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).
All of the interconnects in North America are synchronized at a nominal 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.
Advantages and Issues
Wide area synchronous networks improve reliability and permit the pooling of resources, they can level out the load, which reduces the required generating capacity, allow more environmentally friendly power to be employed, can permit more diverse power generation schemes, and can permit economies of scale.
Wide area synchronous networks cannot be formed if the two networks to be linked are running at different frequencies or have significantly different standards. For example in Japan, for historical reasons, the northern part of the country operates on 50 Hz, whereas the southern part uses 60 Hz. This makes it impossible to form a single synchronous network, and this was problematic when the Fukushima Daiichi plant melted down.
Also, even when the networks have compatible standards, failure modes can be problematic. Phase and current limitations can be reached which can cause widespread outages. These kinds of issues are sometimes solved by adding HVDC links within the network which permit greater control during off-nominal events.
As discovered in the California electricity crisis, there can be 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 make such manipulations more difficult.
|Name||Covers||Generation capacity||Yearly generation||Year/Refs|
|UCTE||synchronous zone serving 24 European countries, serving 450 million||667 GW||2530 TWh||2009|
|Eastern Interconnection||eastern US and Canada||610 GW|
|IPS/UPS||12 countries of former Soviet Union serving 280 million||337 GW||1285 TWh||2005|
|Western Interconnection||western US, Canada, and north western Mexico||265 GW||883 TWh||2015|
|Indian national grid||India||232 GW||914 TWh||2013|
|NORDEL||Nordic countries synchronous zone (Finland, Sweden, Norway and Eastern Denmark) serving 25 million people.||93 GW||390 TWh|
|ATSOI / UKTSOA||Ireland and Great Britain's synchronous zone, serving 65 million.||85 GW||400 TWh|
|National Electricity Market||Australia's States and Territories except Western Australia and the Northern Territory.|
|SEMB||South Eastern Mediterranean Block serves Libya, Egypt, Syria, Jordan and Lebanon.|
|SWMB||South Western Mediterranean Block serves Morocco, Algeria and Tunisia.|
|Southern African Power Pool||SAPP serves 12 countries in Southern Africa.|
- 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.
Planned non synchronous connections
- 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: 4. Retrieved 2008-12-06.
- Haubrich, Hans-Jürgen; Dieter Denzel (2008-10-23). "Characteristics of interconnected operation" (PDF). 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: 2.
- Sergei Lebed RAO UES (2005-04-20). "IPS/UPS Overview" (pdf). Brussels: UCTE-IPSUPS Study presentation: 4. Retrieved 2008-12-07.
- 2016 State of the Interconnection page 10-14 + 18-23. WECC, 2016. Archive
- "Growth of Electricity Sector in India from 1947-2013" (PDF). Central Electricity Authority, Ministry of Power, Government of India. July 2013. Retrieved 20 February 2014.
- 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. Check date values in:
- Sergey Kouzmin UES of Russia (2006-04-05). "Synchronous Interconnection of IPS/UPS with UCTE - Study Overview" (pdf). Bucharest, Romania: Black Sea Energy Conference: 2. Retrieved 2008-12-07.
-  A Wide Area Synchronized Frequency Measurement System