European network

This article deals with the pan-European electricity network, for other interconnected networks see under interconnected network .

The European Verbundsystem (EV) is a Europe-wide, close-meshed power network consisting of high and extra- high voltage lines for the distribution of electrical energy . Although there are several separate interconnected systems in Europe due to the spatial division, the European interconnected system is generally understood to mean the central European network of those countries which comprise the former Union for the Co-ordination of Transmission of Electricity (UCTE) ("UCTE-Verbundnetz ").

The European network system is operated with three-phase alternating current in the form of three-phase high-voltage transmission , the exchange of electrical energy takes place on the transport network level with high voltages of 220 kV and 400 kV between the various network operators. The advantage of such a network is that fluctuations in consumption and generation can be balanced out much better than if each country or region had a stand-alone power supply network.

General

European network systems, color-coded network networks. The spatial area of ​​the continental European network (formerly UCTE) is blue. Network areas outside Europe not shown.

In addition to the continental European network (formerly UCTE), there is also the network of the northern European states NORDEL in Europe and the UKTSOA in Great Britain . The Russian network system IPS / UPS has the largest spatial expansion . It stretches from Estonia , Latvia and Ukraine to the Asian region. All networks mentioned are connected to one another by means of high-voltage direct current transmission (HVDC). Only islands like Iceland and Cyprus have their own stand-alone grid without a connection to the European network.

In addition, some regions and countries outside Europe are integrated into the European network, in addition to Turkey the North African countries Morocco , Algeria , Tunisia and Western Sahara . The North African countries are technically synchronously coupled via an AC voltage connection between Spain and Morocco, due to the comparatively small power this is technically possible, and the control equipment in the larger caloric power plants in the North African countries is designed so that synchronous operation with Europe is guaranteed. Since April 15, 2015, the Turkish power grid has been synchronously connected to the European grid. The first synchronization took place on September 18, 2010; then full synchronization was gradually achieved in three phases. As of 2016, Turkey is connected with three 400 kV transmission lines; two lines lead to Bulgaria, one line to Greece.

There are technical reasons why Great Britain and the Northern European countries have their own interconnected networks that are not synchronous with the continental European interconnected network. Among other things, three-phase alternating current of higher power cannot be transmitted via the necessary longer submarine cables . Direct current in the form of high-voltage direct current transmission (HVDC) must be used for the electrical energy exchange, which means that there is no synchronicity between the interconnected networks. Examples of such submarine cable connections between the UCTE network and Great Britain and the Northern European countries are the HVDC Konti-Skan , HVDC Cross-Skagerrak , BritNed or the NorNed .

A small, independent network system, which for historical reasons is used exclusively for rail operations with a network frequency of 16.7 Hz, exists between the rail power networks in Germany, Austria and Switzerland. In other countries, the electricity for rail operations is taken directly from the general network. This is possible because the railways there are operated either with direct current or alternating current of 50 Hz, which can be converted from the integrated network with much less technical effort.

properties

Variation of the network frequency over 48 hours in different 50 Hz network networks, European network in green

Each network system is characterized by the fact that all generators and power plants work in it synchronously, i.e. with an identical network frequency and corresponding phase position . This means that they can be connected together electrically in substations using power transformers . If the frequency or phase position were not exactly the same for all generators in the case of alternating voltage , short circuits would be the result. Adjacent interconnected networks can be equipped with nominally the same network frequency of, for example, 50 Hz, but due to ongoing minor fluctuations in the nominal frequency, the specific values ​​are not identical, which means that no direct electrical network can be established.

Each network system is divided into several control areas. For example, Germany comprises four control areas, Austria and Switzerland each have a control area, each with a transmission system operator who acts as control area manager. One of the tasks of the control area management is to coordinate the control power to be provided by the network operators . The reason is that electrical power grids, and also interconnected grids, cannot store electrical energy. At all times, the generated electrical power must correspond to the demanded electrical consumption, otherwise the network frequency in the entire interconnected network deviates upwards (insufficient demand) or downwards (too high demand).

