Again, at the end of the day- if your problem is you are killing DZ2500s and you think it is related to derailments or use of anti derailing sensing- you need to solve that- using TVS- not changing your transformer.
First- Z stuff recommends using regular diodes in series with the sensing rails. This is a reasonable first layer of protection, but if you need more than that, Simply put a properly rated TVS across sense leads to common. This would then kill off any voltage spike.
Second- then put a TVS or multiple in your accessory power bus feeding the DZ2500 switch machines. This prevents a voltage spike from entering the switch motor electronics via the aux power source.
This PDF is the one from Z stuff https://www.zstuffexpress.com/...87963dea595ccef9.pdf
However, we can take it further and additional TVS protection.
Example TVS value 1.5KE36CA- note the CA is important as you need bi-directional versions.
