Electrified Railway Systems Research Articles

Modelling of a Double-Track Railway Contact System Electric Field Intensity

Working conditions of personnel that serves contact system (CS) are affected by factors including health and safety, security and working hours (danger of rolling stock accidents, danger of electric shock strokes, work at height, severity and tension of work, increased noise level, etc.) Low frequency electromagnetic fields as part of both electric and magnetic fields are among of the most dangerous and harmful factors. These factors can affect not only the working personnel, but also a lot of people, who do not work with the contact system itself, but could be influenced by electromagnetic field as the result of their professional activity. People, who use public transport or live not far from the electrified lines, are endangered by these factors as well. There are results of the theoretical researches in which low frequency electric fields of railway contact system were designed with the use of mathematical and computer modelling. Significant features of electric field distribution near double-track railway in presence or absence of human body were established. The studies showed the dependence of low frequency electric field parameters on the distance to the track axis, height, and presence or absence of human body. The obtained data were compared with permissible standards established in the Russian Federation and other countries with advanced electrified railway system. Evaluation of low frequency electric fields harmful effect on personnel is the main result of this work. It is also established, that location of personnel, voltage and current level, amount of tracks and other factors influence electric fields of contact systems.

Power Quality Conditioning in Railway Electrification: A Comparative Study

Electric transportation systems are a challenging load for three-phase transmission lines due to load variations, reactive power, imbalance, and harmonic pollution. Many power quality conditioners and compensation technologies have been developed to ensure compatibility with power systems. The most important ones are investigated, identifying parameters and performances for comparison, including evaluation of cost and size. A reference case is used for simulation, focusing on three-phase current intensity, current rate of rise, dc-link voltage, and dynamic response under various combinations of traction line load. The objective is to identify key characteristics supporting the selection of the appropriate compensation strategy for a new electrified railway system.

ANALYSIS OF ELECTROMAGNETIC INFLUENCE ON STEEL PIPELINES FROM THE ELEMENTS OF ELECTRIC POWER SYSTEM

A b s t r a c t: Power transmission lines often share same corridors with steel pipelines for oil and gas. When phase to ground fault occurs, high voltages may appear on the pipelines due to different mechanisms of mutual coupling. These voltages propagate at long distances from the fault location, and may pose a serious threat for the safety of the personnel and integrity of the pipeline. To provide adequate protection, calculation of the mutual coupling is required during the design stage of systems. Induced voltages are strongly influenced by the disposition of the both systems, their configuration and characteristics, elements that mutually interact etc. In this paper, we analyze induced voltages on practical pipeline system. Parametric analysis will show how far interventions on both systems can influence the induced voltages. Key words: electromagnetic influence; gas; oil; pipelines; safety REFERENCES: [1] Guide on the Influence of High Voltage AC Power Systems on Metallic Pipelines. Paris, CIGRE Working Group 36. 02, 1995. [2] Directives Concerning the Protection of Telecommunication Lines аgainst Harmful Effects from Electric Power and Electrified Railway Systems. Volume II: Calculating Induced Voltages and Currents in Practical Cases, Geneva, CCITT, 1989. [3] Guide for Assessment of Transferred EPR on Telecommunication Systems Due to Faults in A.C. Power Systems. Paris, CIGRE Working Group C4. 207, 2014. [4] Sunde. E. D.: Earth Conduction Effects in Transmission Systems. New York: Dover, 1968. [5] Wait, J. R.: Theory of Wave Propagation along a Thin Wire Parallel to an Interface. Radio Science. Vol. 7. pp. 675–679 (1972). [6] Directives Concerning the Protection of Telecommunication Lines against Harmful Effects from Electric Power and Electrified Railway Systems, Volume III, Capacitive, Inductive and Conductive Coupling: Physical theory and calculation methods, Geneva, CCITT, 1989. [7] Grcev, L., Dawalibi, F.: An Electromagnetic Model for Transients in Grounding Systems. IEEE Trans. on Power Delivery. Vol. 5. pp. 1733–1781 (1990). [8] Smith, A. A.: Coupling of External Electromagnetic Fields to Transmission Lines. New York: Wiley, 1977. [9] МКС EN 50443:2012 – Effects of Electromagnetic Interference on Pipelines Caused by High Voltage A.C. Electric Traction Systems and/or High Voltage A.C. Power Supply Systems, Brussels: CENELEC, 2011. [10] NACE SP0177-2014 – Mitigation of Alternating Current and Lightning Effects on Metallic Structures and Corroion Control Systems. Houston, Texas: NACE International, 2014. [11] Mangionem, S.: Compact Model of a Combined Overhead-Cable Line for Ground Fault Application Transfer Analysis, Proc. of the 5 th WHEAS Int. Conf. on Power Systems and Electromagnetic Compatibility. August 23–25, 2005, pp. 251–256.

