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DC electric power systems, including HVDC, HVDC light, dc distribution systems, and dc microgrids, have a significant position in present and, especially, future electric power systems, namely, smart grids. One of the most significant issues of electric power systems, including dc electric power systems, is the calculation of accurate and fair energy costs of the consumers. In this paper, novel, simple, practical, and precise relations between economic and electrical variables in dc electric power systems are extracted. The novel relations prove that there are interesting relations between voltages of nodes, as electrical variables, and prices of nodes, as economic variables, in dc electric power systems. Applying the extracted novel relations in this paper, a new, fair, precise, practical nodal price, i.e., the fair nodal price, is determined to calculate the energy costs of consumers in dc electric power systems, including dc distribution systems and microgrids. Moreover, as an application of the extracted novel relations, a practical method to determine the fair nodal prices of all nodes and, as a result, the real energy cost of each consumer at each node of dc electric power systems is presented. The analyses results demonstrate the mentioned significant characteristics. [ABSTRACT FROM AUTHOR]

Currently, in electric railways, the old dc supply systems are reaching their limits. In several European railway networks, due to the line-voltage drops between substations, there are several sectors where traffic can no longer increase and where locomotives cannot operate at their nominal ratings. To improve the power capacity, a medium voltage dc (MVdc) three-wire supply system with voltage boosters based on imbricated cell multilevel choppers (ICMC) was proposed. In order to increase efficiency, the authors evaluate the potential of new SiC-mosfets in this topology. An opposition method test bench using two ICMCs was built with 1.7-kV/300-A half-bridge modules. The design of the multilevel converters takes into account the constraints related to high switching frequency operation (up to 50 kHz). Thanks to the opposition method, losses in ICMCs can be determined by electrical and thermal measurements with good accuracy. Finally, solutions with SiC-mosfets and Si-insulated gate bipolar transistors are compared in terms of efficiency. [ABSTRACT FROM AUTHOR]

The line-side converter, which can represent an ac–dc–ac drive electric vehicle when analyzing the low-frequency oscillation in electric railways, is modeled in dq frame with the proposed single-phase dq-decomposition method. With this model, an underdamped mechanism of the vehicle-grid interaction is confirmed. Besides, a low-frequency stability prediction approach is presented, based on the dominant-pole analysis and verified by the simulation and the testing result. The proposed modeling method and prediction approach benefit in three aspects: It is more convenient to rebuild the model with a change of either the line-side converter controller or the system condition, much quicker to predict the low-frequency instability and more explicit to guide the modification of the controller software to damp the low-frequency oscillations. [ABSTRACT FROM AUTHOR]

Balance transformers can usually eliminate the zero sequence current and suppress the negative sequence current. This paper develops a novel approach for balance transformers, which is different from the traditional one with two-phase or three-phase symmetrical windings. First, the basic principle and the connected scheme of the transformer are clarified. Second, this paper derives the relationship between the primary and the second windings from a mathematical model for the new approach. Third, the balance condition (i.e. the neutral current in the primary side is zero) and the decoupling condition of the two-phase system are also obtained. Finally, the correctness and feasibility of the new approach are verified by the experimental results of a 1-kVA model transformer. Compared to the traditional balance transformers, the new approach has better performance and can be applied to the two-phase or single power supply, such as the traction power supply in electric railway. [ABSTRACT FROM AUTHOR]

The problem of optimally sizing hybrid energy storage systems (HESS) installed in electric railway systems, considering the effect of regenerative braking is studied in this paper. HESSs combine traditional batteries and newly developed ultracapacitors, taking advantage of the high energy capacity of batteries and of the flexibility and ability to capture high power density of ultracapacitors. A novel mixed integer linear programming formulation that includes the counting of battery cycles is presented. Some particularities of battery operation are included in the model, like the dependence of its performance on the number of cycles and the depth of discharge (DOD). Results are reported first for a illustrative case study, allowing us to perform sensitivity studies for several parameters; results are also reported and for a larger case, closely resembling the problem faced by railway energy systems planners and operators. [ABSTRACT FROM PUBLISHER]

