Current transformers can be classified into measurement-type and protection-type current transformers. Measurement-type current transformers are mainly used in conjunction with measuring instruments and are employed to measure the current, power, and energy on the lines during normal operation of the lines; while protection-type current transformers are combined with relay devices. When faults such as short circuits or excessive currents occur on the lines, they supply power to the relay devices to cut off the faulty lines, thereby protecting valuable equipment such as generators and transformers on the lines. The better the magnetic conductivity of the transformer core, the smaller the measurement error and the higher the accuracy. When low ampere-turns and small turns ratios are required, cold-rolled silicon steel cannot meet the measurement accuracy, and permalloy iron cores are greatly limited in use due to their lower saturation magnetic induction and high cost. Nanocrystalline alloy transformer cores, with their excellent magnetic properties such as high magnetic permeability and high saturation magnetic induction, are widely used in precision current transformers, zero-sequence current transformers, PFC, medium and high-frequency transformers and other electrical equipment.