Wide area synchronous grid
The European grid system is a Europe-wide fine-meshed power grid of high and extra high voltage distribution lines for electric power. Although there exist in Europe due to the spatial division multiple separate composite systems, in general, under the European interconnected system, the Central European interconnected system of those countries understood the Co -ordination of Transmission of Electricity ( UCTE ) include the former Union for the ( " UCTE network ").
The European grid system is powered by three-phase alternating current in the form of three-phase high voltage transmission, the exchange of electrical energy takes place on the transport network layer with high voltage of 220 kV and 400 kV between the various network operators. The advantage of such a network is that fluctuations in consumption and in the production can be considerably better balanced than if each country or region would have a stand-alone power supply system.
General
In addition to the continental European grid (formerly UCTE) exist in Europe the main power grid of the northern European countries and in the UK the Nordel UKTSOA. The spatially greatest extent has the Russian composite system IPS / UPS. It stretches from Estonia, Latvia and Ukraine to the Asian region. All of said systems are connected together by means of high-voltage direct current transmission (HVDC). Only islands such as Iceland, Malta and Cyprus have their own isolated network without connection to the European interconnected system.
The power grids of the North African countries of Morocco, Algeria, Tunisia and Western Sahara are technically coupled via an AC voltage connection between Spain and Morocco synchronously to the continental European grid.
The fact that the UK and the Nordic countries have their own ( non-synchronous ) interconnections, has its technical basis in the fact that three-phase alternating current greater performance can not be transmitted over the necessary long submarine cables. To direct current in the form of high-voltage direct current transmission (HVDC) must be used. Examples of such submarine cables are the HVDC conti- Skan HVDC Cross - Skagerrak, BritNed or NorNed.
A small, self- bonding system, which is used for historical reasons, with a grid frequency of 16.7 Hz exclusively for railway operation exists between the railroad networks in Germany, Austria and Switzerland. In other countries, the electric current for railway operation is taken directly from the general grid. This is possible because the local railways are powered by either direct current or alternating current of 50 Hz, which is to reshape with much less technical effort from the grid.
Properties
Each composite system is characterized in that it all producers as synchronous power plants, ie with identical grid frequency and corresponding phase able to work. This allows them to be connected directly electrically substations. If AC voltage at the frequency or phase position is not exactly the same for all producers, shorts would be the result. Although neighboring interconnections can be equipped with the same nominal mains frequency of 50 Hz, for example, by running small fluctuations in frequency are those concrete values but not identical, so no direct electrical network can be established.
Each composite system is divided into several zones. Germany for example, includes four control zones, Austria and Switzerland each have a control area, each with a transmission system operator, which occurs as a control area manager. The object of the control zone management, among other things, which kept available by the network operators control power to coordinate. The reason is that electric power grids, and interconnections, electrical energy can not save. It must at all times the electric power generated corresponding to the requested electrical consumption, otherwise the network frequency differs in the entire interconnected grid above (insufficient demand ) or down ( to high demand ).
These deviations are indicated on the transport network level by corresponding power flows in compensation and can lead in extreme cases to overloading of lines and transformers. Is it because a deviation that is less than certain tolerance thresholds above or this needs to be balanced in the context of network control and control power, whereby electrical energy can be exchanged for the purpose of balancing between the control areas. Thus, the reserved control power may be in a grid smaller than in small isolated networks. In 2010, about 3 GW of primary control power were held for example in the middle in the entire UCTE network, the frequency gradient of the control power is in the European interconnected system about 20 GW per Hz deviation of the grid frequency. If, because of deficits to a strong deviation of the grid frequency from the nominal frequency, such as in under-frequency, emergency measures to be taken, which may result in several independent sub-networks, in extreme cases, in addition to power outages to the temporary separation of the interconnected system.
The table below shows some key figures to the present in Europe interconnections are summarized:
Disorders
Even if a large-scale interconnected system exists, even major incidents can never be completely. The quality of care in the European interconnected system is compared to other interconnected systems high, as shown in the illustration on the curve of the mains frequency over 48 hours. Large Deviations of the mains frequency from the nominal value of 50 Hz downwards or upwards indicate larger differences in the balance of supply and demand. About more detailed analysis, such as whether the differences rather low-frequency components as in the Nordel interconnected grid or more high-frequency components as in UKTSOA - grid have to draw conclusions on the control properties of the respective composite network and the behavior in accidents can be drawn.
Examples of major disturbances in the UCTE interconnected system:
- On September 28, 2003 coincided almost the whole of Italy over sometimes more than 15 hours of electricity from. Even parts of France, Switzerland and Austria were briefly affected. The cause was a short circuit around 3 clock on the Lukmanier line in the area between Switzerland and Italy. Since not fast enough corresponding loads were taken from the grid within Italy, failed re- commissioning of the pipeline and in a chain reaction, all other interconnections between Italy and its neighbors were shut down due to overload. Italy, which is dependent on electricity imports, the state-owned power grid could no longer be maintained after separation from the European network. The reconstruction of the network took - staggered by region - 5-18 hours.
- When power failure on November 4, 2006 varied parts of the interconnected system in Western Europe for about 1 hour. The cause is related to a transient, occurred on schedule shutdown of a 400 kV high- voltage line across the Ems in Papenburg. This resulted in the further course in an overload of a plurality of connecting lines.
Possible future concept
As a European supergrid a fictional pan-European long-haul high-voltage grid is called. This could in particular for the exchange of fluctuating renewable energy over long distances. So it should help the regional weather conditions, different generation to compensate.
The term refers to a large-scale super grid transmission system, high-capacity, eg for the connection of offshore wind power in the North Sea to the riparian countries ( offshore grid).
Technically meshed high-voltage direct current transmission ( HVDC) High capacity with stand 2011 will not be realized, and are limited to within a few plants with simple taps on the end point connections between two converter stations. In the usual meshed AC systems based with three-phase high voltage transmission of the parameter is the node voltages also independent of the phase angle and thereby ties the parameters of the active power and reactive power. However, it was released in November 2012 one of the basic problems of HVDC: The company ABB has commissioned the development of a switch for high voltage direct current is known. This will be meshed HVDC realizable in the future.