Traction Currents Research Articles

Deciphering Nano-Resolution Petrological Characteristics of the Siliceous Shale at the Bottom of the Longmaxi Formation in the Zigong Area, Sichuan Basin, China: Deep-Water Microbialites

Three nano-resolution petrological microtextures were discovered in the siliceous shale at the bottom of the Longmaxi Formation in the Zigong area, Sichuan Basin. Based on observations of the occurrences of the minerals, organic matter, and organic matter pores in the different microtextures and analysis of their relationships by means of nano-resolution petrological image datasets obtained using the Modular Automated Processing System (MAPS 3.18), the formation mechanism of the siliceous shale was studied. The results show that the strong modification of clay-rich sediments by a deep-water traction current was the basis for the formation of the siliceous shale. The clay-rich sediments were converted into flocculent sediments rich in oxygen and nutrients via agitation and transport by the deep-water traction current, providing space and a material basis for microbes to flourish. Under the continuous activity of the deep-water traction current, the clay-rich sediments were transformed into microbial mats, in which in situ terrigenous detrital quartz and feldspar, endogenous detrital calcite, authigenic dolomite, and dolomite ringed by ferrodolomite were scattered. During the burial stage, the microbial mats were lithified into the siliceous shale composed of three petrological microtextures. Microtexture I was mainly transformed by microbes. Microtexture II was formed via lithification of the residual clay-rich sediments. Microtexture III was composed of migratory organic matter filling hydrocarbon-generating pressurized fractures. Due to the universality of deep-water traction flow and the diversity of microbes in deep-water sediments, we firmly believe that more and more deep-water microbialites will be discovered worldwide through systematic characterization of nano-resolution petrology with the booming development of the shale gas industry.

Localization Method for Insulation Degradation Area of the Metro Rail-to-Ground Based on Monitor Information

Since rail-to-ground insulation decreases, large-level direct currents (DCs) leak from railways and form metro stray currents, corroding the buried metal. To locate the rail-to-ground insulation deterioration area, a location method is proposed based on parameter identification methods and the monitored information including the station rail potentials, currents at the traction power substations (TPSs), and train traction currents and train positions. According to the monitoring information of two adjacent TPSs, the section location model of the metro line is proposed, in which the rail-to-ground conductances of the test section are equivalent to the lumped parameters. Using the rail resistivity and traction currents as the known information, the rail-to-ground conductances are calculated with the least square method (LSM). The rail-to-ground insulation deterioration sections are identified by comparing the calculated conductances with thresholds determined by the standard requirements and section lengths. Then, according to the section location results, a detailed location model of the degradation section is proposed, considering the location distance accuracy. Using the genetic algorithm (GA) to calculate the rail-to-ground conductances, degradation positions are located by comparing the threshold calculated with the standard requirements and location distance accuracy. The location method is verified by comparing the calculation results under different degradation conditions. Moreover, the applications of the proposed method to different degradation lengths and different numbers of degradation sections are analyzed. The results show that the proposed method can locate rail-to-ground insulation deterioration areas.

Computational analysis of electromagnetic field exposure in passengers near high- current contact wire environments.

