Clark and Park transforms require the instantaneous voltage and current I believe which I assume you are feeding to a micro. (I have to assume all this since you didn't give much info on what you are doing).
For the voltage you can use an isolation transformer for each phase to generate isolated voltages which can be measured with three A/D converters for readout by the micro.
The current can be measured with a current transformer for each phase with their output voltages being measured by another three A/D converters.