Моделювання та аналіз електротеплових процесів в установках індукційної термообробки алюмінієвої жили силових кабелів

Introduction. The development of the electric power industry is directly related to the improvement of cable lines. Cable lines meet modern requirements for reliability, they are increasingly used. Problem. Currently, power cables with an aluminum multi-conductor core, which requires heat treatment - an annealing process at the stage of the technological manufacturing process, are widespread. This process makes it possible to desirably reduce the electrical resistance of the wire and increase its flexibility. For effective use of induction heating during annealing of an aluminum core, it is necessary to determine the optimal frequency of the power source of the inductor. Considering the long length of the inductor and the large number of its turns, the numerical calculation of the electromagnetic field, which is necessary for calculating the equivalent electrical parameters of the turns of the inductor and its efficiency, requires significant computer resources. The goal is to develop a computer model for calculating electro-thermal processes in an induction plant for heating (up to the annealing temperature) an aluminum core of a power cable moving in the magnetic field of a long multi-turn inductor, as well as obtaining frequency dependences of the equivalent R, L parameters of such an inductor and determining the optimal the value of the frequency of the power source, which corresponds to the maximum value of the electrical efficiency of the inductor. Methodology. The mathematical model was developed to analyze the coupled electromagnetic and thermal processes occurring in a core moving in a time-harmonic magnetic field of an inductor at a constant speed. The differential equations for the electromagnetic and temperature fields, taking into account the boundary conditions, represent a coupled electro-thermal problem that was solved numerically by the finite element method using the Comsol software package. For a detailed analysis of the electromagnetic processes in the inductor, an additional problem was considered at the level of the elementary cell, which includes one turn of the inductor and a fragment of the core located near this turn. Results. According to the results of the calculation of the electromagnetic field in the area of the elementary cell, the equivalent electrical parameters of one turn of the inductor and the entire multi-turn inductor were calculated depending on the frequency of the electric current. The frequency dependences of the electrical efficiency of the inductor were calculated. Originality. Taking into account the design features of the inductor (its long length and large number of turns), the method of multiscale modeling was used. Electro-thermal processes in the core were studied at the macro level, and the distribution of the electromagnetic field and electric current density in the cross-section of the massive copper turn of the inductor was calculated at the micro level – at the level of an elementary cell containing only one turn of the inductor. The frequency dependences of the equivalent R, L parameters of the inductor, taking into account the skin effect, the proximity effect, and the geometric effect, were obtained, and the quantitative influence of the electric current frequency on these effects was studied. Practical value. The dependence of the electrical efficiency of the inductor on the frequency of the power source was obtained and it was shown that for effective heating of an aluminum core with a diameter of 28 mm, the optimal value of the frequency is in the range of 1–2 kHz, and at the same time the electrical efficiency reaches values of ηind = 0.3–0.33, respectively.У роботі досліджено електромагнітні та теплові процеси в установках індукційного нагрівання алюмінієвої жили силових кабелів та умови реалізації технологій її відпалювання. При математичному моделюванні вказаних процесів ураховано такі конструктивні особливості індуктора, як його значна довжина і відповідно велика кількість його витків, що викликало необхідність використати метод мультимасштабного моделювання. При цьому на макрорівні розраховувались електротеплові процеси в жилі, що рухалась у магнітному полі індуктора, а на мікрорівні (тобто на рівні елементарної комірки, що має лише один виток індуктора) визначався розподіл електромагнітного поля та густини електричного струму в перерізі масивного мідного витка індуктора з урахуванням особливостей його конструкції. На обох рівнях у роботі використовувався чисельний метод скінченних елементів, реалізований в пакеті програм Comsol. За результатами розрахунку електромагнітного поля на рівні елементарної комірки, отримано частотні залежності еквівалентних R, L параметрів індуктора із урахуванням скін-ефекту, ефекту близькості та геометричного ефекту. Досліджено кількісний вплив частоти електричного струму на ці ефекти та отримано залежність електричного ККД індуктора від частоти джерела електроживлення. Показано, що для ефективного нагрівання алюмінієвої жили діаметром 28 мм оптимальне значення частоти знаходиться в діапазоні 1–2 кГц, в якому електричний ККД може досягати значень ηind = 0,3–0,33

Overview of the ways to reduce telemetric information redundancy

The redundancy of telemetric information significantly complicates the real-time processing of the information flows. To speed up the telemetry processing process, the methods for telemetric information redundancy reduction should be applied in order to reduce its flows entering the monitoring systems while maintaining a high speed of processing and reliability of the information. The article provides an overview of the methods for reduction of telemetric information redundancy, such as the increase in PHY-rate of telemetry channel, the Huffman algorithm, the batch mechanism for generation and transmission of telemetry information, the adaptive difference algorithm, the algorithm for transmission of the information based on its representation by residual images, Golomb-Rice codes, reversible compression method. The advantages and disadvantages of each of them are considered. Recommendations on the use of multi-level telemetry information compression system are given, which makes it possible to effectively combine target data compression algorithms that give the highest compression ratio depending on the type of telemetry information transmitted