Current transformers (CT)
A current transformer (CT) is a type of instrument transformer designed to
provide a current in its secondary winding proportional to the current flowing
in its primary. They are commonly used in metering and protective relaying in
the electrical power industry where they facilitate the safe measurement of
large currents, often in the presence of high voltages. The current transformer
safely isolates measurement and control circuitry from the high voltages
typically present on the circuit being measured.