Originally Posted by MediaGuy

It's commonly used in exterior conditions to create large, industrial joints and connections for trunk lines and high-tension electrical cabling. Ok. These things aren't found in buildings, they connect generating stations to centrals or transmission stations, substations, and the like, but the "smaller" extensions and connections are branched to progressively smaller network nodes and sub-transmission points (I don't know the technical terms) where the kind of thermite welding you're talking about is not found.