The electromagnetic environment of a railway station is composed of electrical, magnetic, and electromagnetic fields, which are generated by various sources such as traction current, voltage, pantograph-catenary arc, locomotive braking, wheel-rail rolling arc, and communication systems. However, there is public growing concern among the public about the potential negative human health effects of this electromagnetic environment. To analyze the distribution of electromagnetic fields in human tissues, electromagnetic simulation software is used to create a model that includes six track contact wires and four waiting passengers on three platforms. This model is used to analyze the magnetic field environment created by high currents in the contact wires of a multi-track high-speed railway station. By varying the loads on different contact wires, the distribution of electric field and magnetic flux density within human tissues of waiting passengers on different platforms is studied using this model. When the track is unoccupied, the calculation results show that the maximum values of the electric field and magnetic flux density of the passenger's human body tissue at the blind way on the platform and 1m of the blind way are 17.6mVm-1 and 52.7 μT, respectively. These values increase by 9.28mVm-1 and 16.4 μT compared to when the track is occupied. When more contact wires are loaded with currents, the electric field mode and magnetic flux density mode of human tissues increase at the same position on the platform. Specifically, when the contact wires of six tracks are loaded with current at the same time, the maximum values of the electric field mode and magnetic flux density mode of the waiting passengers' human tissues at the blind way on different platforms are 29.6mVm-1 and 88.1 μT, respectively. These maximum values are lower than the public electromagnetic exposure limits that are designated by the International Commission on Non-Ionizing Radiation Protection guidelines. The research results demonstrate that the magnetic field environment generated by the current in the contact wires of a railway station with six tracks does not pose a health risk to human tissues of passengers waiting at the blind way and 1m of the blind way on the platform. These findings can provide valuable data reference for the formulation of relevant standards for the design of electrified rail transit, as well as the suppression of electromagnetic interference and protection of human bioelectromagnetism.

An Energy Management Method for Magnetic Field Energy Harvesters Under Wide-Range Current in Railway Electrification Systems

The wide-range traction current brings great challenges to the stable operation of the magnetic field energy harvester (MFEH). Specifically, when the traction current is large, the core saturation increases, resulting in violent vibrating of the magnetic core. When the traction current is low, the energy harvested by the MFEH is insufficient to power the load. To address these vital problems, an energy management method for MFEH is proposed to track the critical saturation point, i.e., the maximum power point in the unsaturated region. In this method, by regulating the equivalent load, the core voltage is controlled at the critical saturation voltage under different current levels. Moreover, the supercapacitor is employed to store excess energy at large currents, and the stored energy is released at low currents. Furthermore, a design procedure for the core and winding is proposed in this work, which can be used to adjust the critical saturation voltage of the MFEH. A laboratory prototype is built to verify the effectiveness of the proposal. The results show that the MFEH can operate at the critical saturation point and provide stable energy for the load under different current levels. This means that saturation suppression, maximum power point tracking, and energy management can be realized by applying the proposed method.

Mixed siliciclastic-carbonate-tuffaceous sedimentation in a rift lacustrine basin: A case study of the Lower Cretaceous Jiufotang Formation in the Luxi sag, Songliao basin

The Lower Cretaceous Jiufotang Formation lacustrine successions in the rift Luxi sag, Songliao Basin are characterized by mixed siliciclastic-carbonate-tuffaceous and organic-rich deposits. Ten facies were recognized and were formed in fan delta, delta, littoral-sublittoral lacustrine and deep lacustrine environments. A depositional sequence characterized by significant changes in facies and lake regime has been defined, and is divided into lowstand systems tract (LST), transgressive systems tract (TST), and highstand systems tract (HST) that are separated by sequence boundaries, initial flooding surfaces, and maximum flooding surfaces, respectively. During the LST, the delta and fan delta deposits covered the marginal area and extended into littoral-sublittoral lacustrine and deep lacustrine environments, respectively. During the TST, the areas of delta and fan delta decreased and lake areas increased, and the carbonate-dominated shoals and mixed siliciclastic-carbonate shorelines occupied the edge of the Majiapu highland belt. During the HST, the lake areas further expanded, and the fan delta deposits extended into deep lacustrine environments and formed deposits of underflows and turbidites. A depositional model in the rift lacustrine Luxi sag is proposed, incorporating the effects of tectonics and sediment supply, climate and carbonate production, hydrodynamic conditions, and lake-level fluctuations. During the LST, the active tectonic movement, high input of siliciclastic sediments, and subaerial volcanic eruptions resulted in the wide distribution of mixed siliciclastic-tuffaceous sedimentation. During the TST, the brackish lake water controlled by periodic dry and hot climate facilitated the carbonate deposition in shallow water, and tractional currents onto the lake shore carried sediments to form the mixed siliciclastic-carbonate-tuffaceous facies. During the HST, more humid climate and increased runoff allowed formation of widely distributed, mostly oil shale-rich deposits, and the gravity flows carried the sediments into the deeper part of basin to form the mixed siliciclastic-carbonate-tuffaceous facies. The depositional model of mixed deposits in this rift lacustrine basin has been proposed here in order to encourage comparison with other similar basins.

