Look at this for a great idea, do you ultimately need a relay contact output for your current measurement? Many of the CTs feature a plug in relay module option. Just twist of the secondary terminal covers and remove the secondary terminal screws. Screw in the brass transformer to module connecting studs and plug in the OCR module. The OCR modules provide two volt free contact outputs rated at 5Amps 1N/C and 1N/O, connected to an adjustable time delay to avoid nuisance tripping. The OCR modules always require an auxiliary supply, 24VAC is also possible with the OCR module.