Transient stability of fully superconducting damperless generator at system fault and study of methods to suppress fault currents

Abstract

A fully superconducting generator possesses both superconducting armature windings and superconducting field windings. Thus it has great potential merits to increase efficiency and decrease size and weight compared with a partially superconducting generator that has normal armature windings and superconducting field windings. To obtain these merits, the warm and cold dampers should be omitted. However, a fully superconducting and damperless generator (FSDG) has the following problems when it is operated while connected to a power line system: (1) the dynamic stability of the generator operation is deteriorated because the FSDG has no damping elements; and (2) when the power system is subject to a fault, large transient currents and electric torque are induced in the superconducting armature and field windings, which may cause quenching in the windings. As to problem (1), it was shown that the generator could be stabilized in wide range of the operation by controlling the excitation voltage of the field winding in the authors' previous work. In this paper, problem (2) is addressed. The authors investigate methods to suppress the peak values of the transient currents in the armature and field windings and the transient torque by adjusting electric parameters of the generator and introducing superconducting current limiters (the inductance type and the resistance type). Characteristics of these methods are studied by numerical simulation and it is shown that the introduction of the resistance-type current limiter is the most effective. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 118 (1): 15–27, 1997