Power Lines

Terminology

• the power industry refers to "transmission" lines which carry electric current from point to point
  • these are usually large structures, above ground, carrying very high voltages
• "distribution" lines or networks deliver the power to the places it will be used
  • this often involves branching/splitting or traveling underground
• together, "transmission and distribution" indicate the whole process, or "T&D" for short
  • e.g. industry magazine Transmission & Distribution World

Data Formats

• there is no common format for power line data
• unfortunately, power companies and power line software apparently use an assortment of GIS, CAD and database storage methods with no standardization for either representation or attributes
• ESRI has some proposed standardization, described in ArcGIS Data Models - Electric Distribution (pdf)
  • It specifically covers distribution (from the substation to the consumer) rather than transmission (from the source to the substation)

Data Sources

• for the USA, some of the USGS topo maps contain printed representations of the locations of transmission lines (but not distribution) as you can see the following USGS DRG
• the pattern is dash-dash-dash-dash-dot, with solid dots indicating non-specific locations of tower structures and hollow dots (small squares) indicating specific locations of tower structures:
  
• this information is encoded into USGS DLG (described on the page Vector Data Sources)
• the lines are present in the DLG layer "MTF" - "Miscellaneous Transportation Features"
• vectors indicate lines, and special nodes indicate specific tower locations as in the following DLG rendering:
  
• a great deal of information is absent - tower type, number of conductors etc. so that would have to be filled in from observation or other sources
• the data is also not necessarily current; most DRG/DLG date back to the 1970s, although reportedly few long-distance transmission lines have been built since that time
• however, in theory, if one put all the DLGs together, and stitched the topology, that would produce a free, precisely georeferenced map of every major transmission line in the USA

Power Data Statistics

• prominent company: RDI, Resource Data International (now owned by Platts?)
• press releases like "Resource Data International Wins Grand Prize for Electric Power System Map"
• PowerMAP spatial products suite
• "The heart of RDI’s business are the comprehensive energy industry database/information systems: POWERdat, COALdat, and GASdat, Covering the electric power, coal, and natural gas markets."