TRACK CIRCUITS INTERFERENCE RESISTANCE INCREASE UNDER THE TRACTION CURRENT INFLUENCE

Several publications have been devoted to the development of traction power supply for alternating current [1, 2]. They set the task of considering the resistance of the external power supply system and power traction transformers when calculating the current distribution in traction networks. With all the merits of the existing methods for calculating these resistances, there are discrepancies in the published sources in determining the parameters of the equivalent circuit for the traction power supply system [3, 4, 5, 6]. In the present work, the authors propose a technique for calculating reduced to a voltage of 27.5 kV equivalent resistances of an external power supply system and a power traction transformer. An equivalent circuit for replacing the traction power supply system is substantiated, allowing to take into account the voltage drop on the overall resistance of the external power supply system from the traction currents of the considered and adjacent feeder zones, as well as transit currents flowing through the power lines. Using the method of symmetrical components it was obtained that when calculating the internal resistance of a traction substation consisting of the resistances of the longitudinal power supply line and the power traction transformer, it is necessary to use the calculated formulas obtained when taking into account the actual current distribution in the secondary (traction) winding of the power traction transformer. It is shown that the traction network equivalent circuit for the calculation of short-circuit currents, given in [1, 2], does not reflect the real current distribution relationships in traction networks. The main reason for the inconsistency of the scheme proposed by a number of experts with the existing traction power supply system is determined by an unjustified transition from an asymmetric system “three-phase transmission line - transformer - power supply system - single-phase traction network” to a single-line calculation scheme. When calculating the current distribution according to this scheme, there is no metallic connection of the track with one of the phases (more often phase C ) of the power traction transformer. The absence of this connection leads to the flow of traction currents between the district and traction substations, short-circuit current on the ground, which is not permissible.

Purpose of the work is improved approaches to ensure the required quality parameters of voltage in the traction network based on modern technologies and equipment in the application of power distribution system. Actuality. The introduction of high-speed traffic, increase weight standards Train necessitates increasing the carrying capacity of railways. Often the carrying capacity of existing sections electrified at 3.0 kV DC power supply unit limits. Such limitations include voltage decrease on the electric current collector below the allowable value for the normal operation of 2700 (2900 for high-speed V) and heating the contact wires, thereby losing their mechanical strength. Existing power supply system of RS, which have considerable installed traction substations, can not provide the required level of power density traction network for high-speed movement within 1.5 - 2 MW / km and, respectively, the required voltage quality. At the same time, the daily loading of a powerful traction substations in providing intensive schedule of trains does not exceed 20-25%, while the energy loss in traction network peak load increases and reaches 10-15% of the energy consumed. Thus, the existing system of power traction networks is not sufficiently effective and economical, even with the application of existing methods to strengthen them. In our view, the main limiting factor for a given quality of voltage in the traction network is the use of centralized power. From this, the development of measures to improve the quality of voltage in the traction network in the implementation of high-speed traffic in a growing scarcity of energy resources is an urgent task. Scientific novelty. Using distributed power supply system with adjustable supply points combined into intelligent power supply, which enables adaptive change the characteristics of the transfer, conversion and consumption and optimize the mode of functioning of the traction power supply is suggested for improving the quality of voltage in the traction network in the implementation of high-speed and heavy traffic. Practical significance. Improving the quality of voltage in the traction network by using the proposed circuit design traction power supply will ensure the desired mode voltage and power characteristics of the traction network in the implementation of high-speed and heavy traffic while reducing electricity losses by 20-30%.

In the traction power supply system (TPSS) of the high-speed railway (HSR), the traction load produces extremely severe load conditions. Therefore, Gas insulated substation (GIS) equipment served in TPSS of HSR suffers from both progressive degradation and random shocks. In this paper, the failure model of GIS equipment is considered as a competing failure mode multiplied by these two failure mechanisms. The degradation process and the shock process are described by gamma process and compound Poisson process, respectively, based on their temporal and spatial randomness. Furthermore, the maintenance strategy for GIS equipment in long-run time span with periodic inspections is developed. Under comprehensive consideration of optimal reliability and economic efficiency, indices associated reliability and maintenance cost are defined to evaluate the maintenance strategy performance in long-run time span for GIS equipment. The analysis results in the case study show that the inspection period and the shock threshold, as two maintenance decision parameters, can be optimized to achieve both high reliability and low maintenance cost. The influences of failure model parameters on optimized maintenance strategy are also revealed.

