What can we do if the rated burden for a current transformer was not adequate for the application?

In order to determine the minimum burden requirement for a given current transformer, you need to calculate both the burdens from the connected measuring instruments (or protection devices) and the power losses in the secondary wiring.
In case the calculated sum exceeded the rated burden value of the current transformer you can try the following:

• Consider the use of 1A secondary current instead of 5A; the use of 1A secondary current reduces the wiring losses by a factor of "25" compared to losses with 5A secondary, see attached table as an example.
• Consider using a bigger wire cross section for secondary wiring; as the bigger the cross section the lower the losses expected per unit lenght.

Released for: Schneider Electric Canada