I need the data for the research I am carrying out for a masters thesis. There are a few maps out there (e.g. http://powermin.nic.in/sites/default/files/uploads/powergrid_map.pdf), but they seem more like schemas and would be difficult and very time-consuming to turn into a shapefile.
In the US the FAA has sectional flight maps for Visual Flight, transmission lines are show as navigation aids. By cross referencing these with aerial photography you can digitize a fairly accurate layer. Most power companies do use schematics as the actual position means less then conductivity. However your PDF is a rough guide and will help you identify them. If your stuck digitizing them it's fairly easy as they tend to run in straight lines for mi/km's.