Predicting the system behavior of traction power supply systems, earthing systems and track circuits have become of vital importance to the railway community. The availability of computer based tools is a precondition in engineering studies in the field of electrical systems compactibility (ESC) and electromagnetic compatibility (EMC). Also, the sharing of information among multiple parties involved in activities on a single segment of infrastructure has become more and more important. Multiple cases have demonstrated this need for cooperation. Since 1994 simulations and measurements on the behavior of AC traction power supply systems have been made by Holland Railconsult. Also, its influence on signaling and telecommunication systems as well as on existing railway infrastructure and third parties are studied. In the course of this process the necessity to have a dedicated simulation tool available became clear. After several years of development, a useful simulation tool is now available. The newly desgined web-implementation makes it possible to access the SimspoG tool through the Internet by a common Internet Browser. The SimspoG User application interface implementation allows for inputting or modifying different simulation model parameters and starting of simulation processing.

The problem of increasing energy saving and energy efficiency in the system of traction power supply of the Moscow Metro is considered due to the use of energy storage devices of uncontrolled type. The results of simulation modeling of the operation of an energy storage device of uncontrolled type in the system of traction power supply of the subway are presented.A particular line of the Moscow Metro, Filevskaya, was studied, on which experiments on the introduction of energy storage devices based on electrochemical super capacitors were conducted.With the help of experimental measurements, the electric power indicators of the operation of a stationary energy storage device had been obtained at regular service on the traction substation of the Filevskaya line of the Moscow Metro for several months. The maximum levels of the converted energies, the cyclicity, the efficiency of the plant operation, and the amount of the energy economy are determined.By statistical processing of the instantaneous values of the performance of the traction substation with the accumulator and the analysis of the data of the energy monitoring of the Moscow metro, an important parameter of reducing the installed capacity was investigated. The similarity of the data of theoretical calculations and experimental measurements is shown.

The urban railway systems using state-of-the-art technologies for train traffic, safety, traction and rail infrastructure are becoming increasingly widespread in the world. The Moscow Central Circle railroad is an example illustrating their integration into the urban transportation system of a megacity.Development and continuous modernization of such railroad systems during their operation generate new innovative approaches, particularly in the field of electric power supply.Electric traction load on the traction electric power supply system of the Moscow Central Circle railroad has several features explained by prevalence of passenger traffic and frequent changes of operating modes of electric trains. Frequently used regenerative braking determines the statement of the problem of developing a complex of measures to increase the efficiency of traction power supply system measured by the criterion of output capacitance reduction and of energy efficiency indicators’ growth. The use of electric energy storage systems within the traction power supply system can help to solve thementioned problem.The objective of the described research is to assess the efficiency of the implementation of the electric energy storage devices within the system of traction power supply system of the Moscow Central Circle. The research uses the methods of statistical processing of the measurement data and of simulation modelling. Simulation modelling of interaction of electric rolling stock with traction power supply system within the Moscow Central Circle allows to obtain the characteristics of load chart of electric energy storage systems and of bus voltage at sectioning posts, to evaluate the durations of operation cycles in charge and discharge modes, their number and relevant total amount of electric energy per day.The obtained results allow assessing the technical features of various types of electric energy storage devices regarding operating conditions within traction power supply system of the Moscow Central Circle and to determine the economic efficiency of their implementation.

