Current Transformers

Metering CT has much higher accuracy, a faction of a percent. To achieve this , it operates at much lower flux density level, whereas protection CT accuracy does not matter even a few % accuracy.

Lower flux density means bigger core for the same current handling.

Bravo88

Singapore

Measuring CT's for use say with an Energy Meter or an Ammeter are constructed to have a high accuracy over the range 10% to 120% of the rated current, for currents greater than 120% measuring CT core should saturate in order to protect the meters from high fault current therefore the core is comparatively of smaller cross section than a protection CT, nickel - iron alloys are used .

Protection CT's for use with say an overcurrent relay must not saturate corresponding to the maximum fault current in the connected burden, have a larger core cross section, grain oriented steels having high saturation levels are used.