HMV Barn Project

[ppppenguin]

I'm curious as to why these wires are sleeved in larger cables that internally are connected to a ground. That is, you have a black wire that runs to the grid, for example, and the outer wire it runs internally through will have its inner core grounded to some point.

This sounds like you are describing a screened cable. Just like co-ax. The purpose of the outer earthed screen is to shield the sensitive circuit in the middle from picking up hum and noise.