What does a current transformer (CT) sense?

A current transformer (CT) is specifically designed to measure the amount of electric current flowing through a conductor. It operates by producing a reduced current proportional to the actual current flowing in the circuit, allowing for safe measurement of high currents without direct exposure to the high-voltage lines.

Current transformers work based on electromagnetic induction, which means they generate a secondary current that is directly related to the primary current passing through their core, making them ideal for monitoring and metering applications. This ability to sense and convert high currents into manageable levels is crucial in power systems for protection, measurement, and control.

The other options refer to different types of electrical measurements. Voltage refers to the potential difference between two points, frequency signifies the rate of oscillation or cycles per second of alternating current, and power represents the rate at which electrical energy is transferred or converted. While these are all important electrical parameters, they are measured using different devices, such as voltage transformers for voltage, frequency meters, and power meters, rather than current transformers.