The TVS diodes actually protect the CT. Without them, the CT would try to produce a voltage against an infinite resistance and produce very high internal voltage that can (and does) damage the CT. So it’s considered generally safe to unplug a TVS protected CT while working on it. If you are going to leave a CT unplugged for more than a few hours, I’d recommend removing it from the primary, or shorting the 3.5mm jack (won’t hurt the CT).
No. The IoTaWatt has it’s own TVS diodes inside, primarily to guard against static discharges. They are “rail-to-rail” diodes so they protect all of the internal components. As part of the safety and emissions testing, IoTaWatt has been tested against repeated discharges of thousands of volts.
No, best practice would be to just plug and unplug TVS protected CTs without powering down the IoTaWatt. There are no ordinary configuration procedures that require powering it down or restarting it. For the few configuration changes that require restart, like changing the external name, it’s done automatically.
Pulling the power plug should only be necessary if you need to open the IoTaWatt to remove the SDcard or replace the battery, or in the rare instance it is advised as part of a diagnostic or recovery procedure. Disconnecting the 9V reference should never be necessary.
It does not matter if the CT is connected to the IoTaWatt when you clamp or unclamp a TVS protected CT. Unprotected CTs should be connected to the IoTaWatt before clamping to protect the CT.
If you want to shut down, then yes, just disconnect the USB power.
Thanks for those questions. I now realize that these things need to be explained in the documentation, which I have neglected lately. I have a short list of new things to add, and I’ve put these on it.