A current transformer must be loaded with an extremely low impedance. (In addition use great care in using current transformer if the output is open circuit).
You will have much greater success if you use a current transformer then connected to a HIGH impedance
opamp gain block to raise the millivolt level signals from the transformer load resistor. This gain block can raise the working voltage to volts level resolution where it can then be averaged via a R/C filter. The filter output can drive the ADC input to the microcontroller.

Michael Karas