Вибір системи живлення низьковольтних однофазних електроприймачів повітряних ліній напругою 220/380 В

Abstract

Two-phase three-wire and single-phase two-wire branches from main three-phase lines are integral components of three-phase four-wire systems. Therefore, the aim of this work is to choose the optimal power supply system for single-phase electri-cal receivers depending on their power and branch length. The comparison of single-, two- and three-phase power supply systems of single-phase electric receivers is carried out and analytical expressions are obtained to determine power losses, phase voltage loss and wire cross section for allowable voltage loss at the same total active load power and its equal distribu-tion between phases. Based on the obtained expressions, the total power losses, voltage loss in phase and neutral wires for different power supply systems are analyzed. In the transition from a three-phase four-wire power supply system of single-phase electric receivers to a single-phase two-wire or two-phase three-wire system with the same total load power and equal load phases with wire cross sections selected for allowable voltage loss, power loss and phase voltage with a corresponding decrease in their active resistance. It is shown that in some cases the use of single-phase and two-phase branches saves conductive materials in comparison with the three-phase linear branch, the cross section of which is inflated due to the need to ensure the condition of mechanical strength. The dependences of the limiting length of three-phase and single-phase overhead insulated lines, which corresponds to the allowable voltage loss, on the active load power are calculated. It is shown that the limiting length of three-phase linear branches significantly exceeds the limiting lengths of single-phase and two-phase branches at the same load power. The optimal version of the power supply system should be selected on the basis of technical and eco-nomic calculation depending on the load capacity, line length and allowable voltage loss.