These deviations are marked on the transport network level by corresponding power flows as compensation and in extreme cases can lead to overloading of the lines and transformers. Therefore, if there is a deviation that exceeds or falls below certain tolerance thresholds, this must be compensated within the framework of the network control and via control power, whereby electrical energy can also be exchanged between the control areas for the purpose of balancing the balance. This means that the reserve power in an interconnected network can be lower than in small island networks . In 2010, for example, an average of around 3 GW of primary control power was kept in the entire UCTE network, the frequency gradient of the control power in the European network is around 20 GW per Hz deviation of the network frequency. If the network frequency deviates significantly from the nominal frequency due to balance deficits, such as underfrequency , emergency measures are taken, which in extreme cases can lead to power failures and the temporary separation of the network into several independent sub-networks.

The following table summarizes some of the key figures for the interconnected networks in Europe:

Transport services

Network	Installed power [GW]	Peak load [GW]	Consumption [TWh / a]	Population [million]
UCTE	631	390	2530	450
NORDEL	094	066	0405	024
UKTSOA	085	066	0400	065
IPS / UPS	337	215	1285	280

Disruptions

See also : List of historical power outages

Even in a large, transnational network, major incidents can never be completely ruled out or avoided. The quality of supply in the European interconnected system is high compared to other interconnected networks, as shown in the figure on the right (grid frequency curve over 48 hours). Large deviations in the network frequency from the nominal value of 50 Hz downwards or upwards indicate greater differences in the balance between supply and demand. More precise analyzes, for example whether the deviations show more low-frequency components as in the NORDEL network or rather high-frequency components such as in the UKTSOA network, allow conclusions to be drawn about the control properties of the respective network and the behavior in the event of incidents.

Examples of major disruptions in the UCTE network:

• On September 28, 2003 the power went out for more than 15 hours in almost all of Italy. Parts of France, Switzerland and Austria were also briefly affected. The cause was a short circuit at around 3 a.m. on the Lukmanier line in Switzerland. Since the corresponding loads were not removed from the grid quickly enough within Italy, the line failed to restart and, in a chain reaction, all other connecting lines between Italy and its neighbors were shut down due to overload. Italy, which is dependent on electricity imports, was no longer able to maintain its own electricity network after being separated from the European network. Rebuilding the network took between 5 and 18 hours, depending on the region.
• When there was a power failure on November 4, 2006 , parts of the network in Western Europe failed for about an hour from around 10 p.m. The cause was related to a scheduled (but poorly planned or prepared) shutdown of a 400 kV high-voltage line across the Ems near Papenburg . This led to an overload of several connecting lines.
• At the beginning of March 2018 it became known that the grid frequency had been just below the target value of 50 Hertz for an exceptionally long time  . This was made practically visible by the fact that synchronous clocks such as B. some clock radios, which determine their clock based on the network frequency, slowed down by about 5 minutes. The cause of this phenomenon was insufficient control power . On March 6, the ENTSO-E confirmed that 113 GWh of energy had not been fed in in the control area of ​​Serbia, Macedonia, Montenegro (SMM Block), especially in Kosovo and Serbia ,  since mid-January . A political solution to disagreements between the Serbian and Kosovar authorities was called for.

Possible future concept

Concept planning of a fictitious supergrid to link the renewable energy generation regions in North Africa with the consumption points in Europe ( DESERTEC )

A supergrid is a power grid that connects areas that are far apart from one another using powerful power lines, usually using HVDC technology . Supergrids are seen as an important element of a future electricity system in order to stabilize the increasingly fluctuating electricity production by connecting different regions with the expansion of wind power and photovoltaic systems and thus to minimize the expansion of storage power plants . Basically, long-distance transmission using HVDC is generally economically superior to the storage of electricity and should therefore be preferred if possible.

There are various plans for supergrids around the world. These include For example, the supergrid that is supposed to connect Europe and North Africa in the "DESERTEC" concept, as well as the European North Sea network, which is supposed to network several North Sea countries and a large number of offshore wind farms . In addition, further proposals were made for supergrids in North and South America, Russia and Eastern Europe, Australia and Tasmania, China and Southeast Asia and the Middle East.

A planned Europe-wide wide area high-voltage network is called a European supergrid . This could serve in particular for the exchange of fluctuating renewable energies over long distances. It is intended to help compensate for the regional differences in production due to the weather .