Analysis and suppression of operational overvoltage and inrush current for high‐speed trains by automatic phase‐switching technique

AbstractWhen a high‐speed train approaches the insulated phase‐splitting section embedded between neighbouring power supply arms, the vacuum circuit breaker (VCB) installed on trains must be disconnected to maintain the traction power supply system as a no‐load condition for completing phase‐switching action, as the train passes through the phase‐splitting section depending on its inertia. However, when operating VCBs, the arc is easily triggered between the mobile contacts inside, accompanied by an overvoltage impulse. Herein, to explore the generating mechanism of inrush current and operational overvoltage, a model describing the ‘substation‐catenary‐train’ traction power supply system is launched based on an equivalent circuit modelling technique. Through the analysis of the transient VCB operational process, the phase of catenary voltage is directly related to the characteristics of the VCB switching‐on overvoltage, as the traction current's phase angle is relevant to the amplitude‐frequency characteristics of the VCB switching‐off overvoltage. Inrush current as a noteworthy element is related to the traction transformer's remanence. The automatic phase‐switching technique is utilised to suppress both operational overvoltage and inrush current, as the optimal combination of VCB switching‐on and switching‐off phases considering the balance between overvoltage and inrush current is achieved based on the particle swarm algorithm.

Choice of the Parameters of an EMI Monitoring System for an AC Traction Network

The problem of ensuring the electromagnetic compatibility of the traction network with railway signaling lines is of practical interest, since electromagnetic interference from the traction network can cause malfunctions in the signaling systems. In order to ensure the electromagnetic compatibility of traction current with track circuits, which are widely used as track vacancy sensors in front of a moving train, electromagnetic interference in rails is periodically monitored in accordance with their maintenance schedule, which makes it possible to detect excessive increases in the level of interference in the rails in a timely manner and prevent possible failures in signaling systems. The problem of developing embedded systems for continuous monitoring of harmonics in the traction network lies in the need to ensure the necessary measurement accuracy of the interference monitoring system for a traction network in accordance with the strict requirements of standards. The correct choice of control system parameters is difficult because the traction current is a non-stationary random process, and the alternating traction current, in addition, has a large dynamic range of harmonic values, their proximity to each other and to a powerful fundamental harmonic, as well as the limitations inherent in the discrete Fourier transform, associated with the impossibility of simultaneously improving the accuracy of measurements in the time and frequency domains, which leads to the need for compromises when choosing the parameters of the monitoring system. The work is devoted to the practice of applying the theory of analog-to-digital conversion and the windowed Fourier transform to develop a technique for correctly choosing the parameters of an electromagnetic interference monitoring system for traction lines.

Development of a Gilbert-type delta in the kame environment: An example from NE Poland

Pleistocene kame deltas are known mainly from glaciomarginal environments, whereas there are fewer examples of deltas where kames formed within decaying ice sheets. In this article, we describe deposits of a Gilbert-type delta formed inside a glacial system. The delta succession was identified in the upper part of the hill, a glacial landform developed within the southern sector of the Scandinavian ice sheet in NE Poland during the Warthian glaciation. The landform is interpreted as a kame, the sediments of which were accumulated in an elongated ice crevasse oriented perpendicularly to the front of the ice sheet. The kame was formed in several stages. In the main stage of development, the crevasse was filled with a lake into which the delta prograded. The lake subsequently underwent a few phases of shallowing, and even an episode of complete drainage.The main delta unit was identified in the outcrop. It is composed of a delta slope and prodelta sediments. A partly preserved older deltaic unit of the initial phase of delta sedimentation also was found. The steep (22–42°) slope of the delta is dominated by gravel and sand. The gravels were deposited from high-energy grain flows and grain falls. Sands were deposited mainly from traction currents during periods when the delta-supplying system was less active. Aggradation of the prodelta was mainly due to sand deposition from traction underflows. Deposition from turbidity currents occurred sporadically there. We explain this unusual situation by the fact that the gravelly sediments feeding the delta slope were relatively well-sorted and contained only small admixtures of fine sand and silt. The sediment sorting process took place in a system of englacial or supraglacial conduits, where the gravels were depleted of fine-grained particles. The development of the Gilbert-type delta was possible because the glacial lake, at least 6–8 m deep, periodically maintained a relatively constant water level, which allowed the delta to prograde. This process required the existence of a steady outflow of water from the lake, which was then an open hydrological system. In the final stage of kame formation, when the lake was completely drained, gravel accumulated from shallow sheet flows.

