Calculation of aerial contact wire volume heated by a moving electric ARC

The article is devoted to the study of the problem of electrified railways electric locomotive current collectors’ interaction violation with an aerial contact wire, accompanied by the occurrence of an electric arc. Current collection disorders, accompanied by arcing, have a destructive effect on the contacting elements, causing their thermal erosion. Places where current collection violations occur should be registered and diagnosed in a timely manner in order to prevent an emergency situation associated with burnout or breakage of the aerial contact wire. In order to further develop the system of technical diagnostics for current collection disorders accompanied by arcing, it is necessary to study the nature and parameters of the processes occurring during these violations. The main part of the article is devoted to the study of the area of heating the aerial contact wire by a moving electric arc. The characteristics describing the heated area are geometric parameters, including the area in the cross section of the wire and the volume of the area. To obtain the necessary data, the method of heat sources was applied, which is a mathematical model that describes the process of heat propagation in an aerial contact wire. The electric arc arising when the current collector breaks off is considered as a mobile heat source distributed over the aerial contact wire surface in the heating zone and having a limited radius of the heating spot. Based on the heat propagation process peculiarities inside the aerial contact wire, a method for calculating the volume of the heated area bounded by an isothermal surface of a certain temperature is presented. The heated area was visualized using the PTC MathCAD.

The Use of Innovative Contact Strip for Pantographs of Electric Rolling Stock. Experience in Operational and Bench Tests

Modern high-tech composite materials are widely used in various sectors of the economy, in particular, in railway transport. Among the areas of application of such innovative materials, the manufacturing of contact strips for pantographs of electric rolling stock should be mentioned. Innovation is primarily understood as the self-lubricating property of the working surface of the linings. The linings made of such materials differ from the traditional graphite (coal) ones by the increased content of metal additives, in particular copper, which limits the possibility of their use on electric rolling stock in the countries of the European Union. Regulatory restrictions on the content of copper (35% and 40%) are associated with possible damage to the contact wire, in the case of using overlays with a content of copper (metals) greater than these restrictions. On the railways of Ukraine (countries of the former USSR), there are also restrictions on the use of linings of different types according to the degree of wear of the contact wire, no more than 40 microns is allowed per 10 thousand passes of the locomotive pantograph along the contact wire. These standards are verified during operational and bench tests. The aim of the article is to present the types of tests and compare the obtained values with similar indicators in the case of using a traditional contact strip for pantographs of electric rolling stock. The results obtained confirm the possibility of using innovative linings on iron networks, since the wear of the contact wire during testing is much lower than that of the normative and knife than for traditional types of linings. In addition, during a set of tests, the fact of improving the quality of the working surface of the contact wire was established, which positively affects the extension of the service life of the contact wire.

The Influence of Pantograph Carbon–Metal Composite Slider Thermal Properties on the Railroad Wire Temperature

This article presents the methodology, description, and results of experimental studies aimed at determining the impact of the copper concentration in a carbon–metal composite contact strip on the maximum temperature of the copper contact wire during a contact event when used for operation in the railway industry in Europe. Based on these tests, we determined the minimum percentage of copper that is required for the composite to meet the normative requirements for current loads. In addition to experimental research, a 3D FEM numerical model was also developed in which the contact strip and contact wire geometry were mapped, along with imposed loads resulting from the test for current loads mentioned above. Fifteen simulation variants were carried out for the established model, where the value of the thermal conductivity coefficient and the specific heat coefficient were varied. On this basis, we analyzed the sensitivity of thermal coefficients to the contact wire temperature and determined the minimum conductivity coefficient value, which allowed the maximum copper contact wire temperature of 120 °C to be obtained during the verification tests.

