Effect of dielectric layer on the thermal recovery interval of high temperature superconducting power cables

Abstract High Temperature Superconducting (HTS) power cables can play a significant role in upgrading the present commercial electric grids in terms of efficiency and capacity to satisfy the needs of the future. Even though fault current studies on these cables have been conducted to prove their technology readiness, dedicated studies on the thermal recovery performance of HTS cables are limited. A detailed review of the literature on the effects of fault on AC Cold Dielectric (CD) HTS power cables was conducted, with special attention to the recovery phase. It was found that the low thermal performance of the dielectric layer of the cable causes long Thermal Recovery Interval (TRI) and cooldown/warmup time in cables of sufficient length. The main objective of this study is to empirically analyze the effect of the number of PPLP TM layers used in the dielectric layer of CD HTS power cables on their TRI. Moreover, the effects of the initial equilibrium state and the number of PPLP TM layers on the fault current characteristics were also studied. A detailed description of the experimental setup used and the challenges faced during the experimental evaluation of TRI using a model cable in an open bath were presented. An exponential increase in TRI was observed with the number of PPLP TM layers in the dielectric layer. Besides, results show an enhancement in the fault characteristics pointing to the role of the dielectric layer in driving the severity of fault in HTS cables.