Feasibility study of capacitance based quench detection technique for HTS power transmission cables

Abstract

2nd Generation High Temperature Superconducting (2G HTS) tapes are replacing the conventional Low Temperature Superconducting (LTS) wires in various felds of applied superconductivity, especially in the power transmission applications. Transients in the electrical grid can result in the loss of superconductivity leading to thermal runaway. This phenomenon is known as quench. To avoid catastrophic consequences, timely detection of quench is imperative. However, the HTS materials possess a low Normal Zone Propagation Velocity (NZPV) compared to LTS materials during quench. This property combined with a low electromagnetic shielding makes the conventional voltage tap detection technique unreliable for HTS power transmission cables. A capacitance based quench detection technique is proposed and its feasibility is studied. A variation in the permittivity of the cryogenic fuid and the dielectric can be observed in association with the heat generation during faults. This can be refected as the variation in the measured capacitance between cryostat and cable former. In this study, this capacitance is computed using the FEM model of HTS cable operating at various temperatures along with diferent vapour liquid ratios of cryogen. The results of this work can be extended into experiments for quench detection in HTS power transmission cables.