Thermal protection implementation of the contact overheadline based on bay controllers of electric transport traction substations in the mining industry

The article presents the principle of thermal protection of the contact overheadlineand substantiates the possibility of practical implementation of this principle for rail electric transport in the mining industry. The algorithm for the implementation of modern digital protection of the contact overhead line as one of the functions of the controller is described. A mathematical model of thermal protection is proposed, which follows from the solution of the heat balance equation. The model takes into account the coefficient of the electrical networktopology, as well as the coefficient of consumption of the current-carrying core of the cable, which determines the reduction in the conducting section from contact erosion and the growth of oxide films. Corrections for air flows are introduced when receiving data from an external anemometer, via telemechanics protocol. The mathematical model was tested by writing a real thermal protection program in the C programming language for the bay controller, based on the circuitry of which is the STM32F407IGT6 microcontroller for the microcontroller unit. Verification tests were carried out on a serial bay controller in 2020. The graphs for comparing the calculated and actual values of temperatures, with different flow rates of the current-carrying conductor of the DC cable, are given. To obtain data, telemechanics protocols IEC 60870-104 and Modbus TCP, PLC Segnetics SMH4 were used.

Detection of Density Changes in Soils with Impedance Spectroscopy

Measurement of soil parameters, such as moisture, density and density change, can provide important information for evaluating the stability of earthwork structures and for structural health monitoring. To ensure the stability of flood protection dikes, erosion at the contact zones of different soil zones must be avoided. In this work we propose the use of impedance spectroscopy to measure changes in density and volume caused by contact erosion. Erosion leads generally to a volume decrease in the contact zones between soils with different grain sizes and, consequently, to cavities in the dike structure. For this purpose, a proctor mould was developed for emulating contact erosion and the realisation of impedance measurements. Experimental investigations show a correlation between volume change of the soils in the proctor mould and impedance value. For a volume change of soil in the range of approximately 1.5% to 5.3%, an impedance change arises in the range of 17.2% to 29.8%. With several investigations we proof, that it is possible to detect material transport by impedance spectroscopy.

Electrical contact performance of various electro-deposited graphene reinforced silver-based nanocomposites

Silver and silver(Ag)-graphene(Gr) nanocomposite coatings were prepared via direct current, pulse current and pulse reverse current on copper electrical contacts for evaluating electrical contact performance. The effects of the addition of Gr and current types on microstructure, crystallographic orientation, mechanical properties and electrical contact performance were investigataed via a scanning electron microscope, an X-Ray diffractometer, microhardness test device and an electrical contact test device, respectively. The addition of Gr changed the Ag surface morphology and decreased grain sizes. Moreover, the addition of Gr significantly improved arc erosion resistivity and decreased the average working temperature during the contact test. In addition, pulse current and pulse reverse current provided a significant improvement in microhardness and electrical contact erosion resistance owing to increased embedded graphene amounts in silver layers.

Equilibrum Composition of Thermal Plasma with Copper and Chromium Vapours Admixtures

Thermal plasma of electric arc is widely used in various technological applications: welding, cutting, lamps, spraying, protection of electrical installations, etc. Process efficiency is defined by different parameters that determine arc operation and influence the energy transfer within the medium. All energy exchanges depend on the medium, which is modified by the presence of the arc and more particularly by the appearance of new species from contact erosion. Sintered Cu-Cr composites are widely used as electrical contacts for vacuum circuit breakers. These materials take advantage of the high thermal and electrical conductivity of Cu and of the refractory and oxygen getter properties of reinforcing Cr particles. The aim of this paper is to give results of the calculation of the equilibrium composition of argon and air plasma with various admixtures of Cu and Cr.