The object of the study is the process of operation of traction and external power supply systems as objects of inextricable interconnection while reducing energy costs in the cost of railway transportation in real time. One of the most problematic areas is the technology for choosing energy-efficient power supply schemes for railway traction networks in real time. The methods of forming and transforming graphs of complex schemes of traction and external power supply systems and building expert control systems for the implementation of energy-saving technologies of electrified railways were further developed in the work. In the course of the study, to increase the efficiency of simulation modeling of electric traction networks, the statistical characteristics of the loads of feeders that supply the final boundary sections, stations, depot access tracks, railway junctions and idle voltages on the traction substation tires were obtained. Methods of calculation and modeling of traction power supply have been developed, which take into account the inseparable relationship with power systems and allow choosing rational modes with minimal power flows and energy losses. Proposed methods of managing the modes of operation of the traction power supply system based on a vague description of their states and an expert system that allow solving new problems. Including, the choice of energy-saving power supply schemes in the case of power flows, economic modes of network operation in case of intensification of the transportation process. Thanks to this, ways of reducing power consumption and minimizing energy losses of traction power supply systems are proposed, which allow minimizing power flows and power losses by adjusting load flow parameters and voltage levels of traction substations. And also to increase the energy efficiency of electrified railway lines. The technique of technical and economic feasibility of power supply schemes of traction networks and evaluation of the possibility of switching to cantilever or loop power supply schemes with parallel connection points has been developed. The implemented recommendations save about 25 thousand kWh per 1 km of two-track section.

The rail potential is the voltage between running rails and earth under operating conditions when the running rails are utilized for carrying the traction return current or under fault conditions. Main characteristics of high-speed railway traction load are high-power and high operating currents. It may cause rail potential to exceed limits and endanger the safety of persons. So it is worth studying that how to keep the rail potential below a critical value under all expected conditions. The models of return circuit system of traction power supply system (TPSS) of high-speed railway are built using SimPowerSystems toolbox provided by MATLAB/SIMULINK in this paper, and the simulation results are given out. Based on compare and analysis, several factors that have obvious influence on rail potential are pointed out, such as the conductance per unit length between running rails and earth. The effects of some measures to low rail potential are also compared and a reasonable scheme is brought forward. It is illustrated that the scheme may ensure safety of persons through simulation

Adequate protection scheme is an important defense mechanism for traction power supply system (TPSS), and the reliability of its operation could affect the normal operation of the system. Therefore, in order to maintain the system in safe operation, it is of great importance to quantify the influence of protection scheme on traction power supply system. This paper presents a risk assessment method for traction power supply system considering the reliability of system protection. A risk probability model for system protection is established. Based on Markovian state-space method, the reliability of the protection system is evaluated; the misoperations of the protection system and their possible consequences are analyzed by FMEA method. Three types of economic loss indices are defined to establish the quantitative risk consequence model; the risk of traction power supply system is thereby quantified by integrating risk probability and risk consequence. Practical traction power supply system is taken as an example to prove the effectiveness of the proposed method. The evaluation results can help formulate corresponding measures, and provide guidance for maintenance strategies, thus reducing system risk.

The Smart Grid network system is a concept of a fully integrated, self-regulating and renewable electric power system, which has a network topology and includes all generating sources, trunk and distribution networks and all types of electric energy consumers, managed by a single network of information and control devices and systems in real time mode. The article proposes the introduction of the Smart Grid concept into the traction power supply system of railways. The functional properties and technical solutions that will allow implementing the principles of Smart Grid intelligent power supply systems are considered. A comparative description of the functional properties of the existing energy system and the energy system based on the Smart Grid concept is presented. Possibilities of introducing Smart Grid into the traction power supply system of direct current due to increasing the carrying capacity of trunk networks, consumption management, location of distributed energy sources in distribution networks and closer to consumers have been determined. The limits of the energy-saving effect from the introduction of the Smart Grid concept into the traction power supply system have been determined.

As the motivation in developing modern MRTS and the upgrading of old systems in many metropolitans all over the world, especially for public transportation in developing countries, the demand to simulate the dynamic traction power supply system (TPSS) more effectively and practically has increased. This paper describes the work of simulating and analysing TPSS. It is based on dependent train movement in conjunction with TPSS simulation to establish a panorama view of the features. The free time scheduled strategy for train movement is applied which is more flexible and effective to reflect operation strategies. To set up the dynamic TPSS structure with respect to the moving train status for the system solution, the schematic arrangement is split into four parts: establishment of the elementary electric network framework; establishment of the dynamic electrical network structure which includes both the elementary power network and the moving trains statuses; dynamic electric network simulation; and system analyses based on the panoramic features drawn from the simulation. The simulation results are based on the Shanghai Metro Line One (excluding the extension section). Simulation and analysis on more lines including Shanghai Line Two and Guangzhou Line One MTRS have also been implemented using similar approaches. The complete profiles of the TPSS provide a practical means in analysing the system configuration as well as organizing the system operation.

