TransFormer Surge Arrestors

You may find that the surge arrestor is not necessarily mounted on the transformer but is a separate unit near it (typically looks like an insulator between the fuse and the transformer but there will be a lead to ground (probably to the ground on the transformer).

Thanks for the informative reply, Don. I looked again and all I can observe between the transformer HV (primary) terminal and the MV feeder is the usual series combination of a manual-reset cutout and a fuse. Also, the replacement transformers, unlike those they replaced, have a (plastic?) shroud that covers about half the length of the transformer's HV terminal insulator.

The surge arrester's principal function is to protect against lightning strikes (or perhaps induced potential from unusual sunspot/auroral activity) so I suppose it could be left out without undue risk for power outages and equipment damage. Or perhaps the replacement units are more robust and don't require an arrester. Sincerely,

The setup can vary from utility to utility- Here only an arrester and a fuse are used-no cutout. The fuses are in tubes and, if I recall correctly the fuse holder acts as a cutout. Some appear to have the arrestor and fuse on a common mount. An underground MV cable has fuse and arrester on the pole where the cable goes down.

Related question: When I was a kid, seemingly older pole transformers often had a thing attached to the pole under the transformer that looked like a large acorn. I don't remember how wires were attached to it other than it was attached to the ground lead running down the pole, but what could this have been? Perhaps a surge arrestor attached to the secondary?

If I recall correctly, that is where the old transformers made their center tap to ground bond. Modern transformers usually have those on the lower part of one of their sides. As with the new, there is a bus bar that worms its way up the guts to the "neutral".