What is the purpose of current and voltage transformers in power systems?

Current transformers (CTs) and voltage transformers (VTs/PTs) provide scaled-down, isolated signals for metering and protection. CTs transform high currents to standard 1A or 5A secondaries; VTs transform high voltages to standard 120V or 69V. This allows standard relays and meters to be used at any voltage level while providing personnel safety. CT accuracy classes (0.3, 0.6, 1.2) indicate metering precision; relay-class CTs emphasize accuracy during faults.