TRANSIENT ANALYSIS IN THREE-PHASE ELECTRICAL CIRCUITS WITH DISTRIBUTED PARAMETERS AND INTERFACIAL CONNECTION ON THE EXAMPLE OF HIGH-VOLTAGE CABLE LINE

Abstract

The analysis of transients in three-phase electric circuits is carried out, which allowed to consider changes of transient components of currents and voltages of each phase of three-phase cable power line and to estimate the level of overvoltage and amplitude of short-circuit currents in screens taking into account transposition. Using the MatLab/Simulink program, software tools and methods for numerical calculation of transient electromagnetic processes in the designed 330 kV cable line were developed to analyze the level of voltages on the screens and currents in the cable cores at different switching modes. The calculations of a specific 330 kV cable line with a length of 13 km, laid for the first time in Ukraine for the power supply of the electric steel complex, were carried out. The calculation of the emerging transient electromagnetic processes in such a line under different conditions of its connection to the three-phase power supply network is carried out. Many types of switching overvoltages are subject to limitation. Feasibility studies of overvoltage protection measures include assessment of statistical characteristics of damage due to damage, simple or extraordinary repair of electrical equipment of the cable line, as well as due to violation of the technological process by consumers. The above determines the relevance of modeling and analysis of electromagnetic processes that occur when connecting and switching cable lines in ultra-high-voltage three-phase electrical circuits. This allows us to recommend the results of work to develop methods for determining the allowable and emergency modes of similar three-phase cable transmission lines and the choice of rational circuit design solutions in their design. Analyzing the transients in the mode of single-phase short circuit, we can conclude that to select the optimal lengths of the transposition sections of cable screens, it is necessary to consider single-phase short circuit mode, as in this mode there are unacceptable overvoltages on cable screens and currents in three-phase cable lines.