working principle of a current transformer (CT)

 The working principle of a current transformer (CT) is based on Faraday's law of electromagnetic induction. A current transformer is a type of instrument transformer that is used to measure high currents in power systems and convert them into manageable levels for measurement or protection purposes.

Here's a brief explanation of the working principle of a current transformer:

Construction: A current transformer consists of a primary winding, a secondary winding, and a magnetic core. The primary winding is connected in series with the high-current line carrying the load, while the secondary winding is connected to the measuring or protection devices.

Magnetic Induction: When a current flows through the primary winding, it creates a magnetic field around the conductor according to Ampere's circuital law. The magnetic core, usually made of laminated iron or ferrite material, is placed around the primary winding. The core helps in concentrating and guiding the magnetic field.

Induced Current: The magnetic field generated by the primary current induces a proportional current in the secondary winding through the process of electromagnetic induction. The number of turns in the secondary winding is much higher than the primary winding, which results in a reduced current in the secondary circuit compared to the primary circuit.

Ratio: The turns ratio between the primary and secondary winding determines the transformation ratio of the current transformer. For example, if the turns ratio is 1:100, then a primary current of 100 Amps will result in a secondary current of 1 Amp.

Isolation and Protection: The secondary winding of the current transformer provides electrical isolation between the high-current primary circuit and the measurement or protection devices. It allows safe and accurate measurement of the primary current without directly connecting the devices to the high-voltage circuit. Additionally, the secondary winding's lower current levels are suitable for measurement by ammeters or for providing inputs to protective relays.