shorting behavior of isolation transformer
Overcurrent does not damage a transformer, it's over temperature that's the problem.

When a transformer output is short-circuited, there's a large increase in current in both secondary and primary windings. If this is allowed to continue, it will eventually overheat it, and destroy the insulation. However, it will take many, many seconds to reach a dangerous temperature, plenty of time for a fuse or breaker to respond, so it can be completely protected by using a suitable fuse or breaker.

It's more of a problem to protect against 50% overcurrent, as a fuse that's going to blow at 50% above nominal will run very hot, and may nuisance blow on switch-on transients. A time delay fuse is essential to resist the switch-on transients.

A breaker can be set more accurately than a fuse, and is a better bet if you also want protection from small amounts of overload.

Small overloads will take 10s of minutes to overheat the transformer, so the best protection against small overloads is the use of a thermal breaker attached to the transformer.