OCFA Securing Utilities Practice Test

In underground distribution, the device that brings customer voltage down from the higher distribution level to usable service levels sits on a concrete pad at ground level—this is a pad-mounted underground transformer. It’s a weatherproof, sealed enclosure that houses the transformer and protective gear, designed for easy access by utility crews with the appropriate keys. The unit takes the medium-voltage supply carried underground (often several kilovolts) and steps it down to the standard customer voltages (such as 120/240 V or 208Y/120 V), delivering power directly to homes or businesses from a location near the curb or the building.

This setup is distinct from overhead transformers, which are mounted on poles, and from substation transformers, which operate at higher power levels inside a substation. The pad-mounted design is specifically tailored for underground networks, enabling safe, reliable service delivery at street level.