Germany has a well developed and intricately meshed electricity grid. The primary responsibility for operating the grids securely and for developing them to meet the demand rests with the grid operators. Their responsibilities are clearly defined in the (in German): the grid operators should ensure that the demand for electricity is met and should provide dependable grids to contribute to the reliability of the power supply in Germany.
The electricity grid in Germany is sub-divided into transmission grids (maximum voltage) and distribution grids (high, medium and low voltage).
Long-distance: the transmission grids
Transmission grids facilitate the transport of electricity over large distances throughout Germany and even across borders - with a minimum of loss, and directly to the areas where a lot of power is consumed. The German high voltage grid is linked to the wider European grid by interconnected lines. The total length of the German transmission grids is about 35,000 kilometres. In the case of alternating current (AC), electricity is transmitted with a maximum voltage of 220 kilovolts (kV) or 380 kV; the voltage of the planned new high voltage direct current (DC) transmission lines will be up to 525 kV.
he operators of these transmission grids are service companies which are responsible for operating the infrastructure of the supraregional electricity transmission grids, maintaining the grids, extending and modernising power cables and providing power resellers and suppliers with non-discriminatory access to these grids.
They also have the task of minimising grid fluctuations which arise from deviations between the volume of electricity generated and the demand. In Germany the high voltage transmission grid is largely owned by the four transmission system operators (TSOs): TenneT, 50Hertz Transmission, Amprion and TransnetBW.
Directly to the consumer: distribution grids
At the level of the distribution grids the electricity is transmitted at high, medium and low voltage.
- High voltage: 60 kV to 220 kV (grid length approx. 77,000 km)
The high voltage grid is used for the primary distribution of the electricity. Power is transmitted via the high voltage grid to transformer substations in population centres or large industrial companies.
- Medium voltage: 6 kV to 60 kV (grid length approx. 479,000 km)
The medium voltage grid distributes the electricity to regional transformer substations, or directly to large facilities such as hospitals or factories.
- Low voltage: 230 V or 400 V (grid length approx. 1,123,000 km)
The low voltage grid is used for fine distribution of the electricity. The low voltage grid serves private households, small industrial companies, commercial enterprises and office premises. Lower voltage grids distribute the power to end users. In this area there are a large number of regional and municipal grid operators.
Challenges facing the electricity grids
The demands placed on the electricity grids have become progressively higher. The growth in electricity trading, the increase in renewable energy and the resulting greater distance between where power is generated and where it is consumed have led to a rise in the volume of power transmitted and the fluctuations in the amount of electricity generated, entailing an extra load on the grids.
To ensure that these demands can continue to be met, major investments are needed in the . The key question is how the regulations must be shaped in future so that the grid operators can respond to the needs of the energy transition in their grids.
Throughout Europe the grids are faced with three major challenges:
- The share of power generated from fluctuating energy sources is increasing ("the wind doesn't blow all the time"): fluctuations can affect the stability of the grids. This applies both to the major long-distance high voltage lines through Germany ("transmission grids") and to the regional electricity lines ("distribution grids").
- A large number of power generation installations are being connected with the grid (e.g. rooftop photovoltaic installations, small wind farms): earlier, the electricity was transmitted in one direction only, from the transmission grids through the distribution grids to the end user. Today, the grids must also cope with transmission in the other direction, i.e. both "from top to bottom" and "from bottom to top".
- Electricity trading in the EU is increasing. Germany - as a transit country between the western and eastern European electricity markets - is likely to encounter significantly more cross-border electricity trading than other countries.
A report by the Federal Network Agency of 2015 evaluating and containing proposals on the future development of incentive regulation, the central instrument of grid system operator regulation, can be found (in German) . In March 2015, the Federal Ministry for Economic Affairs and Energy presented . The centrepiece of this is a revision of the Incentive Regulation Ordinance. By taking into account statements from the industries concerned by this Ordinance, as well as consumers and the German Länder, the Federal Ministry for Economic Affairs and Energy developed a draft amendment of the Incentive Regulation Ordinance, which was adopted by Cabinet on 1 June 2016. Prior to this, the Bundesrat had adopted several amendments to the Ordinance and subsequently approved it on 8 July 2016, thus paving the way for its final approval by the Federal Cabinet on .
In view of these challenges, power generation, the grid, transport and consumption must not be considered in isolation. A comprehensive view is necessary:
- New power lines: the distance between the places where electricity is generated and the places where it is used can only be covered with new power lines. Therefore the Energy Grid Expansion Act (Energieleitungsausbaugesetz, EnLAG) and the Grid Expansion Acceleration Act (Netzausbaubeschleunigungsgesetz, NABEG) were created with the aim of accelerating the construction of urgently needed power lines.
- European coordination: the German power grid is operated within the Continental European synchronous grid. The expansion of the grid also has to be coordinated. Currently, the European Commission is carrying out an EU-wide consultation on potential projects of common interest in the field of electricity and gas infrastructure. Authorities, companies, interest groups, environmental organisations and private individuals were able to have their say on the proposals until 22 October 2015. The consultation is available on the .
- "Smart grids": the grids, the power generation system and demand must be efficiently and smartly linked with each other. All parties must work together - the grid operators, the local planning and approving authorities and local citizen initiatives. Dialogue and cooperation are the only ways to create an awareness of the urgent necessity of grid expansion.
Underground cables for the transmission grid
Electricity can be transported both above and below the ground. At distribution grid level, underground powerlines are the norm in Germany. In contrast, the transport of electricity across large distances at high-voltage level, via the transmission grids, has generally taken place using overhead powerlines. Also, alternating current is mostly used. In future, high voltage direct current (HVDC) transmission is also to be used for the major north-south electricity highways (e.g. SuedLink).
The Federal Government has put the policies in place for expanding the grid more quickly and gaining public acceptance for it. Following the agreement within the governing coalition in July 2015, the cabinet (in German). On 3 December 2015, the Bundestag adopted the draft legislation, as amended by the coalition party groups, and the bill passed the Bundesrat on 18 December 2015. The new rules entered into force at the turn of the year 2015/2016.
In future, priority will be given to building the new electricity highways (the HVDC transmission lines) as underground rather than overhead powerlines. This applies in particular to the large transmission lines running from north to south such as 'SuedLink' or 'SuedOstLink'. In general, overhead DC powerlines are to be prohibited in places where people live. They will only be used in exceptional cases, for example in areas where nature conservation interests are identified or where existing powerlines can be used without major impact to the environment. Overhead powerlines may also be used if local authorities specifically request these powerlines in order to meet local needs.
The use of underground cables for AC projects, in contrast, is initially to be tested in the context of pilot projects in order to gather experience and advance their technological development. Germany - and indeed the whole of Europe - lacks experience with the use of underground high-voltage AC cables. The reason is that this new technology entails some technical challenges in the mesh AC network. These must be sorted out before wider use is made in order to avoid any problems with security of supply. The Federal Government is monitoring the progress being made on this technology. A pilot project at Raesfeld in North Rhine-Westphalia is currently gathering initial practical experience with underground cables. The pros and cons of this new technology are being evaluated along 3.5 km of cable. This by the Federal Network Agency (in German) explains more about the project.
The new rules are now also expanding the possibilities for underground AC powerlines to a moderate degree. In all of the pilot projects, underground cables can be used in sections where this is technically and economically efficient if the overhead line would fail to maintain a certain distance from residential buildings. The new rules also supplement the criteria for possible underground cables on all the pilot routes. What this means is that, in particular when required for nature conservation reasons, it will be possible in future to place the powerlines partially underground. .