A current transformer (CT) is a type of transformer that is used to measure alternating current (AC). It produces a current in its
secondary which is proportional to the current in its primary.

Current transformers, along with voltage or potential transformers, are instrument transformers. Instrument transformers scale the
large values of voltage or current to small, standardized values that are easy to handle for measuring instruments and protective
relays. The instrument transformers isolate measurement or protection circuits from the high voltage of the primary system. A
current transformer provides a secondary current that is accurately proportional to the current flowing in its primary. The
current transformer presents a negligible load to the primary circuit.