Electromagnetic current transformers are the most commonly used measuring equipment in power systems, with mature technology, low cost, and very high accuracy. They are currently the most commonly used measuring equipment. However, electromagnetic current transformers have many limitations: 1. The difficulty of insulation, especially above 500kV, increases the volume, quality, and price of the transformer due to insulation; 2. When the dynamic range is small and the current is high, the CT will experience saturation, which will prevent the secondary protection from correctly identifying the fault phenomenon; 3. The output signal of the transformer needs to be laid with cables to the secondary equipment and converted into digital quantities in the secondary; 4. CT open circuit can generate high voltage, endangering personal and equipment safety; 5. Easy to generate ferromagnetic resonance; 6. A current transformer has high accuracy at the specified operating frequency, but it can adapt to a narrow frequency range, especially when it cannot transmit direct current. In addition, there is excitation current during the operation of the current transformer, so it is an inductive component with the same drawbacks as a shunt