Operating characteristics of an HVDC multiterminal transmission line under single-pole faulted conditions and high resistance earth return

Abstract

Most bipolar HVDC transmission lines have ground return capability. The use of a ground return allows transmission of almost half the rated power during an outage of one pole. The increased reliability of a bipolar DC line is one of the major advantages of DC transmission. In the transition from bipolar to monopolar operation due to a line or converter fault, the unfaulted pole operates under different system conditions. In this work, the performance of a multiterminal system with high resistance ground return is investigated. The locations, as well as the magnitudes, of grounding resistances are varied and the effects on system operation observed. In addition, the effects of control parameters, such as transformer tap changing and line current flows, are studied. Multiterminal operation subject to high resistance ground returns, in terms of the constant current-voltage limit characteristics, is discussed. Different control methods for the desired converter characteristics are also described.