Multiobjective Optimization of Traction Substation Converter Characteristic and Train Timetable in Subway Systems

Currently, power supply accidents and excessive energy consumption occur frequently in DC traction power systems of multitrain subway lines. Rail potential (RP) exceeds the standard limit frequently, energy consumption and fluctuation of the traction current are high, which are directly affected by the traction substation converter characteristic and train timetable. In this paper, multi-objective optimization of traction substation converter characteristic and train timetable is conducted to realize the safe and economic operation of subway systems. Firstly, a power flow calculation platform with multitrain running dynamically is established to work out the operating parameters of the system. Then, a multi-objective optimization model consisting of maximum RP, energy consumption and maximum traction current is designed. For the coordination of multiple goals to be optimized, an enhanced Non-Dominated Sorting Genetic Algorithm-III (NSGA-III) is proposed to obtain an optimal traction substation converter characteristic and train timetable. Finally, the multi-objective optimization is conducted with the data of Guangzhou Metro Line 2. Results indicate that three optimized objectives are dropped by 43.8%, 33.4% and 40.3% respectively based on the proposed optimization method, which will greatly enhance the energy conservation and power supply safety of subway systems.

Sedimentary architecture of shallow-water fan-delta front in a lacustrine basin: Sangyuan section of Lower Cretaceous Xiguayuan Formation, Luanping Basin, northeast China

The sedimentary architecture of fan deltas, which commonly constitute reservoirs, is a primary control on distribution and recovery efficiency of oil and gas. Deep-water fan deltas have been extensively discussed in the literature, whereas the sedimentary architecture of shallow-water fan-delta fronts, especially the characterization of mouth bar, quantification of architectural elements, and factors controlling the various architectural elements, remain poorly understood. Here, based on the integration of field survey and unmanned aerial vehicle (UAV) observation, the sedimentary architecture of Sangyuan section of the Lower Cretaceous Xiguayuan Formation in the Luanping Basin to is qualitatively and quantitatively characterized. Furthermore, factors controlling the architecture of the shallow-water fan-delta front are highlighted. Five facies associations, which differ in both lithofacies and dimensions, were interpreted in gravel-sand deposits of Sangyuan section, and indicate variations in flow conditions during deposition. The width/thickness ratio of facies associations generally increases rapidly as the flow energy and flow concentration decreases from debris flow to traction currents during the evolution of shallow-water fan delta. Both distributary channels and mouth bars dominate facies associations in the shallow-water fan-delta front, accounting for 53.42% and 36.88% of gravel-sand deposits respectively in Sangyuan section. Mouth bar consists of gravel accretions and sand accretions. Grain size of sediments influences the relative strength of the inertial force and bed friction, which determine the effluent behavior in a river-mouth system and the vertical grain-size trend of mouth bar accretions. Gravel accretions are characterized by normal grading, and these are interpreted as the products of inertia-dominated effluent. Sand accretions exhibit coarsening-upward trends in the river-mouth systems where friction-dominated outflow occurred. The overall vertical grain-size trend of mouth bar depends on the stacking pattern of accretions rather than the grading of one accretion.

