What is CT Current Transformers

CT Current Transformer  is a type of instrument transformer used in electrical power systems to measure and monitor electric currents. CTs are essential components in power systems for various applications, including protection, metering, and control.

The primary function of a CT is to step down the high current flowing in a power system to a safe and measurable level suitable for instruments, meters, relays, or other devices. The current flowing through the primary circuit, such as a power transmission line, passes through the primary winding of the CT. The secondary winding of the CT is connected to measuring or protective devices, which are designed to handle the lower current levels produced by the CT.

CTs operate based on the principle of electromagnetic induction. When an alternating current flows through the primary winding of the CT, it generates a proportional magnetic field. This magnetic field induces a current in the secondary winding of the CT, which is proportional to the primary current but scaled down in magnitude.

The secondary current of a CT is typically standardized to a specific ratio, such as 5:1, 100:5, or 1000:5, which means that for every unit of current passing through the primary winding, a reduced value is produced in the secondary winding according to the specified ratio. This allows instruments or devices connected to the secondary winding to accurately measure or monitor the current in the primary circuit.

CTs are commonly used in conjunction with protective relays to detect faults and abnormal conditions in power systems. They provide current signals to the relays, enabling them to detect overcurrent, short circuits, or other abnormal conditions and initiate appropriate protective actions, such as circuit breaker tripping.

In summary, CTs are electrical devices used to step down high currents in power systems to safe and measurable levels for monitoring, metering, and protection purposes. They play a vital role in ensuring the safety, reliability, and efficient operation of electrical power systems.