The traction power supply system is one of the most important parts of a railway system, which is responsible for providing electricity to power the running trains and other operating equipment. The performance of the power supply has a profound impact on the railway system. Therefore, it is necessary to conduct research on the reliability of the power supply system considering traction load and ensure it is highly reliable. This article introduces some reliability-related indexes based on the fault tree analysis (FTA) method and proposes a method to evaluate the system reliability of a dc-electrified railway. The effect of traction load on power supply system reliability is studied based on Institute of Electronics Engineers (IEEE) standards. A dynamic reliability and life evaluation model is built up to evaluate the reliability of traction substation and to develop a plan to reduce the operational risk of the power system. Through analysis of a practical example of the Singapore East-West line, the system reliability and remaining useful life of each traction substation are obtained. The outcome from this study provides guidance for the maintenance and future operation plan of the power system.

The main trends of technical development and improvement of dc traction power supply systems are considered. Methods and programs are developed that make it possible to study the electromagnetic processes in rectifier–inverter units of traction substations and the self-excited source voltage inverter of induction traction drive and determine and predict the levels of harmonic components of the current in both dc–ac converters themselves and that in the traction network. This makes it possible to determine the electromagnetic effect of various power semiconductor converters on communication devices and railway automation and ground the choice of circuits and protection parameters ensuring electromagnetic compatibility. Analysis and synthesis of electromagnetic processes and the main characteristics of multipulse converters reveals that 24-pulse rectification circuits with serial connection of three-phase bridges are the most effective for a dc traction power supply system with a 24-kV voltage traction network. The introduction of 24-pulse rectifiers makes it possible to decrease power loss in the traction network and reduce the consumption of reactive energy from the primary power supply system. These rectifiers provide not only an increase the traction substation efficiency, but also refinement of electric energy in the primary power supply system and traction network. The latter makes it possible to use simpler and more economical smoothing filters that ensure electromagnetic compatibility of the new dc traction power supply system with communication devices, railway automation, and other infrastructure.

The problem of railway transport electromagnetic compatibility automation systems in recent years has been aggravated by the use of power frequency converters in electric transport drives, which significantly increase the efficiency of traction characteristics of 3-phase electric engine. However, estimate relevant harmonic levels in the frequency range used in track circuits of railway automation and telemechanic systems. The paper provides theoretical justification for practical measurements of interference. It is shown, that the interference coefficients monotonically increase in the following cases: 1) increase in the value of the harmonic frequency; 2) increase in the propagation constant, taking into account the supports resistance of the contact network; 3) increase in the circuits track length. Operating frequencies of tonal track circuits up to 800 Hz, the interference increase rate in given length of the rail circuit slows down. The increase in interference coefficients depending on the mentioned factors is explained by the fact that with current part growth of the harmonic flows from the traction substation through the earth increases and thereby creates currents asymmetry of the track circuits.

The cable is an essential pivot of electric energy transmission, and its operational condition influences the safety and stability of both the power system (PS) and traction power supply system (TPSS). The prompt detection of cable insulation conditions by partial discharge (PD) monitoring is crucial for mitigating potential damage to the cables. To begin with, this article provides a comprehensive overview of PD detection approaches for cables by introducing the mechanism of PD in cables. The detection approaches are categorized into electrical detection techniques and nonelectrical detection techniques. Afterward, to accurately assess the insulation condition of cables using the PD detection method, this article summarizes the insulation defect diagnosis approaches for cables. In particular, the insulation defect diagnosis approaches primarily comprise extraction and optimization for features, traditional machine-learning-based fault diagnosis approaches, and deep-learning-based fault diagnosis approaches. To conclude, this article summarizes the challenges and future research directions of cable fault diagnosis. Accurate cable fault diagnosis is fundamental to maintaining the reliable operation of cables, ensuring an uninterrupted power supply to both PS and TPSS, and enhancing the responsiveness to equipment failures.