2.1 rated capacity: the apparent power consumed when the rated secondary current passes through the rated secondary load. The rated capacity can be used in apparent power V. A means, can also be expressed with the secondary rated load impedance. 

2.2 primary rated current: The current load that is allowed to pass through the primary winding of the current transformer. The primary rated current of current transformer used in power system is 5 ~ 25000A, and the precision current transformer used in test equipment is 0.1 ~ 50000A. Current transformer can be rated current in a long-term operation, load current exceeds the rated current value is called overload, current transformer long-term overload operation, will burn out winding or reduce service life. 

2.3 Secondary Current Rating: Primary induced current that permits passage through the secondary windings of a current transformer. 

2.4 current rating (transformer ratio) : Ratio of primary rated current to secondary rated current.