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Experimental Investigation of a High Temperature Superconducting Pancake Consisted of the REBCO Composite Cable for Superconducting Magnetic Energy Storage System

High temperature superconducting magnetic energy storage system (HT SMES) can be utilized to compensate voltage sag caused by grid-connected renewable energy power generation and can address power fluctuation while the fault occurs in electric power system, which effectively improves stability of power grid and quality of power supply. With the recent increased capacity requirements of SMES, improving the ampacity becomes a core for its application in renewable power grids. Therefore, a novel 100 m high temperature superconducting twisted stacked-tape in tube (TSTT) composite cable with inner spiral cooling channel is proposed and is manufactured for constructing a 3 MJ toroidal SMES in China Electric Power Research Institute. A prototype pancake using this 100 m TSTT cable is constructed. An experimental set up and critical properties measurement systems are built including a 3000 A dc current power supply, a closed-loop cooling system with LN2 and a high-precision data acquisition system of national instruments based on LABVIEW. The characteristics of critical current for the pancake under an operating temperature of 77 K are investigated in this paper. The experimental results have validated the feasibility of this TSTT composite cable for the MJ-class energy storage magnet. It provides a valuable reference to the large-scale HT SMES applied in the power grids based on a high temperature superconducting composite cable technology.