A wide area synchronous grid, or "interconnection" is a power 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 European UCTE with 603 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 UCTE 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 in order 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 an average of 60Hz, while those of Europe run at 50Hz. 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.
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 23 European countries, 603 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.
Planned Interconnections
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 IPSUPS 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.
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