What is the function of current transformers (CTs) in switchgear?

Current transformers (CTs) serve a critical role in switchgear by reducing high current levels to measurable values. They are specifically designed to take high currents, which can be difficult to measure directly due to their magnitude, and produce a lower, proportional current that can be accurately measured by standard instrumentation.

This function is vital for various applications, including protection and metering. For protection, the reduced current allows protective relays to operate effectively without being overwhelmed by the magnitude of the current in the power lines. In metering, this scaled current enables the use of standard ammeters and energy meters to monitor consumption accurately.

The design and operation of CTs also ensure that the secondary current is safely contained and suitable for devices that can read and interpret this lower current, providing an essential measure for both safety and monitoring purposes within electrical systems.