An Equivalent Scheme for Calculating Short-Circuit Currents in a Traction Power Supply System with Two-Way Power Supply

Abstract

The cause of a methodological error in the calculations of short-circuit currents as exemplified in the power supply of a traction network with two-way supply has been shown. It is to be noted that, in an actual power supply circuit, two adjacent traction substations are connected along the 110 (220)-kV lines by mutual resistance, whereas there is no such connection in the designed arrangement. On the basis of the designed scheme, a new equivalent circuit is formed, in which the resulting traction power circuit remains unchanged. The transformation of the initial circuit has enabled removing the error and calculating the short-circuit voltages in the traction network explicitly. Replacement of a symmetric three-phase external power supply system and a traction transformer with an equivalent single-phase circuit when calculating two-phase short-circuit currents in the traction network is shown to be viable. The validity of replacement of a symmetrical three-phase network for a single-phase one has been proved both by transformation of the three-phase equivalent circuit and by means of the equivalent generator method. It is established that, despite the difference in phase resistances of substations with Y/Δ and Y/Y transformer connection circuits, equations for determination of two-phase short-circuit currents prove to be the same.