current transformer

A current transformer (CT) is a type of transformer that reduces or multiplies alternating current (AC), producing 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, which scale the large values of voltage or current to small, standardized values that are easy to handle for measuring instruments and protective relays. Instrument transformers isolate measurement or protection circuits from the high voltage of the primary system. A current transformer presents a negligible load to the primary circuit.
Current transformers are the current-sensing units of the power system and are used at generating stations, electrical substations, and in industrial and commercial electric power distribution.

View More On Wikipedia.org