Increased Impedance of Wound HTS Power Cables by Quenching at a Shielding Layer for Fault Current Limiting Function

Abstract

The use of high temperature superconducting (HTS) power cables is viable solution to address the growing demand for electric power, while ensuring low loss and high electric power transmission. Usually, HTS power cables and circular connection of substations reduce grid impedance, and the fault current is increased over the capacity of the circuit breaker. To protect the electric power grid, the fault current should be reduced below the allowable level. Of late, research on HTS power cables having fault current limiting (FCL) functions has increased. An inductive FCL HTS power cable uses the increased inductive impedance caused by magnetic flux leakage to a neighboring iron yoke when a quench occurs at the shielding layer of the cable core due to electromagnetic coupling with the conducting layer. Therefore, there is less heat generation, and the temperature rise is suppressed. In this study, we describe the increased inductive impedance and reduced fault current using a FCL model coil. To demonstrate the electromagnetic coupling between the conducting and shielding layers of the cable core, two concentrically wound REBCO coils were fabricated. The iron yoke inside the coil increases the inductive impedance when a fault current flows through the conducting layer, and quench occurs at the shielding layer. The results are used to develop an FCL HTS power cable with 154 kV, 600 MVA class.