SEDIMENTARY ENVIRONMENT AND REDOX CONDITIONS OF THE LOWER TRIASSIC OSAWA FORMATION IN THE SOUTHERN KITAKAMI TERRANE, JAPAN: INSIGHTS INTO OCEAN REDOX STRATIFICATION AND FAUNAL RECOVERY

ABSTRACT The sedimentary environments and redox conditions of the Lower Triassic Osawa Formation in the Southern Kitakami Terrane were reconstructed based on lithofacies, trace fossils, and other paleontological content. The muddy and sandy lithofacies of the Osawa Formation lack evidence of storm waves despite the presence of storm-induced turbidites, suggesting that the oldest deposits of the Osawa Formation were deposited in the proximal part of the outer shelf. In turn, water depth increased from the lower to upper part of the formation, ultimately recording the distal part of the outer shelf. In addition to sandy lithofacies caused by turbidity and traction currents, multiple sandy layers within the muddy lithofacies would have originated via supply into the prodelta setting from a fan delta system. Collapses of the delta front or river system floods could have generated hyperpycnal flows, resulting in abundant supplies of mud and organic matter. Trace fossil analyses revealed that the degree of bioturbation (ichnofabric indices) dramatically decreased as water-depth increased, indicating a steep oxic-dysoxic gradient along the onshore-offshore transect. Diagenetic pyrite framboids indicative of dysoxic/anoxic benthic conditions are abundant at greater water depths. Abundant pyrite framboids less than 6 μm in diameter suggest intermittent euxinicity. With an increase in global weathering, abundant sediment supply including organic matter from the fan delta system could have contributed to the development of ocean redox stratification, which appears to have impacted on the adaptation of both nektic and benthic animals of this area during the Early Triassic.

Energy Efficiency Improvement with Reversible Substations for Electrified Transportation Systems

More and more often overall energy efficiency of an electrified transportation system appears as target of new constructions, sometimes with incomplete definitions of performance indexes to assess that target has been reached. A worked out example is based on the introduction of reversible substations. Reversible substations are a method to improve energy efficiency, whose application in an existing system can be progressive and does not require large traffic intensity to be effective. Their effectiveness depends on some system parameters (nominal catenary voltage in particular). A simulation model fed with experimental data from a line section of Metro de Madrid is used to demonstrate the operation and optimization of reversible substations. Background The ambitious reduction of CO2 greenhouse gas emission within 2050 declared by the European Commission also involves transportation systems. In this context an optimum recovery of the electric braking energy produced by railway vehicles is more and more relevant. Several strategies to completely recover the braking energy are being developed and applied. A methodology that allows the accurate determination of the amount of recovered energy in real operating conditions becomes then a valuable tool. Objective Reversible substations are one of the braking energy recovery methods that are widely applicable. Their effect is analyzed in a system perspective, considering them integrated in the transportation system with its dynamics and various operating points. The effectiveness and consequences of the operation of one or more reversible substations are evaluated by identifying relevant system conditions and scenarios. Methods An electric network model is provided, fed by measured timetable and traction current. Simulation results are analyzed and compared with some experimental results: simulation configurations will be selected to match those of the available experimental data. Results The selected substation no-load output voltage level has a significant effect on efficiency and performance of reversible substations. A reduction of 50 V, from 1700 V to 1650 V produces a decrease of the energy dissipated by the braking rheostat on-board trains of about 13%. The voltage increase caused during braking phases is kept under control better for track positions close to reversible substations: tests show that line voltage increase is 2.5% of nominal value with a reversible substation, and only 0.5% when it is operated. Trimming the thresholds that trigger the operation of the on-board braking chopper (intermingling regenerative and dissipative braking) has a dramatic effect on regenerability: a reduction of 50 V causes an improvement of 19%. Conclusion The paper presents a methodology that merges measurements and circuital model to investigate on the energy saving provided by reversible substations supplying railway system. The methodology has been applied to a real case. Preliminary results regarding the impact of supply voltage level, reversible module position and threshold levels of the braking chopper control system on the dissipated braking energy and power quality has been carried out.

