The development of the power industry has promoted the production and application of transformers. The level and accuracy of transformers have also been greatly improved. There are more and more types of transformers, such as voltage and current composite transformers, DC current transformers, etc. More and more. However, in the power industry, the transformer used must be consistent with the use of the power system, and the corresponding voltage level and accuracy of the transformer must be developed for the measurement, protection and control of the power system.

With the development of technology and the application of new materials, there are more and more types of transformers, and their performance is getting better and better. Among them, the core type current transformer adapts to the development needs of power construction with various structures of dry type, oil immersion type and gas insulation type. However, with the continuous growth of power transmission capacity, the continuous improvement of power grid voltage level and the continuous improvement of protection requirements, the general iron core current transformer structure has gradually exposed its incompatibility. Its inherent large volume, magnetic saturation, ferromagnetic resonance, small dynamic range and many other shortcomings cannot meet the needs of the new generation of power system automation and power digital network, therefore, we must continue to promote the development of the industry.