Recovery time of high temperature superconducting tapes exposed in liquid nitrogen

• A novel method based on a sequence of AC pulses is presented.
• Liquid nitrogen temperature is used as criterion to judge whether the sample has recovered.
• Recovery time of some tape doesn't increase with the amplitude of fault current.
• This phenomenon is caused by boiling heat transfer process of liquid nitrogen.
• This phenomenon can be used in optimizing both the limiting rate and reclosing system.

The recovery time is a crucial parameter to high temperature superconducting tapes, especially in power applications. The cooperation between the reclosing device and the superconducting facilities mostly relies on the recovery time of the superconducting tapes. In this paper, a novel method is presented to measure the recovery time of several different superconducting samples. In this method criterion used to judge whether the sample has recovered is the liquid nitrogen temperature, instead of the critical temperature. An interesting phenomenon is observed during the testing of superconducting samples exposed in the liquid nitrogen. Theoretical explanations of this phenomenon are presented from the aspect of heat transfer. Optimization strategy of recovery characteristics based on this phenomenon is also briefly discussed.