Research on Harmonic Detection Algorithm Based on apFFT

With the improvement of train speed of high-speed railway, the traction power and traction current are increasing. In order to evaluate the influence of traction current harmonic and inter-harmonic on train signal system, accurate detection of harmonic and inter-harmonic is urgently needed. This paper proposed an algorithm based on the all-phase fast Fourier transform method (apFFT) to realize accurate detection of harmonic and inter-harmonic. Firstly, the harmonic and inter-harmonic steady-state model are constructed, and the continuous and discrete time characteristics of the signal are analysed. Secondly, on the basis of theoretical analysis, the apFFT method has the characteristics of high amplitude accuracy and phase invariance by comparing with the traditional FFT method. Finally, the detection results of harmonic signal and inter-harmonic signal show that the apFFT method is significantly improved in frequency accuracy, amplitude accuracy and phase accuracy comparing with other FFT algorithms.

Electrical characteristics of new three-phase traction power supply system for rail transit

A novel three-phase traction power supply system is proposed to eliminate the adverse effects caused by electric phase separation in catenary and accomplish a unifying manner of traction power supply for rail transit. With the application of two-stage three-phase continuous power supply structure, the electrical characteristics exhibit new features differing from the existing traction system. In this work, the principle for voltage levels determining two-stage network is dissected in accordance with the requirements of traction network and electric locomotive. The equivalent model of three-phase traction system is built for deducing the formula of current distribution and voltage losses. Based on the chain network model of the traction network, a simulation model is established to analyze the electrical characteristics such as traction current distribution, voltage losses, system equivalent impedance, voltage distribution, voltage unbalance and regenerative energy utilization. In a few words, quite a lot traction current of about 99% is undertaken by long-section cable network. The proportion of system voltage losses is small attributed to the two-stage three-phase power supply structure, and the voltage unbalance caused by impedance asymmetry of traction network is less than 1‰. In addition, the utilization rate of regenerative energy for locomotive achieves a significant promotion of over 97%.

Evaluating the sedimentological and diagenetic impacts on terrestrial lacustrine fan delta sandy conglomerates reservoir quality: Insights from the Triassic Baikouquan Formation in the Mahu sag, Junggar Basin, Western China

The terrestrial lacustrine fan delta conglomerate reservoirs in the Triassic Baikouquan Formation (BF) are the primary hydrocarbon exploration targets in the Mahu sag, Junggar Basin, Western China. However, the varying lithofacies and complex diagenesis controlling the reservoir quality remain poorly understood. For the sake of revealing how reservoir quality is associated with sedimentary processes and diagenetic alterations, we used integrated approaches like petrographical analysis, cores description, wireline, X-ray diffraction (XRD), scanning electron microscopy (SEM), mercury intrusion capillary pressure (MICP) and measured petrophysical properties. The results showed that sedimentary processes have considerable control over facies distribution, grain size, and clay content, causing spatial variation of reservoir quality within the fan delta deposits. The coarser grain and high clay content fraction at the base of gravity flow will first settle in the fan delta plain near provenance, whereas the finer grains at the top of flows progressively deposit in the fan delta front areas. From proximal to distal fan delta, a progressive conversion from cohesive muddy debris flow into traction current can be inferred from the variations of lithofacies associations. A total of 8 types of microfacies were identified where the conglomerates of the BF were deposited. The grayish-green fine-grained conglomerates concentrated in the subaqueous distributary channels provide the best reservoir performance, whereas debris flow deposits dominated primarily by muddy debrites occupy the worst reservoir quality because of their highest clay content and coarsest grain size.The dominant diagenetic events include mechanical compaction that continued throughout the entire burial, two phases of quartz cementation, dissolution of unstable components, early and late carbonate cementation, precipitation of authigenic clay minerals, and two phases of hydrocarbon charging. It is unveiled that compaction is the predominant mechanism negatively affecting reservoir quality in the fan delta complex, while the effect of cementation on pore reduction of the conglomerate reservoir is weaker than compaction. Simultaneously, a complex relationship exists between reservoir petrophysical properties within different clay minerals. Dissolution does not significantly improve the permeability of the reservoir because of the partial dissolution which primarily generated intragranular pores with strong heterogeneity and poor connectivity. The most favorable reservoirs occur primarily in the subaqueous distributary channels in the fan delta front, which comprise well-sorted fine-grained conglomerates with well-developed residual intergranular pores and secondary dissolution pores and have undergone two phases of oil charge. This work may provide a useful reference for hydrocarbon exploration of the fan delta systems and regions which have encountered similar sedimentary and diagenetic processes.