From a technical point of view, meshed HVDCs of high capacity were not feasible as of 2011, so that HVDCs, apart from a few systems with simple branches, were limited to endpoint connections between two converter stations . In the usual meshed AC voltage networks based on three-phase high-voltage transmission , in addition to the parameter of the node voltages, the phase position and, linked to this, the parameters of the active power and the reactive power are available. As of 2015, however, thanks to the advances in power electronics, there were already high-voltage circuit breakers for direct current, which, thanks to the ability to separate cables individually from the overall network in the event of network faults, will allow the construction of cables with branch nodes as well as meshed direct current networks.

literature

• Adolf J. Schwab: electrical energy systems . 4th edition. Springer, 2015, ISBN 978-3-662-46855-5 .

Web links

• Homepage ENTSO-E - European Network of Transmission System Operators for Electricity
• Measurement of the mains frequency, phase angle with respect to 50.0 Hz and the DCF77 time
• Wired Europe! - The biggest obstacle to phasing out nuclear power is the lack of power lines. A super network would be the solution - with Norway as the battery
• Real-time monitoring of the power grid frequency, operated by Swissgrid

Individual evidence

1. ^ Expanding the European Electricity Market. (No longer available online.) ENTSO-E , April 16, 2015, archived from the original on July 9, 2015 ; accessed on July 8, 2015 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.   
2. ^ Turkey's elec. link to European network 'win-win' step. (No longer available online.) Aaenergyterminal.com, April 17, 2015, archived from the original on July 9, 2015 ; accessed on July 8, 2015 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.   
3. ↑ Trial parallel operation with TEIAS to proceed to the final phase on June 1. (No longer available online.) ENTSO-E, archived from the original on July 9, 2015 ; accessed on July 8, 2015 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.   
4. ↑ Consolidation of control areas into a single one in Austria, pp. 3–4
5. ↑ Network regulation in Switzerland: From seven to one control area with cross-border power provision
6. ↑ EU - Russia Energy Dialogue  ( page can no longer be accessed , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. , Lecture, queried September 7, 2011  
7. ↑ UCTE's final report on the power failure in Italy (PDF; 2.3 MB; eng.)
8. ↑ Final report of the UCTE and finally on the power failure in Western Europe (PDF; 2.7 MB; eng.)
9. ↑ Presentation of the final report of the UCTE on the power failure in Western Europe (PDF; 145 kB; eng.)
10. ↑ heise online: Time synchronization via the power grid: A shortage of energy makes clocks slow. Accessed March 6, 2018 (German). 
11. ↑ [Press Release] Continuing frequency deviation in the Continental European Power System originating in Serbia / Kosovo: Political solution urgently needed in addition to technical. Retrieved March 6, 2018 (UK English). 
12. ↑ Thomas Klaus et al .: Energy target 2050: 100% electricity from renewable sources . 2010, p. 132 ( project brochure as PDF - publisher: Federal Environment Agency). Project brochure as PDF ( memento of the original from July 22, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  
13. ↑ Homepage: The North Seas Countries Offshore Grid Initiative
14. ↑ ^{a b} Mark Z. Jacobson , Mark A. Delucchi, Providing all global energy with wind, water, and solar power, Part II: Reliability, system and transmission costs, and policies . In: Energy Policy 39, Vol. 3, (2011), 1170–1190, doi : 10.1016 / j.enpol.2010.11.045 .
15. ↑ Volker Quaschning , System technology for a climate-friendly energy supply in Germany for the 21st century , Düsseldorf 2000, p. 150.
16. ↑ Burkhard Straßmann: Wired Europe! Zeit.de, April 13, 2011, p. 2 , accessed on September 5, 2011 . 
17. ↑ Michael Sterner : Network expansion vs. Storage vs. Energy management? 2010, p. 6 ( presentation slides as PDF - presentation at the Fraunhofer IWES annual conference EE10, Berlin, October 26, 2010). Presentation slides as PDF ( memento of the original from November 5, 2012 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  
18. ^ Adolf Schwab, electrical energy systems . 4th edition 2015, p. 471.