Electromagnetic Effect of an Alternating Current Traction Power Supply System with a High-Voltage Power Cord on Electrical Installations and Networks of Nontraction Consumers

Russian Electrical Engineering - In this paper, we ground a method for calculating switching overvoltages including the discharge of lightning currents into the contact network and into a...     

Diagnostics of Multioperation Processes Using Basic Cells of Digital Homogeneous Structures

Russian Electrical Engineering - The cells of homogeneous digital structures designed for multioperation process diagnostics are considered in the form of graphic models. Digital circuits and...     

Operational management of trunk main discolouration risk

Despite significant on-going investment, water companies continue to receive an unacceptable number of discolouration related customer contacts. In this paper, data from intensive distribution system turbidity monitoring and cluster analysis of discolouration customer contacts indicate that a significant proportion of these contacts are due to material mobilising from the trunk main system, and operational flow increases are shown to have a higher discolouration risk than burst incidents. A trunk main discolouration incident highlighting this risk is discussed, demonstrating the need for pro-active trunk main risk assessments. To identify the source of the material event flow rates were modelled using the PODDS (prediction of discolouration in distribution systems) discolouration model. Best practice pro-active management is demonstrated in a case study where the PODDS model is used to implement managed incremental flow changes on a main with known discolouration risk with no discolouration impact to customers and significant cost savings.     

Development of method to improve efficiency of residual current device under 1000 V on excavators of mining enterprises

This article presents the results of experimental studies on a coal mine. According to the results, the current of single phase-to-earth fault in the network under 1000 V has a value less than the current of the residual current device set point. This article presents a method aimed to improving the efficiency of the residual current device used on excavators and drill-rings at mining enterprises. Indeed, the method developed to improve the efficiency of residual current devices under 1000 V is based on setting up a direct current into three-phase mains with a fixed set-point of protection against any phase-to-ground insulation damage, where electric equipment is switched off due to increases of capacitance between a conductor and earth when live-line bare-hand touching of electric equipment occurs.     

Intensification of nonlinearity by dispersed events in media with structure and generation of various dominant frequencies in P- and S-waves

A model of a continuum with a structure described by infinite order equations of motion is proposed. In case that a wave is very long as compared with the size of the structure, equations are reduced to the fourth-order equations. A closed equation of motion, including nonlinear, dispersed and wave members, is derived. It is shown that solutions in the form of soliton waves exist only in media where wave velocity grows with pressure. In the media, where soliton waves do not exist, quasi-stationary solutions with multiple frequencies prevail. It is found that the nonlinear effect of multiple frequencies is unexpectedly high even for small deformation as dispersion violently intensifies nonlinear events. Moreover, in the domain of small deformation, there exist solutions for longitudinal and transversal waves with the same length and different frequencies. The solutions for the same length waves with different frequencies most often occur in seismology and seismic explorations.     

The Effects of Annealing After Equal Channel Angular Extrusion (ECAE) on Mechanical and Magnetic Properties of 49Fe-49Co-2V Alloy

Metallurgical and Materials Transactions A - Equal channel angular extrusion (ECAE) of 49Fe-49Co-2V, also known as Hiperco® 50A or Permendur-2V, greatly improves the strength and ductility of...     

High Temperature Oxidation Behavior of Conventional and Nb-Modified MAR-M246 Ni-Based Superalloy

The present investigations focused on the thermal oxidation of two variants of MAR-M246 alloy having the same contents of Ta and Nb in at. pct, considering the effects of total replacement of Ta by Nb. The alloys were produced by investment casting using high purity elements in induction furnace under vacuum atmosphere. The alloys were oxidized pseudo-isothermally at 800 °C, 900 °C and 1000 °C up to 1000 hours under lab air. Protective oxidation products growing on the surface of the oxidized samples were mainly Al₂O₃, Cr₂O₃. Other less protective oxide such as spinels (NiCr₂O₄ and CoCr₂O₄) and TiO₂ were also detected as oxidation products. The conventional alloy exhibited slight internal oxidation at 800 °C and an enhanced resistance at 900 °C and 1000 °C. The Nb-modified alloy presented an exacerbated internal oxidation and nitridation at 900 °C and 1000 °C and an enhanced resistance at 800 °C. At 1000 °C, Nb-modified alloy was particularly affected by excessive spalling as the main damage mechanisms. From a kinetic point of view, both alloys exhibit the same behavior at 800 °C and 900 °C, with k_p values typical of alumina forming alloys (2 × 10⁻¹⁴ to 3.6 × 10⁻¹³ g² cm⁻⁴ s⁻¹). However, Ta modified alloys exhibited superior oxidation resistance at 1000 °C when compared to the Nb modified alloy due to better adherence of the protective oxide scale.

     

Plastic Deformation Resistance of Steel Grades EP450-Sh and EP823-Sh in Hot and Cold State

Metallurgist - The article presents the results of plastometric studies on hot deformation and studies on the hardening curves in cold deformation of EP450-Sh (12H12M1BFR-Sh) and EP823-Sh...     

Power Supply at Metallurgical Iron-and-Steel Works: Features and Development Prospects

Metallurgist - The article provides a brief assessment of the current state of power supply units at metallurgical plants and prospects for their future development. The principal power-supply...