The load of the devices to be connected to the current transformers must be carefully sized to indicate the compatible standardized load current transformer. However, since the apparatus is connected to the transformers by means of wires, generally of large length, it is necessary to calculate the power dissipated in these conductors and to add it to the power of the corresponding apparatus.
The current transformers must be pointed according to the load that will be connected in their secondary and this way, NBR 6586/92 standardizes the secondary loads.
For a current transformer, the secondary load simulates the ohmic value of the impedances imposed by the different devices connected to its secondary, including the interconnecting conductors.
By meaning, nominal secondary load is the impedance attached to the secondary terminals of the current transformer, with a value similar to the guaranteed accuracy power, under rated current.
It should be noted that when the nominal secondary current is different from 5 A, the values of the loads must be corrected by the square of the relation between 5A and the corresponding nominal secondary current in order to achieve the desired values of said parameters.