In differential Protection (like in Transformers) we have CT's installed at Primary side and secondary side of the t/f. How is the Differential Protection of the 6600V Induction motor is achieved as the CT's are installed in the panel of Induction motor that too on the feeder of the motor?

Some body told me that Differential CT's are also installed on the Incomer of the switchboard on which Motor panel is installed but he couldn't explain his Answer?