1. 11KV Current transformer ct for measurement(or the measuring winding of the current transformer) : it provides the current information of the power grid to the measuring and metering devices within the normal working current range.

2. Protection ct with power current for protection (or the protection winding of current transformer) : in the state of power grid failure, it provides power grid fault current information to relay protection devices.

The roles:

1. Current transformer plays the role of current change and electrical isolation. It is a sensor for measuring instruments, relay protection and other secondary equipment in the power system to obtain the current information of the primary circuit. The current transformer converts high current into low current in proportion.

2. Electtrical current transformer for protection is mainly cooperated with the relay device to provide signals to the relay device to cut off the fault circuit in case of short circuit overload and other faults, so as to protect the safety of the power supply system.