Current Transformer (CT for short) is a device used to measure and convert high current to low current. It is commonly used in power systems and electrical equipment to measure high currents without placing excessive load on measuring instruments and control equipment.

The working principle of the current transformer is based on the principle of Faraday's electromagnetic induction, using the changing magnetic flux of the coil to realize the measurement of the current. A current transformer consists of a primary winding and a secondary winding. The primary winding is wound on a high current wire, while the secondary winding is connected to a measuring device or a relay.

When a high current passes through the primary winding, the resulting changing magnetic field causes electromagnetic induction in the secondary winding, thereby generating secondary current. Due to the winding ratio between the primary and secondary windings, the value of the secondary current is an exact reduction of the primary current. Typically, the secondary current of a current transformer is hundreds or thousands of times smaller than the primary current.

The main functions of current transformers are:

Current Measurement: Converts high currents to low currents suitable for reading by measuring equipment, allowing currents to be easily monitored and recorded.

Protection: In power systems, current transformers are widely used in protective devices such as circuit breakers and relays. They can detect current anomalies, such as short circuits or overcurrents, and trigger protection systems to act accordingly.

Flow calculations: In power systems, current transformers are also used to calculate energy consumption and electricity flow.

Linkage control: Current transformers can also be used to realize automatic linkage control, such as during the starting and stopping of electrical equipment or motors.

Due to the importance of current transformers in power systems, their accuracy and reliability are very important. Therefore, when installing and using current transformers, it is necessary to follow relevant standards and specifications, and perform regular calibration and maintenance.