I think you are going to need to give us a few more details
- brand and model of drive
- fault code
Phase currents and phase voltages can vary a bit. Our older drives are Siemens CUVC, mitsubishi A560. Newer are Mitsubishi A760 and A860. Motor ground faults don't trigger until 33% - 50% ground fault current. Phase imbalance is in the range of 10% of rated drive output before it trips.
It is tough to measure the voltage and current while the drive is running, particularly at low speeds. I have not found a meter that will average consistently enough to give me a decent reading
With no info on the drive you have, I would expect instantaneous to be peak, or instant. RMS stands for Root Mean Square, and requires averaging by the meter.
The CTs on a drive are designed to respond to the frequencies generated by the drive. These are filtered before being displayed on the keypad. Tthe carrier frequency, or the frequency of the pulses generated by the drive, is normally 500 Hz for large drives, up to 16 Khz ... depending on efficiency and design
Does that help at all?
If this is causing you downtime, I'd start with replacing the motor. We have motors that test fine, but that cause problems with our drives. I have changed out maybe 10 or 12 motors for this reason in the past 10 years.