Facing the challenges brought by the negative sequence current (NSC) pollution in power supply system of electric railway, a new topology named half-bridge winding compensation-based railway power conditioner (HBWCRPC) without auxiliary step-down transformer is proposed to suppress the NSC injected into the public networks. It has the advantages of high integration, low losses, and more functions. The compensation principle is discussed, and its physical interpretation is presented. Besides, the mechanism of the voltage perturbation and its various representations in steady state are analyzed. Considering the complexity of voltage perturbation, an optimal control method is adopted to improve the robustness of the control system, and a linear quadratic regulator with integral action, which is applicable for this system, is designed. Finally, simulation and experiment results validate the HBWCRPC system and its control method. [ABSTRACT FROM AUTHOR]

This paper presents an easy and a robust sensor fault detection and isolation (FDI) and fault tolerant control (FTC) of a single phase PWM rectifier for electrical railway traction application. Catenary current sensor and dc link voltage sensor failures are considered. The FDI method is based on observers and residual generation. The different FDI algorithm steps allow a good detection and isolation of the sensor fault and identify the faulty sensor. The reconfiguration strategy consists of two steps with open loop control and closed loop control working. Simulation results are presented to illustrate the good performance of the FTC procedure. Experimental results are also presented to show the effectiveness of the proposed FDI and FTC algorithms and good performances of the rectifier after the reconfiguration. [ABSTRACT FROM AUTHOR]

Abstract: For novel design and efficient operation of next-generation DC electric railway systems, especially for their substantial energy saving, we have studied the feasibility of applying superconducting power cables to them. In this paper it is assumed that a superconducting power cable is applied to connect substations supplying electric power to trains. An analysis model line was described by an electric circuit, which was analyzed with MATLAB-Simulink. From the calculated voltages and currents of the circuit, the regenerative brake and the energy losses were estimated. In addition, assuming the heat loads of superconducting power cables and the cryogenic efficiency, the energy saving of the total system was evaluated. The results show that the introduction of superconducting power cables could achieve the improved use of regenerative brake, the loss reduction, the decreased number of substations, the reduced maintenance, etc. [Copyright &y& Elsevier]

In this paper, we propose a protection scheme using a superconducting fault current limiter (SFCL) for the electric railway with traction power supply system with the automatic power changeover switch (ACS) system. The Korean electric railway uses a Scott transformer with many traction power substations. Each traction power substation has a neutral section. The ACS system is being installed at the neutral section and studied. In this system, shorting between the M- and T-phases prevents phase-to-phase faults, which was not considered for the conventional AC railway, due to the ACS. The proposed protection scheme using the SFCL mitigates this problem. In addition, we analysed the effect of the proposed protection scheme using the time-domain transient simulation software PSCAD/EMTDC. [ABSTRACT FROM PUBLISHER]

In this work is presenting the study of the electric current's parameters and characteristics, obtained by means of an electric power's quality analyzer. The measurements were made into an AC railway electric traction substation of 27 kV, during more hours, being registered momentary and average values. The data acquired with the electric power's quality analyzer were registered into a computing system, for their further analysis. In order to achieve the adaption between the analyzer's input measures and the traction line's values, the measurements were made in the secondaries of the voltage and current transformers existent in the traction substation. [ABSTRACT FROM AUTHOR]

A multi-purpose balanced (MPB) transformer is proposed in this paper for electric railway applications. The MPB transformer is developed from impedance-matching (IM) transformers widely used in China's railway systems. The proposed MPB transformer has three main functions: 1) it provides a symmetrical two-phase voltage of 27.5 kV for railway overhead lines to power electric trains; 2) it supplies a three-phase balanced voltage of 10.5 kV for railway substations; and 3) it can accommodate a three-phase harmonic filter with improved power factor and reduced manufacturing cost. In this paper, the operating principles of the MPB transformer are elaborated, the design of the harmonic filters is discussed, and the results of computer simulations are provided. A 16-MVA MPB transformer was designed and commissioned, and real-time field measurements are provided. [ABSTRACT FROM AUTHOR]