System energy optimisation strategies for metros with regeneration

Energy and environmental sustainability in transportation are becoming ever more important. In Europe, the transportation sector is responsible for about 30% of the final end use of energy. Electrified railway systems play an important role in contributing to the reduction of energy usage and CO2 emissions compared with other transport modes. For metro-transit systems with frequently motoring and braking trains, the effective use of regenerated braking energy is a significant way to reduce the net energy consumption. Although eco-driving strategies have been studied for some time, a comprehensive understanding of how regeneration affects the overall system energy consumption has not been developed. This paper proposes a multi-train traction power network modelling method to determine the system energy flow of the railway system with regenerating braking trains. The initial results show that minimising traction energy use is not the same as minimising the system energy usage in a metro system. An integrated optimisation method is proposed to solve the system energy-saving problem, which takes train movement and electrical power flow into consideration. The results of a study of the Beijing Yizhuang metro line indicate that optimised operation could reduce the energy consumption at the substations by nearly 38.6% compared to that used with the existing ATO operation.

Study on Pantograph Arcing in a Laboratory Simulation System by High-Speed Photography

Phenomena of the pantograph arcing have become a challenge for the further development of high-speed electrified railway system. Despite of the large attention that has been paid to the radiated electromagnetic interference, materials ablation as well as the power-quality decline resulted from pantograph arcing, the specific dynamics of pantograph arcing with a high time resolution are still in absence. In this paper, the pantograph arcing phenomena in a laboratory simulation system were experimentally studied by high-speed photography. Synchronized electrical voltage and current waveforms were obtained to acquire a more comprehensive understanding on the underlying physics. The overall dynamics of the pantograph arcing from ignition to extinguishment were recorded. Three stages of the electric-contact process, from approaching arc, mechanical contact to the drawn arc, were well distinguished. A much intensified drawn arc was observed than the approaching arc. Typical lasting time of the drawn arcing is found $\sim 4$ times larger than the approaching arcing for our test setup. Maximum diameter of 3.3 mm was reached at around the current-peak moment. An interesting stable arc voltage of $\sim 23$ V was found during the drawn arcing. Intense material splash above the carbon strip was observed during the arcing process. The transient resistance during a typical arcing period was also analyzed, and a minimum value of $\sim 100~\text{m}\Omega $ was determined.

The Research on Main Circuit Parameters and its Control Law of TCR Single-Phase to Three-Phase Power Converter

The TCR single-phase to three-phase power converter has been widely used in electrified railway system as its simple control raw and high reliability. The research on main circuit parameters and its control law is necessary to design suitable TCR single phase to three phase power converter. This paper analyses the main circuit of TCR single phase to three phase power converter, and acquires the parameters configuration theory of each element in main circuit and control law of converter when the power factor varies from 0.7 to 0.9.

