A current transformer (CT) reduces high alternating currents (AC) to a lower, safe, and proportional value for precise measurement and protection. By converting large primary currents into manageable secondary currents (typically 1A or 5A), CTs allow standard instruments and relays to monitor, measure, and protect electrical systems without direct contact with high-voltage circuits.

Key Purposes of a Current Transformer:
Safe Measurement: They isolate measuring instruments (like ammeters and wattmeters) from high-voltage primary circuits, preventing damage and protecting personnel.
Protection of Equipment: They provide accurate, real-time data to protective relays and breakers, enabling them to detect faults or overloads and quickly shut down the system.
Current Reduction: They step down, or scale down, high-load currents to low-level currents that are easy to measure and handle.
Energy Metering: They enable accurate monitoring of energy consumption for billing purposes in residential and commercial settings.