The problem of determination of the accurate distribution of the return current in AT (autotransformer) electric traction systems (supplied at 2 × 25 kV) for High Speed Railways is considered. The path of the traction return current flowing from the rolling stock axles back to the supply (i.e., substation) is composed of the traction rails and additional earth potential conductors. The overhead supply conductors in contact with the train pantograph are connected to a symmetrical circuit (the feeder) with the purpose of current balancing. This arrangement and its influence on current to earth are considered: the return current divides among rails (as signalling disturbing current) and earth, depending on the value of the electric parameters of the system and the earth and on the circuit arrangement and on the relative position of system devices. The amplitude (as a percentage of the total return current) of the disturbing current may be high enough to cause interference to signalling. This work investigates the behavior of the return current in AT electric railway systems, on the basis of a reference system for the variation of the most important electrical parameters. [ABSTRACT FROM AUTHOR]

The problem of the determination of the real distribution of the return current in electric railway traction systems is considered. One or more conductors (depending on the specific supply system) are purposely set up to carry the traction return current flowing from the rolling stock axles back to the supply (i.e., substation); yet, part of the return current flows through signailing conductors (disturbing current) and through the earth, depending on the value of the electric parameters of the system, on the circuit arrangement, and on the relative position of the supply, the rolling stock, and signalling devices. The amplitude (as a percentage of the total return current) of the disturbing current.may be high enough to cause interference to signalling. This work investigates the behavior of the return current in ac and dc electric railway systems, on the basis of a reference system for the variation of the most important electrical parameters. The definition of the transfer function between the return current and the signaling circuit variables is an important element for the compatibility analysis between train detection systems, rolling stock and infrastructure, to promote the cross-acceptance of rolling stock in Europe and abroad. [ABSTRACT FROM AUTHOR]

This article examines the role of public service employees in politics. One of the arguments used in favor of municipal ownership is that privately owned public utilities are a source of political corruption. However the author John R. Commons and others have pointed out that there is a tendency for labor groups to take a more active part in politics under municipal ownership than when employed under private management. In 1919, as the result of a popular vote, the city of Seattle purchased the entire holdings of the private traction monopoly for the sum of $15,0000,000. The street railway employees had organized a union and successfully conducted a sixteen day strike two years previously. At the time of the election they took a decidedly active part in persuading the citizens to vote for the purchase of the system. Each man was asked to secure as many votes as possible. Since the date of the purchase of the street railway system by the city there have been three elections for major and one special election concerning a proposed change in the form of the city government to a city manager plan.

The article discusses the ownership issues and legal disputes associated with the street railways of Detroit, Michigan. An investor in street railways, R.T. Wilson was the owner of the railway system managed by Tom L. Johnson, a street railway manager and manufacturer of street rails. The railway system was completely redesigned after a major fire in such a way that all the main lines pass at a given point which facilitated easy commuting. An act was passed in 1899 to create a Detroit Street Railway Commission empowered to buy or lease any street railways from various companies to maintain and operate them. It was considered to grant the ownership to city but length of the lease led to legal disputes and any final decision was yet to be reached.

The article offers news briefs related to various developments in the field of economics across the world as of July 1, 1898. Information on the courses that will be offered by college teacher William Cunningham at Trinity College in Cambridge, England is presented. The British government has appointed an Indian Currency Committee for establishing gold standard in India. Brief information about the content of the report of the Massachusetts Commission on Street Railways is presented.

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. [ABSTRACT FROM PUBLISHER]

A railway derailment is usually an unpredictable event where the damage could range from a simple train delay to a big loss of goods, assets (rolling stock and permanent way) and, in extreme cases, even human lives. Therefore, Brazil’s railways are always implementing actions that minimize the risk of a derailment. One of the main actions is to establish tight maintenance criteria for rolling stock and for track geometry. However, these criteria usually do not consider the vehicle dynamics and the geometry of the permanent way together. Thus, this paper develops a mathematical model of a high capacity railcar together with the flexible support of the track to determine a method of assessing bounce, roll and pitch motions from instrumented wagons, so this method can be used in routine inspections. The mathematical model was satisfactorily validated by comparing the natural frequencies obtained from the model and from a real vehicle tested in the field. In addition, the model results were compared against field measurements from an instrumented wagon and a track geometric vehicle. A strategic method for operational safety analysis was suggested and used, which was able to determine the wavelength of permanent way anomalies that should be given priority for maintenance actions as well as considered when adopting speed restrictions. [ABSTRACT FROM PUBLISHER]