PTs and CTs

Instrument transformers are high accuracy class electrical devices used to isolate or transform voltage or current levels. Instrument transformers are commonly used with instruments and/or meters to isolate secondary control circuitry from high voltages or currents. The primary winding of the transformer is connected to the high voltage or high current circuit, and the meter or relay is connected to the secondary circuit. Instrument transformers are primarily classified into two types: current transformers (CT) and potential transformers (PT).