Current transformer, as an indispensable and important component in the power system, plays multiple roles such as measurement, protection and control. This seemingly simple electrical device carries the heavy responsibility of ensuring the safe and stable operation of the power system.

Current transformer is a special electrical device that works based on the principle of electromagnetic induction. Its core function is to convert the large current on the primary side into the small current on the secondary side in proportion, so as to facilitate accurate measurement and protection of secondary equipment such as ammeters and relays. This conversion not only reduces the magnitude of the current, but also realizes the isolation of high voltage and large current, thereby improving the safety and accuracy of measurement. Based on Faraday's law of electromagnetic induction, when the primary current passes through the transformer, a magnetic field is generated in its iron core, and then an electromotive force is induced in the secondary winding. This induced electromotive force is proportional to the primary current. By adjusting the turns ratio of the primary and secondary windings, the current can be converted proportionally.

There are various types of current transformers. According to their uses, they can be divided into measuring current transformers and protective current transformers; according to the insulating medium, they can be divided into dry, cast, oil-immersed and gas-insulated current transformers; according to the installation method, they can be divided into through-type, pillar, bushing and busbar current transformers. In addition, there are electromagnetic current transformers and photoelectric current transformers. These different types of current transformers have their own characteristics and are suitable for different application scenarios, meeting the diverse needs of the power system.

In the field of measurement, protection and control of power systems, current transformers play a pivotal role. In power plants, substations and power transmission and distribution systems, current transformers are key equipment for realizing electric energy metering, equipment protection and automatic control. By accurately measuring the current, the current transformer can promptly detect abnormal conditions in the power system, such as overload, short circuit, etc., thereby triggering the action of the protection device, cutting off the faulty part, and protecting the power equipment from damage. In the field of industrial automation, current transformers are also widely used to monitor and control the current of motors, transformers and other equipment to improve energy efficiency and the stability of equipment operation.

The main technical parameters of the current transformer include transformation ratio, accuracy level and rated current. The transformation ratio refers to the ratio of the primary current to the secondary current, the accuracy level reflects the error range of the current transformer when measuring the current, and the rated current refers to the maximum current value allowed to pass through the current transformer under normal working conditions. The current transformer also has performance indicators such as saturation characteristics and dynamic response characteristics, which are of great significance for evaluating its performance.

When installing, using and maintaining the current transformer, it is necessary to select a suitable installation location and method according to its type and purpose, and ensure that the installation is firm and reliable. During use, the appearance and wiring of the current transformer should be checked regularly, its operating temperature and noise should be monitored, and abnormal conditions should be discovered and handled in time. In terms of maintenance, the current transformer should be cleaned and maintained regularly to extend its service life and improve its performance stability.

Current transformers and voltage transformers are often used together in power systems to jointly realize the measurement, protection and monitoring functions of the power system. Both are based on the principle of electromagnetic induction in terms of working principles, but they differ in specific implementation methods and application scenarios. Current transformers are mainly used to measure current, while voltage transformers are mainly used to measure voltage. This combination not only improves the measurement accuracy of the power system, but also enhances its protection and control capabilities.