Failure Analysis of Steady Clamps Used in Electrified Railway

In this study, cracks were detected in two steady clamps made of CuNi2Si alloy after approximately 6 months of service in an electrified railway system. Efforts were made to analyze the failure of the steady clamps using both experimental and finite-element (FE) methods. Microfractography revealed the brittle nature of the fracture. No microstructural degradation was found in the failed material. Extensive flake oxides were observed in the fracture. The investigation results suggest that the root cause of the failure was overlap defect which occurred in the forging process. The association of precracks induced by overlap defect with bolt preload resulted in premature failure.

Effects of pantograph arcing on railway systems with auto transformers

Conducted and radiated electromagnetic interferences on auto transformer (AT) caused by pantograph arcing in electrified railway system are investigated. The overhead lines of electrified railway system can be simplified by three parallel overhead conductor lines. The model of AT in this paper is situated at the end of lines. The propagation of electromagnetic waves along the three conductors is solved by using finite-difference time-domain (FDTD) method. The circuit model for AT is created by state variable equations, and the equations are discretized by backward Euler method. The pantograph arcing is represented by a trapezoidal voltage pulse which has a wide band of frequency just like an arcing has; the rise and fall time are determined by the main frequency. The voltages across the AT windings are computed by the final FDTD iterative equations when all factors are considered.

Assessment of Synchronous Generator’s Influence on Transmission Network with Significant Level of Voltage Unbalance

The electrified railway systems are known as source of large voltage unbalances in the transmission network. The electrified railway connection load flow analysis provides good overview of voltage unbalance distribution over transmission network. The level of unbalance is expressed by voltage unbalance factor, which value depends on network load conditions, network strength and selected traction system solution. In this paper a fragment of Estonian transmission network is modelled in PSCAD together with perspective electrified railway system and CHP plant in order to analyse the network operation in different conditions and determine the impact of synchronous generator to distribution of voltage unbalance. DOI: http://dx.doi.org/10.5755/j01.eee.18.9.2796

Control Strategy for Shunt Active Power Filter Using Hybrid Multi-level Inverter in AC Electrified Railway Systems

The AC electrified railway systems have the power quality problems such as the harmonic current pollution and the reactive power demand, which are due to the inherent load characteristics of locomotives. The electrical nonlinearity and the single-phase moving load features of locomotives produce large amount of the harmonic current and the reactive power demand. This paper presents a shunt active power filter (SAPF) adopting hybrid multi-level inverter and a novel control algorithm based on the synchronous reference frame and the phase-shifted carrier PWM to improve the power quality in the AC electrified railway systems. The proposed SAPF and its control algorithm are investigated in the autotransformer-fed AC electrified railway application. The validity and the effectiveness of the proposed SAPF and the control algorithm are demonstrated through the case study.

Comparative Study on the Position of Shunt Active Power Filters in 25 kV AC Railway Systems

AC electrified railway systems show power quality problems such as harmonic current pollution, feeder voltage perturbation, and reactive power demand. These power quality problems have a bad effect on the AC railway system itself as well as other electric systems connected together. This paper investigates comparatively two configurations of a shunt active power filter (SAPF) for improving power quality in the AC railway systems. Different control algorithms corresponding to the installation position of the active power filter at the substation or at the sectioning post are proposed respectively. A comparative case study on the two positions of SAPF has been performed comprehensively.

Fundamental Study on Saving Energy for Electrified Railway System Applying High Temperature Superconductor Motor and Energy Storage System

Induction motor instead of dc one has been applied widely for dc electric rolling stock because of the advantage of its utility and efficiency. However, further improvement of motor characteristics will be required to realize environment-friendly dc railway system in the future. It is important to study more efficient machine applying dc electric rolling stock for next generation high performance system. On the other hand, the methods to reuse regenerative energy produced by motors effectively are also important. Therefore, we carried out fundamental study on saving energy for electrified railway system. For the first step, we introduced the energy storage system applying electric double-layer capacitors (EDLC), and its control system. And then, we tried to obtain the specification of high temperature superconductor induction/synchronous motor (HTS-ISM), which performance is similar with that of the conventional induction motors. Furthermore, we tried to evaluate an electrified railway system applying energy storage system and HTS-ISM based on simulation. We succeeded in showing the effectiveness of the introductions of energy storage system and HTS-ISM in DC electrified railway system.

