Automatic Transfer Switch

Yes. It is done with a walking beam. (Looks like a teeter-totter)

Standard catalogue item.

First, you have not mentioned the size of your generator. Second, what is the fault current rating of your equipment and devices compared to you available fault and your breaker/fuse curves.

Generically speaking most of what you have mentioned is usually done with relay protection. Those relays may be mechanical or electrical in operation. Which ever they are they must be able to react in fractions of a second to prevent overcurrent damage.

My personal preference for ATS systems has always been L-shaped (90°) knife blades. When one end of the blade is connected to the mains, the other end is pointing straight out, and cannot connect to the generator. The opposite direction is also true.

This design is simpler & more reliable than a 2-contactor or 2-breaker system. A single-solenoid system provides an integral electrical interlock, and the L-shape blades make it physically impossible to connect the sources together, so it has an inherent mechanical interlock.

Fewer parts also means fewer fail points.

The generators differ in size, it is the principle of using interlocked contactors in an ATS panel that interests me. I think that I have seen a PDF document which referred to the type of L shaped blade contactor to which you refer. Could you give me a model number and name of a manufacturer of such a device?

I would be interested in the make / break capacity of your system. I always found knife switches were only rated for minimal capacities switching under load.