Luckily, 100mS is pretty slow.
A MEGA 2560 has plenty of inputs, and would handle that easily.
The greater problem to consider, is how far from. and between the meters and your logging location.
Getting the data to csv is easy, , and you have a few options to put the data on the LAN, that’s a separate conversation.
Because you’re working in an industrial location, I’d be thinking about opto isolation between the meters and the logger inputs..