A current transformer system with characterization is disclosed. The current transformer system (100) comprises at least one current transformer unit (102) generating a secondary current output (112) relative to a primary current input (110), and a characterizing circuit (104) storing a set of characteristics measured under test conditions in a memory of the characterizing circuit which characteristics represent the relation between the primary current input (110) and the secondary current output (112) of the current transformer unit (102) under various operating conditions, the characterizing circuit (104) further communicating at least one of the characteristics via the communication interface (106) to an onward device to allow dynamic compensation for any errors in the characteristics of the at least one current transformer unit (102) at the device.