In Europe, houses often have all breakers chained beneath one or more RCDs (their word for GFCI). I would not want the nuisance of multiple circuits shutting off at once, so I'm glad in the US we have GFCI on individual breakers or outlets. But, I would like to have some sort of alarm sound when leakage current of my home as a whole exceeds some level or increases rapidly.
At first thought a CT around the grounding conductor in the main panel would do this. But this would not detect leakage through Earth/water/communications cables. Paths to ground are essentially unlimited, and impossible to enumerate.
So what about measuring the utility conductors? With a single hot like they have in Europe this would be easy because there's only one path current should be taking for each customer. If the current on their utility's hot != the current on their utility's neutral, then the difference is leakage.
But with the NorthAmerican split-phase system you can't assume L1=L2 or L1+L2=N can you?
Is there mathematically, a way to detect the amount of leakage current by measuring only L1, L2, and N in a standard North American residence? I'm guessing not, but I'm hoping someone here can blow my mind.