CT Ratio

The primary current of the CT should be equal to the load current of the feeder or the nearest standard rating available and the secondary current of the CT should be that of the meter in the metering cubicle (1A or 5A).

"In general, ct ratios are selected to match the maximum load current requirements, i.e., the maximum design load current should not exceed the ct rated primary current. The highest ct ratio permissible should usually be used to minimize wiring burden and to obtain the highest ct capability and performance. The ct ratio should be large enough so that the ct secondary current does not exceed 20 times rated current under the maximum symmetrical primary fault current."