What is The operation of Current Transformer?

CT together with a ammeter is used to measure the current in high current or high voltage circuit, where a normal ammeter can not be connected in series in such high voltage or high current circuits. It is a secondary winding (like in transformer) wound on a single core primary wire and relative secondary current reperesnets the primary current. CT are also used protection purposes. Basic principle of CT i same either for metring or protection.