Analytic Evaluation of HTS Induction Motor for Electric Rolling Stock

Induction motor in place of DC one has been applied widely for DC electric rolling stock, because of the advantage of its utility and efficiency. However, further improvement of motor characteristics is crucial in order to realize environment-friendly DC railway system in the future. It is important to study more efficient machine; applying DC electric rolling stock for the next generation high performance system. Therefore, we have carried out fundamental study on reduction of energy consumption for electrified railway system with the aid of high temperature superconductor (HTS) technology. We have firstly tried to obtain the specification of HTS induction/synchronous motor (HTS-ISM), which is target HTS motor for the aforementioned purpose. Furthermore, we have investigated the relationship between the current transport property of HTS tape conductors and the torque characteristics of HTS-ISM. As the result, we have shown the possibility of the next generation DC electrified railway system with the use of HTS-ISM.

A Novel Control Algorithm for Railway Power Quality Conditioner in AC Electrified Railway Systems

The AC electrified railway systems have the power quality problems such as the harmonic currents pollution, the reactive power consumption, and the load imbalance because the locomotives show the characteristics of nonlinear and single-phase electrical loads. These power quality problems have a bad effect on not only AC electrified railway systems but also other electric systems connected together. A railway power quality conditioner (RPQC) is able to provide a novel solution to these power quality problems in the AC electrified railway systems. In this paper, a novel RPQC control algorithm based on the synchronous-reference-frame (SRF) is proposed. The proposed RPQC control algorithm can compensate effectively the harmonic currents, the reactive power, and the load imbalance. The validity and the effectiveness of the proposed RPQC control algorithm are illustrated through the simulations.

Indirect Lightning-Induced Voltages Along a Railway Catenary-Track Multiconductor Transmission-Line System With Lumped Components

Transients caused by field-to-wire coupling due to lightning strikes in the vicinity of multiconductor transmission lines (TL) have been widely studied. In those studies, the lines represent single overhead lines, power lines, and the like with lumped loads/devices at line terminations. In electrified railway power systems, series or shunt devices, such as transformers, converters, switchgear, and signal equipments, are distributed along the TL system. In this paper, the indirect lightning effects on a typical railway catenary-track multiconductor TL system with lumped components, namely, booster and auto transformers (BT and AT systems), and track circuits, are studied. It is found that the induced voltage wave shapes and amplitudes at any point along the line are dominated by BT or AT system type, and that the voltages appearing across AT windings are higher than for the corresponding BT windings. However, the induced voltages across the track circuits are less dependent on system type and most affected by the introduction of components.

高温超電導電動機を電気鉄道に適用した電力負荷特性の向上に関する基礎検討

Induction motor instead of dc one has been applied widely for dc electric rolling stock because of the advantage of its utility and efficiency. However, further improvement of motor characteristics will be required to realize environment-friendly dc railway system in the future. Therefore, it is important to study more efficient machine applying dc electric rolling stock for next generation high performance system. For the first step, we reproduced torque characteristics of a dc motor that is utilized in an electric rolling stock, by analyzing specific current waveforms of dc substations. And then, we tried to reflect such torque characteristic to the conventional squirrel-cage induction motor based on the equivalent circuit. Furthermore, we tried to obtain the specification of high temperature superconductor induction/synchronous motor (HTS-ISM), which performance is similar with that of the above-mentioned conventional motors. We succeeded in showing the effectiveness of the introduction of HTS-ISM in DC electrified railway system.

