Possible measures to make power supplies safe
To establish the ELV you will need isolation. This will probably be a transformer (Linear or Switchmode does not matter)

Transformers can be protected in a number of ways from faults...


Self Limiting (Internal resistance limits the available power)
The use of Triple Insulated wire (TIW) in the transformer construction. 
Fuses in the primary or secondary depending on the requirements.
Thermal sensor in the transformer (Rare?)
Internal thermal fuses
Over voltage sensing (Most Switch Mode Power Supply IC do this anyway, it's often how they regulate).


Over voltage sensing can be via opto-isolators with zeners or similar .

In the end testing will probably be required unless you buy a pre-evaluated product.

This depends on your end application. There will be a safety aspects in those standards that relate to transformers and their faults. Look at what the requirements are and this determines your minimum effort/cost.
Get your self access to those standards and read them. 

The best way is to be taught by one of the more experienced engineers. Ask them to review a design with you. Trying to read standards the first time tends to drive you crazy with forward and backward references ... oh and the language used between Europe and the US can also make life interesting.