Can you extend the cable to the current transformers?

Yes, the cables for the current transformers can be extended with a twisted pair cable. A pair is required for each current transformer. Total loop resistance should be kept below 10 ohms. The maximum length the cable can have without affecting the measurement accuracy is then given by:

Note that the measurement accuracy can still be affected if long cables run in parallel with other live cables. In such cases, a shielded cable can contribute to reduced crosstalk from the adjacent cables.