Оценивание электромагнитной обстановки для аппаратуры автоматики и телемеханики на электрифицированных участках железных дорог

Unstable operation of rail chain equipment and locomotive equipment of automatic locomotive signaling causes false switching of traffic lights that negatively affects the capacity of railway sections and train traffic safety. Such failures in automatic locomotive signaling operation impacts negatively on locomotive crew mentality. At increased intensity of the failures, it is allowed to turn off automatic locomotive signaling equipment as faulty one that significantly worsens train traffic safety. On electrified railways, the main cause of failures in this equipment operation is the interfering effect of traction currents.
 Traction current most strongly interferes with the operation of these devices at this current inequality in rail lines at those places where rail chain equipment is connected or under receiving locomotive coils of automatic locomotive signaling. The interfering activity occurs while an asymmetry (difference in values) of longitudinal and/or transverse resistances of a rail line due to the deterioration of the state of rail butt connectors, throttle jumpers and/or the breakdown of spark arresters in the circuits of connection to rails of grounding circuits of various structures. It is difficult to control the state of electrically conductive elements in rail lines because of their multiplicity and also as their electrical resistance in a tolerance area has milliohm order. It causes the necessity to work out better ways on electro-magnetic situation check and approaches to define the condition of indicated elements such as numerous grounding circuits. It’s time-consuming task but must be carried out with the fulfillment of all requirements for operation in high-voltage lines. This article presents some results on the development of methods for controlling electrically conductive and insulating elements in rail chains and that are more suitable for performing maintenance work of equipment of rail chain and locomotive automatic signaling.

Analysis of Traction Reflux Characteristics of EMU and Improvement of Its Protective Grounding System

The traction reflux characteristics of an electric multiple unit (EMU) are directly related to its safe operation. It is of great engineering value to improve the reflux characteristics by improving the protective grounding system. The typical Chinese EMU with the eight-car power distribution marshaling and decentralized grounding model is taken as the research object of this study, and the circuit model of the traction reflux system is established by Multisim software, the effectiveness of which is verified by field tests. Combining the simulation and measured data, the distribution law of the traction current is analyzed. Based on the advantages of different grounding modes, three improvement schemes of the protective grounding system are proposed. The results show the following: 1) the circuit model of the traction reflux system is effective; 2) the traction current is mainly discharged from the end cars to the railway track; 3) the improvement schemes of the protective grounding system under the normal operation can also improve the traction reflux characteristics under the power loss condition; and 4) based on the proposed protective grounding improvement schemes, on the condition that the car body potential meets the standard requirements, the maximum grounding current amplitude is reduced to 48.4% of the original value, the circulating current is eliminated, the maximum current difference between the two axles of the same coach is reduced to 5.2% of the original value, and the effectiveness of the improvement schemes is verified by field tests.

