For the meters, sniff around the “fastest” wheel on the registers with an ordinary magnetic compass. If there’s a magnet in there, that should see it. If you have dials and pointers (still!), it’s a whole lot harder and probably not feasible to detect the pointers (though I did read a long time ago about using a computer mouse to detect the pointer going past - not here though). I rather doubt there’s a magnet in the electricity meter, you’re most likely going to need an optical sensor there to count disc revolutions.
The short answer to the Pi is you can’t by design because of the absence of connectors on the outside. (Or more precisely, there’s provision for only one on the RJ45 I/O connector.) If you’re willing and able to get wiring into the case, then try this Directly connecting to Optical Pulse Counter with RPi? - #2 by pb66
You can calculate the supply impedance (fault level) from that. 
In the 1980s, I worked on projects electrifying the winding engines at collieries. It was often said that in the village, they could count how many skips of coal came up on the night shift because all the light dipped each time the winder motor started. (In one case, the motor was 4000 H.P (~ 3 MW), d.c., pulling 8 kA during acceleration.)