Wide area synchronous grid
A wide area synchronous grid, also called an "interconnection" in North America, is an electrical grid at a regional scale or greater that operates at a synchronized frequency and is electrically tied together during normal system conditions. These are also known as synchronous zones, the largest of which is the synchronous grid of Continental Europe (ENTSO-E) with 667 gigawatts (GW) of generation, and the widest region served being that of the IPS/UPS system serving countries of the former Soviet Union. Synchronous grids with ample capacity facilitate electricity market trading across wide areas. In the ENTSO-E in 2008, over 350,000 megawatt hours were sold per day on the European Energy Exchange (EEX). As discovered in the California electricity crisis, there are strong incentives among some market traders to deliberately create congestion and poor management of generation capacity on an interconnection network to artificially inflate prices. Increasing transmission capacity and expanding the market by uniting with neighboring synchronous networks will make such manipulations more difficult.
All of the interconnects in North America are synchronized at 60 Hz, while those of Europe run at 50 Hz. Interconnections can be tied to each other via high-voltage direct current power transmission lines (DC ties), or with variable frequency transformers (VFTs), which permit a controlled flow of energy while also functionally isolating the independent AC frequencies of each side.
The benefits of synchronous zones include pooling of generation, resulting in lower generation costs; pooling of load, resulting in significant equalizing effects; common provisioning of reserves, resulting in cheaper primary and secondary reserve power costs; opening of the market, resulting in possibility of long term contracts and short term power exchanges; and mutual assistance in the event of disturbances.
Major existing networks
- Eastern Interconnection — serving eastern US and Canada; 610 GW of generation.
- Western Interconnection — serving western US, Canada, and north western Mexico; 160 GW of generation.
- National Electricity Market — one of the world’s longest interconnected power grids, serving all Australia's States and Territories except Western Australia and the Northern Territory.
- NORDEL — Nordic countries synchronous zone (Finland, Sweden, Norway and Eastern Denmark), 93 GW generation capacity, 390 TWh per year, serving 25 million people.
- UCTE — synchronous zone serving 24 European countries, 667 GW generation, 2530 TWh per year, serving 450 million
- ATSOI / UKTSOA — Ireland and Great Britain's synchronous zone, 400 TWh per year, 85GW generation, serving 65 million.
- IPS/UPS — 12 countries of former Soviet Union: 337 GW generation, 1285 TWh annually, serving 280 million 
- SEMB — South Eastern Mediterranean Block serves Libya, Egypt, Syria, Jordan and Lebanon.
- SWMB — South Western Mediterranean Block serves Morocco, Algeria and Tunisia.
- SIEPAC serving 37 million customers of 6 countries of Central America.
- China plans to complete by 2020 its ultra high voltage AC synchronous grid linking the current North, Central, and Eastern grids. When complete, its generation capacity will dwarf that of the UCTE Interconnection.
Proposed mega grids
- Union of the UCTE and IPS/UPS grid unifying 36 countries across 13 time zones.
- Unified Smart Grid unification of the US interconnections into a single grid with smart grid features.
- SuperSmart Grid a similar mega grid proposal linking UCTE, IPSUPS, North Africa and Turkish networks.
- High-voltage direct current (HVDC)
- Super grid
- European super grid
- Smart grid
- Unified Smart Grid
- SuperSmart Grid
- Tres Amigas SuperStation
- EEX Market Monitor Q3/2008 (pdf). Leipzig: Market Surveillance (HÜSt) group of the European Energy Exchange. 2008-10-30. p. 4. Retrieved 2008-12-06.
- Haubrich, Hans-Jürgen; Dieter Denzel (2008-10-23). "Characteristics of interconnected operation". Operation of Interconnected Power Systems (pdf). Aachen: Institute for Electrical Equipment and Power Plants (IAEW) at RWTH Aachen University. p. 3. Retrieved 2008-12-06. (See "Operation of Power Systems" link for title page and table of contents.)
- UCTE-IPSUPS Study Group (2008-12-07). Feasibility Study: Synchronous Interconnection of the IPS/UPS with the UCTE (pdf ). TEN-Energy programme of the European Commission. p. 2.
- Sergei Lebed RAO UES (2005-04-20). IPS/UPS Overview (pdf). Brussels: UCTE-IPSUPS Study presentation. p. 4. Retrieved 2008-12-07.
- Liu Zhengya President of SGCC (2006-11-29). Address at the 2006 International Conference of UHV Transmission Technology. Beijing: UCTE-IPSUPS Study presentation. Retrieved 20068-12-06.
- Sergey Kouzmin UES of Russia (2006-04-05). Synchronous Interconnection of IPS/UPS with UCTE - Study Overview (pdf). Bucharest, Romania: Black Sea Energy Conference. p. 2. Retrieved 2008-12-07.
-  A Wide Area Synchronized Frequency Measurement System