Superconducting magnets are widely used in NMR spectrometers in order to achieve higher magnetic-field strength and stability. Especially, the magnetic-field stability of low-temperature superconducting (LTS) magnets commonly used is realized using a persistent current mode. Recent progress in high-temperature superconductors (HTS) and magnet technologies is promoting the development of magnets to exceed 1 GHz (23.5 T) limited by the low critical-current density of LTS in a high- magnetic field. However, there is still no superconducting joint for HTS to enable a persistent current mode. We have developed a 1,020 MHz (24.0 T) NMR using a Bi₂Sr₂Ca₂Cu₃O_x (Bi-2223) innermost coil with an external power supply. The driven-mode operation of a large-scale magnet for the high-resolution NMR was a new challenge requiring related problems to be investigated. A highly stabilized power supply and equipment for power outage have been developed for the high-resolution solution NMR and long-term operation.