Transition resistance influence of the upper structure track ballast on the rail-to-earth potential at AC railway sections

Introduction. The purpose of the research is to evaluate transition resistance modifications of the upper structure track in passing from the ballast to the ballastless track. These modifications effect the rail-to-earth potential difference. Moreover, they refer to the reverse traction system, to the reverse traction current of railway automation devices and to the required level of electrical safety guarantee.Materials and methods. The authors used both the analytical method of the rail-to-earth potential testing and the practical one based on experimental studies of the rail track transition resistance measurements. The authors carried out experiments on the Rozengartovka — Boitsovo — Bikin section of the Far Eastern Railway. This section includes the heavy freight traffic with the increased electric resistance of the track ballast by the upper structure redevelopment.Results. The research defines the main criteria of the rail-to-earth potential considering the 2×25 and 25 kV reverse traction of monophase AC systems with the 50 Hz frequency and depending on the experimental area location in terms of traction substations, on the climate and geological factors and on the freight traffic density.Discussion and conclusion. The obtained results will improve the accuracy of the rail-to-earth potential difference considering not only indicated factors, but also the upper structure type, track features and a feed line scheme for contact wire.

Estimation of electrical energy losses in a DC traction rail network during heavy traffic

The growth of traction current leads to losses of electrical energy in the traction rail network, which entails losses for railway companies, including the Russian Railways holding. Additional losses arise due to the deterioration of the resistance of the elements, which occurs in a shorter time in terms of sections on which the movement of trains of increased mass and length is not carried out. Equations for estimation of the power and electrical energy losses in the DC traction rail network have been obtained. These equations are applicable both for the calculation at the sections of the circulation of freight trains, the mass of which does not exceed the weight norm established by the schedule on the route of this train, and taking into account the correction for the passage of long and heavy trains. A simulation model that makes it possible to assess the power losses in a section of a traction rail network depending on changes in the resistance of both individual elements and entire groups that make up the traction rail network, as well as to analyze the effect of the transition resistance rail-ground on the magnitude of leakage currents has been prepared. The need to constantly maintain the elements of the traction rail network in a working condition is determined. It is explained by a significant increase in losses in electrical energy when passing trains of increased weight and length, even with minor deviations of the resistance values from those established by the regulatory documentation. To maintain an operable state and reduce the likelihood of the appearance of faulty elements of the traction rail network, entailing the loss of electrical energy, it is proposed to develop automated monitoring systems for the traction rail network, which ensure the adoption of decisions on the need for maintenance or repair of an element of the traction rail network and transmit information about this repair personnel on duty.

ABOUT THE UP-DATING OF THE REACTOR OF РОБС-1У TYPE PARAMETERS IN THE PROCESS OF THE ELABORATION OF THE REGULATING TABLE OF THE AUDIO FREQUENCY TRACK CIRCUITS

Aim of the given study is the up-dating of the parameters of the reactor of РОБС-1У Type (Single Phase Armoured Dry Type Reactor) during the elaboration of the regulating table of the audio frequency track circuits (ATC). Audio frequency track circuits are supplied from the track circuit transformer of ПОБС -2A (TSPAD) type. Reactor SPADR-1У is used as a restrainer. The analysis of the reasons, influencing the electromagnetic parameters of the reactor of a new model, manufactured in Ukraine is carried out, testing measurements are performed, reactor parameters are recalculated, calculations of the audio frequency track circuits are made, using the updated reactor parameters. Technique. Measurements of the parameters are performed by means of teslameter. The survey of the market of the cold-rolled transformer steel GO is realized. Results. Calculations of the values of the input resistances on the terminals of the track line are carried out, complex value of the reactive resistance of the oscillating contour of SPADR-1У and capacitor Сх of the supply circuit of the audio frequency track circuits which were used for the correction of the calculations of the regulating table of ATC of the railway automation systems is recalculated. It is specified that the incorrect operation of the units of the railway automation of signaling, centralization and blocking (SCB) systems may occur as a result of the impact of the traction current on the track circuits, which use SPAGR-1У of the domestic production. Scientific novelty. Scientific novelty lies in the improvement and correction the coefficients of the formulas for ATC parameters calculation, that enabled to determine more accurately the values in the regulating table of the running line and improve the ATC operation on the used section. Relative errors of the calculations as compared with the seasonal measurements of the parameters, used at the given section did not exceed 3 – 4 % for the currents and voltage. Practical value. Recommendations, regarding the introduction of the updated coefficients in ATC calculations, where the circuit solutions with the reactors of SPADR-1У type are used, have been developed.