1.Please confirm that the "80m cable" is the distance the CT secondary cables will run between the external CT and the PM8000. This would mean that each CT will be driving 160m of wire plus the few milliohms in the PM8000 input terminals.
2. A significant influence factor on CT secondary is the effect that the secondary burden impedance plays on the ratio error and phase error of the instrument transformer. This is not the usual term for line loss (applicable for power distribution/transmission on the system). There seems to be confusion - Transformer and Line loss (solutions implemented in the default templates of some ION meters but not in PM8000) perform real-time compensation for primary system side losses in power. For PM8000 we have Instrument Transformer Correction (ITC), which is designed for ratio and phase error in the CT and PT outputs.
3. bfo case 20631742 has been created for your issue