A current transformer (CT) is a device used to measure alternating current (AC) flowing in a conductor. Its primary purpose is to transform high currents in power systems into a proportional lower current suitable for measurement and protection purposes. The CT operates based on the principle of electromagnetic induction, where the primary conductor carrying the current induces a current in a secondary winding wound around a magnetic core. This secondary current is proportional to the primary current but scaled down according to the turns ratio of the transformer.
One of the most common uses for a current transformer is in electrical metering and monitoring applications. In power distribution systems, CTs are placed around the main conductors carrying high currents to provide accurate measurements of current flow. This data is crucial for billing purposes, load monitoring, and power quality analysis.
CTs, along with potential transformers (PTs), are commonly used in conjunction to provide complete measurement capabilities in power systems. While CTs measure current, PTs measure voltage. Together, they enable comprehensive monitoring and protection of electrical equipment and systems.
Transformers in general are used to transfer electrical energy from one circuit to another, typically by means of electromagnetic induction between coils. They are essential in voltage transformation, isolation, and impedance matching in electrical systems.
The term “CT” is not typically referred to as a “step-up transformer.” CTs are designed to step down high currents to a lower level suitable for measurement devices or protective relays. They are not intended for voltage transformation but rather for current measurement and protection applications. The term “step-up transformer” usually refers to a transformer that increases voltage from the primary to the secondary winding, which is fundamentally different from the role and function of a current transformer in electrical systems.