Article - Grids and Grid Expansion

Electricity Grids of the Future


underground cable; Source: Bundesnetzagentur

© Bundesnetzagentur

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 Energy Industry Act (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 expansion and modernisation of electricity grids. 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) here. In March 2015, the Federal Ministry for Economic Affairs and Energy presented key points for "a modern regulatory framework for modern distribution grids". 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 3 August 2016.

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 website of the European Commission.
  • "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 gave the go-ahead in October 2015 for an increased use of underground DC cables (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 video 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. Also, additional AC pilot projects are envisaged in agreement with the Länder (in German) (PDF: 49,1 KB).

Grid expansion is an indispensable part of the energy transition

Well-developed grids make it possible to deliver electricity cost-efficiently. The energy transition is creating completely new challenges for the transport of electricity. The necessary expansion and restructuring of power grids is therefore an important aspect of the energy transition. This is because the power generation structure is changing. Increasingly, electricity is being generated by distributed wind and solar installations, some of them located a long way from the consumers. Not least, the electricity generated by wind turbines and new conventional power stations in the north of Germany has to be transported to the major power consumption regions in the west and south.

The aim of the Federal Ministry for Economic Affairs and Energy is to continue the rapid expansion and restructuring of the electricity grids and to dovetail this better with the expansion of renewable energy. The necessary measures for the expansion of the grid are being developed with public participation in a multi-stage process. In order to ascertain the demand, the transmission system operators elaborate a scenario framework by estimating the development in power generation and consumption - taking on board the Federal Government's medium- and long-term energy policy goals. This is then fed into the updates of the transmission system operators' grid development plans, which are scrutinised and confirmed by the Federal Network Agency.

Legal framework for the expansion of the grid

Four pieces of legislation form the basis for the coordinated, accelerated and transparent expansion of the grid: the Energy Industry Act (EnWG), the Grid Expansion Acceleration Act (NABEG), the Federal Requirement Plan Act (BBPlG) and the Power Grid Expansion Act (EnLAG).

Energy Industry Act (EnWG)
The Energy Industry Act ensures transparent and coordinated annual grid expansion planning for the German high voltage grid. The grid expansion requirement is determined in a multi-stage process.

Grid Expansion Acceleration Act (NABEG)
The Grid Expansion Acceleration Act simplifies the planning of grid expansion projects which involve several federal states or cross national boundaries: power line routes are centrally planned and approved by the Federal Network Agency in a process involving early public participation. In addition, the Federal Network Agency is responsible for the statutory planning approval procedure for grid expansion projects, which means it can define the precise route of the power lines. The transfer of the planning responsibility from state to federal level streamlines the process and avoids the fragmentation of tasks.

Federal Requirement Plan Act (BBPlG)
The Federal Requirement Plan continues to be the central instrument for the expansion of the transmission grids. It identifies the priority expansion projects on the basis of the Grid Development Plan and the Offshore Grid Development Plan.

Power Grid Expansion Act (EnLAG)
Alongside the Federal Requirement Plan Act, the Power Grid Expansion Act, dating from 2009, lists other priority projects which are exclusively the responsibility of the federal states.

The process: multi-stage and with public participation

A multi-stage process determines the extent to which the grid in Germany should be expanded, and which routes this expansion should apply to.

1. Scenarios for the power supply
How much electricity will we consume in the next few years, and where? What role will conventional power stations and renewable energy sources play in future? A "scenario framework" answers these questions and thus provides the basis for the necessary grid expansion planning. This scenario framework is prepared by the transmission system operators and approved by the Federal Network Agency.

The Federal Network Agency's website contains the approved and draft scenario frameworks - sorted by target year.

2. Grid development plan and environmental report
On the basis of the scenario plans, the transmission system operators prepare an annual draft grid development plan, which is opened up to public consultation. Once the public consultation has been concluded, the transmission system operators revise the draft, which is then presented to the Federal Network Agency for scrutiny and confirmation. The Federal Network Agency then draws up an environmental report for the confirmed grid development plan. This process was first carried out in 2012 (for target year 2022). In November 2012 the Federal Network Agency handed the first national grid development plan and the environmental impact report to the Federal Ministry for Economic Affairs and Energy (for target year 2022).

In 2013, the transmission system operators produced not only the draft grid development plan (for target year 2023), but also an offshore grid development plan for the power lines connecting the offshore wind turbines. Since then, the offshore grid development plan has formed part of the process described here.

The Federal Network Agency's website contains the approved or draft grid development plans and offshore grid development plans, as well as the environmental reports - sorted by target year.

3. Federal Requirement Plan
The Federal Requirement Plan is compiled on the basis of the grid development plans. In this process, the projects cited in the Power Grid Expansion Act (the "start network") are regarded as predefined. The Federal Requirement Plan Act then defines which additional grid development projects are necessary for the energy sector and are deemed a priority. The Federal Requirement Plan Act is updated at least every three years.

4. Decision on power line routing
The Federal Requirement Plan only defines the starting and finishing point of identified projects; there is also a need to decide on the route corridor. There are clearly defined responsibilities for the selection of corridors for grid expansion: if the planned power lines cross state or international boundaries, the Federal Network Agency decides on the selection of the corridors (federal planning). Decisions about power line routes within one federal state are made by that federal state.

5. Defining the exact power line routes in the statutory planning approval procedure
The corridors identified in the fourth stage form the basis for the statutory planning approval procedure. The transmission system operators must initially consider several alternative routes for each corridor. Their suggestions are publicly discussed and checked for environmental compatibility. The process ends with the official planning approval which defines the exact power line routes which are deemed to create the least impact for people and the environment.

Public participation

In the expansion of the power grids, the Federal Ministry for Economic Affairs and Energy aims for comprehensive information and early dialogue with the affected citizens. The grid expansion can only be successfully carried out if there is high acceptance of the planned projects. For this reason, the Federal Network Agency ensures early and comprehensive public participation in all the stages of the process to expand the grid.
Learn more about the citizens' dialogue.

Further information

Connecting offshore wind energy to the grid; Source: Beselt

© Beselt

In addition to onshore wind energy, the use of offshore wind energy is another key element of the German government's energy and climate policy. Thanks to the constant and reliably high wind speeds at sea, offshore wind energy has an important role to play in the energy transition.

In Germany, suitable sites for the use of offshore wind energy are mainly to be found in the "exclusive economic zone", i.e. beyond the 12 nautical mile zone and, compared with other countries, well away from the coast. This gives consideration to the various other uses of the North and Baltic Seas, especially nature conservation, such as protection of the Wattenmeer world natural heritage site, or shipping and fisheries.

Offshore grid connections are needed to transport the wind energy generated in the North and Baltic Seas to the consumers. These connections link up the offshore wind energy installations with onshore connection points, from where the electricity is transported via the onshore grid. Due to the distance of the offshore wind energy installations from the coast, the grid connection is a technical, financial and logistical challenge. There is thus a need for close coordination between the design of a wind farm and the related grid connection so that the work can be synchronised and the financial risks minimised. Alternating current is used to transport the electricity generated by the Baltic wind farms. Due to the significantly greater distances in the North Sea, high-voltage direct current (HVDC) transmission lines of up to 320 kV are mainly used there.

The question of which offshore connection lines are to be constructed in the coming years is answered every two years in the offshore grid development plan, which the Federal Network Agency generally confirms in tandem with the onshore grid development plan. On this basis, the transmission system operators responsible for building the connection then undertake the necessary work.

Further information