Analysis of collision dynamics of lifting the pantograph during vehicle operation

It is a practical engineering problem to lift the pantograph during train operation. In this paper, a pantograph-catenary (PAC) model is established, which can realize pantograph lifting during train operation. In this model, the contact model between contact piece and contact wire is established using the polygon contact model (PCM). The PAC collision test rig is established, and the simulation model at low speed is verified by comparing the contact force and vertical acceleration of contact piece obtained from simulation and test. The factors influencing the process of pantograph lifting are analyzed. The simulation results show that the position where the dropper and contact wire are connected is the most disadvantageous position for pantograph lifting. The maximum impact force increases with the increase of pantograph lifting speed, and the relationship between them is linear. In addition, if the influence of aerodynamic force is not considered, the running speed of vehicle will not affect the pantograph lifting process.

Technology of the Contact Wire Manufacture for High-Speed Railways

The article presents an overview of possible technological schemes to produce an overhead contact wire for railways. Pilot experiments were carried out on the manufacture of a contact wire made of CuMg0.3, CuMg0.4 and CuMg0.5 alloys and having a nominal cross section of 100 mm2. The contact wire was obtained from a continuously cast rod with small section, which was subjected to plastic deformation using the Conform technology and cold drawing of the extruded rod. In the casting process, we encountered the formation of cracks on the cast rod surface and the rods breakage. The inner surface of the graphite bushings of the mold after casting the rod was studied and a thin gray layer was found on the inner surface of the graphite bushings. Areas of the graphite bushing with gray layer were studied by scanning electron microscopy and element-by-element mapping was performed with the selection of a spectrum in the sediment layer area. In order to determine the phase composition of the sediment layer it was analyzed by the method of full-profile analysis of the X-ray diffraction pattern according to Rietveld. X-ray phase analysis showed the CuMg2 and Cu2Mg phases presence. This allowed us to assume a possible mechanism for the formation of the sediment layer. Ultimate tensile strength, elongation and electrical resistivity was determined. Analysis showed that the overhead wires made of CuMg0.3, CuMg0.4, CuMg0.5 alloys meets the requirements of GOST R 55647-2018 for wires made of the second conditional group bronze.

To the Issue of Low-Alloyed Copper Alloys for Contact Wires

This paper is about a comparative analysis of the requirements of the Russian standard, the standard of the European Union and the PRC for overhead contact wires for electrified high-speed railways. New generation contact wires must have a high level of mechanical, electrical and operational properties. The Russian standard does not regulate the chemical composition of alloys used for the contact wires manufacture. Unlike the standards of the European Union and China, the Russian standard regulates the maximum value of the relative creep. Compositions, mechanical properties, electrical resistivity and recrystallization temperature for the contact wires with a cross section of 120 mm2 are given. The requirements for the material for the contact wire are presented. The need to use more durable conductive materials instead of copper is noted since mechanical loads and operating temperatures are constantly increasing. The values of mechanical properties, recrystallization temperature and creep of contact wires made of copper alloys are given. Based on the analysis results of the literature data and the experiments, alloys of the Cu-Mg system are recommended as a material for the contact wire manufacture for an overhead network system for high-speed railways.

Railway overhead contact wire monitoring system by means of FBG sensors

Safety of infrastructures represents one of the most significant concerns for governments and service providers to preserve people's well-being. One of the main ways to keep in safe facilities (buildings, bridges, railways, etc.) involves the use of monitoring sensor systems in charge of measuring critical operating conditions. Those measurements together with periodical maintenance, contribute to minimize potential risks that the infrastructure faces. The paper aims at designing, developing, and testing a monitoring system for mechanical stresses acting on the overhead contact wire (OCW) to ensure the operational safety of the railway network. In this regard, the paper proposes two Fiber Bragg Grating (FBG) sensors-based solutions, relying on the ability of these sensors to allow real-time and continuous data acquisition. The first one consists in a polyimide-coated sensor bonded on an OCW clamp, the second one is a copper-coated sensor hanging between the two separated halves of an OCW clamp. Significant results have been obtained mechanically testing both solutions, trying to simulate the operative conditions.