ELECTRICAL EQUIVALENT CIRCUIT MODELING OF SELF-SHIELDING DC HIGH TEMPERATURE SUPERCONDUCTING CABLE CONSIDERING THE EFFECT OF FAULT ON ITS ELECTROTHERMAL PERFORMANCE

Abstract

DC High temperature superconducting (HTS) cables have been considered from the point of view of very low losses and high current capacity. In order to properly utilize these cables in power systems, it is necessary to evaluate their electrothermal and magnetic performance in steady and transient conditions as well as in different power network structures. In this paper, a 1 kV 3 kA self-shielding DC HTS cable with a multilayer structure is modeled using the electrical equivalent circuit method (ECM) in MATLAB/SIMULINK. The current flowing through the tapes and layers, temperature and losses, as well as the magnetic field and critical current in different layers, according to the specific conditions of the self-shielding DC HTS cable, were investigated as important parameters in evaluating the steady and transient operation. In order to study the transient state in the power system, pole-to-pole and pole-to-ground faults were simulated for different fault resistances. In addition, the effect of AC ripple on the DC current entering the cable is considered as a factor affecting losses. The results show that under stable operation of power system, the current flowing through the forward and backward layers is equal. However, in transient conditions, the balance of current between the layers will be lost. Also, with the decrease in fault resistance, in addition to the increase in the current flowing through the layers and the imbalance between them, the temperature and losses show a significant increase. In some situations, the fault caused a change in the operating mode of the superconducting cable, which can be dangerous for the operation of the cable