Intermittent Current Unsymmetry in an Electric Grid and Its Assessment for Busbars of Traction Substations

Abstract

Violations of regulatory requirements for the quality of electrical energy are regularly exhibited in Russian high-voltage electric grids. This leads to particularly negative consequences in areas with electrified ac railways, which are a powerful source of distortions, including the emergence of current unsymmetry. This paper describes the process and the causes of intermittent current unsymmetry as a conductive disturbance generated by the traction substations. Characteristics are proposed for the evaluation of this unsymmetry. An analytical expression is derived for determining the angle between the symmetrical components of the currents in the busbars of the traction substation. It is shown how the change in the electrical load of the traction grid affects this angle. By the example of a single traction substation model, the correctness of the proposed analytical expression is confirmed, taking into account the used assumptions.