Effects of Nonlinearities on Induced Voltages across Lumped Devices

There have been many studies on induced currents and voltages along overhead conductors due to lightning flashes. In most of these studies lumped loads and components are connected only as line terminations [1]-[4]. In studies where series and shunt connected components are connected along the lines the effects of nonlinear components and effects are disregarded [5]-[8]. This is not always correct as nonlinear effects will introduce high frequencies in the system and affect the current and voltage wave distribution. In this paper the effects of series and shunt components and nonlinear phenomenon on a system representative of the Swedish electrified railway system will be investigated. It is seen how introduction of different linear and nonlinear components affect the propagating voltage wave forms.

Experimental Verification of Induction Phenomenon on Telecommunication Lines by Applying Its Occurrence Mechanisms Using an Artificial ELF Source Generator

In this paper, an electromagnetic induction on a telecommunication line by the distribution line of a power provision system or a feeder line of an electrified railway system has been verified through experiments. The basic cause of induction occurrence by these practical power provision systems is the returning current through the earth. This principle has been confirmed by the experiments documented in this paper which implemented these mechanisms to incur an induction. Experimental methods were used to produce the returning current through the earth. The experiment to find a relationship between inducing strength and the distance between the two phase lines in a power provision line has also been included to confirm that, when the distance is enlarged, the induction effect increases as the cross-nullification effect of magnetic fluxes decreases. An experiment for the existence of a shielding effect by another conduction length material has been addedas a protection measure against the induction.

교류 전기철도 급전시스템을 위한 철도용 전기품질 보상장치의 제어방법

교류 전기철도 시스템은 비선형 단상 부하인 차량의 부하특성으로 인해 고조파 왜곡, 무효전력 발생, 3상 불평형과 같은 전기품질 문제를 가지고 있다. 이 같은 전기품질 문제는 철도 시스템뿐만 아니라 철도와 연계된 다른 건전한 계통에도 악영향을 미치게 된다. 따라서 본 논문에서는 이와 같은 전기철도 급전시스템의 전기품질 문제를 보상하기 위해 철도용 전기품질 보상장치(RPQC; railway power quality conditioner)를 적용하고, SRF(synchronous-reference-frame) 제어를 이용한 RPQC의 제어방법을 제안한다. 제안하는 제어방법을 통해 RPQC는 고조파 왜곡, 무효전력, 부하 불평형과 같은 전기품질 문제를 순시적으로 보상할 수 있으며, 시뮬레이션을 통해 이를 검증한다. 시뮬레이션 결과는 제안한 RPQC 제어방법의 타당성을 보여주고 있다.

Pantograph Arcing in Electrified Railways—Mechanism and Influence of Various Parameters—Part I: With DC Traction Power Supply

Pantograph arcing is a common phenomenon in electrified railway systems. This is also a source of broadband-conducted and radiated electromagnetic interference (EMI) for vehicle as well as traction power and signaling systems. In this paper and the companion paper, experimental analyses of pantograph arcing phenomena are presented for dc and ac feeding systems, respectively. Influences of different parameters on dc traction system, such as supply-voltage polarity, relative motion between pantograph and overhead contact wire, namely, forward motion along the track (longitudinal), and lateral sliding motion of the pantograph (zigzag) are presented here. From the voltage and current waveforms of the test runs, it is shown that pantograph arcing is a polarity-dependent phenomenon. For the positive-fed overhead traction system, where pantograph is cathode, the supply interruptions due to zigzag motion are comparatively less compared to negatively fed traction systems. As a result, the transients, due to pantograph arcing, are more frequent in negatively fed traction systems. It is found that the arc root movement along the electrode surfaces (pantograph-contact wire) is governed by the relative motion and polarity of the electrodes. The analyses presented in this paper also form a foundation to understand the pantograph arcing process and the corresponding influential parameters with the ac supply presented in the companion paper. The findings presented in this paper could be beneficial for coming up with appropriate mitigation techniques from the EMI due to pantograph arcing in dc-fed traction systems.