In modern electricity parlance a DNO (distribution network operator), or DisCO (distribution company) or DSO (DNO by other name s/network/system/) operates the network between the transmission system and most of the connected loads, down to the "low voltage" domestic customers.
For the UK, there are multiple sources of distribution system data, for the dozen or so different regional networks.
In some countries there are hundreds of DNOs. The UK has for the last half century and more had only about 12, since the nationalisation of many smaller undertakings in the late 1940s (see this wikipedia List!). These were once called the AEBs (area electricity boards) then the RECs (regional electricity companies) following privatisation in 1990. Indeed, there were plans in the 1970s to combine the AEBs with the CEGB (central electricity generating board -- operator of transmission system and generators) to make a mighty monolithic company ... but instead the privatisation resulted in the CEGB being split into several generating companies and the national grid.
The RECs appear to have maintained their old AEB boundaries in spite of the ownership and branding changing every few minutes (years?). However, it is common that several adjacent REC areas are owned by a single company at any time, making it just a little easier to assemble links to all the data!
The traditional (second half of 20th century) regions are:
England and Wales (approximately clockwise from London/East)
EEB: Eastern Electricity Board
LEB: London Electricity Board
SEEBOARD: South Eastern Electricity Board
SEB: Southern Electricity Board
EMEB: East Midlands Electricity Board
MEB: Midlands Electricity Board
SWEB: South Western Electricity Board
SWALEC: South Wales Electricity Board
MANWEB: Merseyside and North Wales Electricity Board
YEB: Yorkshire Electricity Board
NEEB: North Eastern Electricity Board
NWEB: North Western Electricity Board
Scotland
South East Scotland Electricity Board
South West Scotland Electricity Board
There is scarcely any point in listing the current "owners", as they change so often. Here is an attempt from late 2011.
Eastern England UK Power Networks
London UK Power Networks
South East England UK Power Networks
Southern England SSE Power Distribution
East Midlands Western Power Distribution
West Midlands Western Power Distribution
South West England Western Power Distribution
South Wales Western Power Distribution
North Wales, Merseyside and Cheshire SP Power Systems Manweb
Yorkshire Northern Powergrid (YEDL)
North East England Northern Powergrid (NEDL)
North West Electricity North West
North Scotland SSE Power Distribution
South Scotland SP Power Systems
A major source of publicly available distribution system data is the LTDS -- long-term development statement. This is a five-year plan published annually, required by regulation. Most companies provide a summary of tens of pages openly on the web. Some provide more, even extending to detailed spreadsheets and maps. Some (one?) are more restrictive, with only a tiny summary on the web, and more by application if one appears to have a need. See the government electricity-regulator (OFGEM) page about LTDSs.
As of late 2011, the following companies represent the entire set of GB DNOs. LTDS information can be obtained from the given links: it ranges from an extensive set of reports, spreadsheets and maps, down to a few pages of summary (more on application if "qualified"); the normal is a summary of some 40--80 pages.
Page started: 2011-11-21
Last change: 2011-11-21