In the huge and complex power system, each component plays an indispensable role, and they jointly maintain the stable transmission and distribution of electric energy. Among them, the current transformer, as a key measurement and protection device, is inconspicuous but crucial. It is not only the "eyes and ears" of the power monitoring system, but also the "invisible guardian" of the safe operation of the power grid.

A current transformer is a special transformer designed to convert high current (usually large current on the primary side) into low current (small current on the secondary side) proportionally, usually with standard values ​​such as 5A or 1A, for measurement, metering and relay protection. This process is based on the principle of electromagnetic induction. When current flows through the primary conductor, it will generate magnetic flux in the surrounding iron core, and then induce current in the secondary winding. Due to the design of the transformer, the ratio of the primary to secondary current (i.e., the transformation ratio) is constant, and the secondary current is in the same phase as the primary current, which makes the current transformer an ideal tool for accurately measuring large currents.

The role of current transformers
Measurement and metering: In the power generation, transmission, distribution and consumption of the power system, current transformers accurately convert large currents into standard small currents, supplying measuring instruments such as electric meters and power factor meters to achieve accurate monitoring of power consumption and load conditions.
Relay protection: As an important part of the relay protection device, the current transformer can quickly sense abnormal currents in the line (such as short circuits and overloads), and transmit this signal to the relay to trigger protection actions, such as tripping, thereby effectively preventing equipment damage and fire and other safety accidents.
Current monitoring and analysis: In smart grids and energy management systems, the data provided by current transformers is the basis for advanced functions such as power quality analysis, load forecasting, and fault diagnosis, which helps to improve the operating efficiency and reliability of the power system.

With the trend of intelligent and networked power systems, current transformers are also facing the challenge of technological upgrading. Although traditional transformers have been maturely used for many years, they have limitations in high precision, wide-band response, miniaturization, and digitization. Therefore, new types of current transformers such as optical current transformers (OCT) and electronic current transformers have emerged. They use optical fiber sensing technology or digital signal processing technology to achieve higher measurement accuracy, wider dynamic range and stronger anti-interference ability, providing strong support for the development of smart grids.