the relative motion between them. In this paper, we will present an experimental analyses of the are root movement and influence of different parameters on it using a laboratory setup.
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| 16. |
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| 17. |
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| 18. |
- Theethayi, Nelson, et al.
(författare)
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Lightning interaction with the swedish railway network
- 2007
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Konferensbidrag (refereegranskat)abstract
- 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.
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