Control and protection of superconducting power transmission lines

The paper deals with the analysis of transient processes in a superconducting cable under current overloads and the possibility of stabilizing the superconducting state of the line by means of an automatic control system. The urgency of employing an automatic control system for the recovery and retaining of superconductivity in after-fault conditions is due to the necessity to increase cable stability under the growing level of short-circuit currents in the developing power systems and to reduce the capital costs of the current-carrying system and special current-limiting devices. The paper defines the operating conditions of a system of special protection and control with regard to the specifics of superconducting materials, and gives the required relations to build such systems. Basing on mathematical methods a scheme was developed for analog simulation of the modes of a superconducting cable and for an automatic control system with a proportional regulator which uses the valve of thermal energy released in the cable during current overload as the determining parameter. The results of a comparative analysis of transient processes in a cable with and without a regulator show the advantage of the automatic control system in retaining the superconductivity of a power line in after-fault conditions.