@Starbruin: Sorry, i misread your post in the first place, i though you were talking about the grid transformers. Now that i read your post again, you were talking about an indoors transformer. My bad.
The wiring can be pretty much anything in the old houses. I remember when 15 years ago my friends parents were thinking about repairing their houses wiring due to fuses burning pretty often and some electrical equipments blowing up sometimes. They called and electrician to check out the need and redo the wiring if needed. In the end, the voltage was pretty random when measured from the plugs and one plug gave more than 300 volts output. Apparently some wire had a loose connection.
@omgwtfbbq: If you live in an apartment, the houses electrical center should have surge protectors. Fuses and circuit breakers, then again, are in the apartments.