Where does the lineman make the last connection when installing protective grounds?

The last connection made by a lineman when installing protective grounds is at the lightning arrestor. This is because lightning arrestors are critical components in protecting electrical systems from voltage spikes caused by lightning strikes. Making the connection here ensures that any transient voltage will safely divert to ground before it can affect the rest of the system or pose any danger to personnel.

By connecting last at the lightning arrestor, the lineman prevents any inadvertent induction of voltage into the system that could occur while making earlier connections to other components like the power line or transformers. This practice is vital for safety because it ensures that the arrestor is grounded before any live work is performed, reducing the risk of electric shock or equipment damage.

Connecting to other options like ground rods, power lines, or transformers would not provide the same level of protection for the lineman, as these connections could still be active, exposing workers to hazardous conditions.