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Under high voltage

High-voltage pylons with wind turbines

For the energy transition to succeed, the networks for transmitting electricity must be massively expanded - this is also extremely important for the growth of Prokon.

High-voltage pylons with wind turbines

A milestone: The Federal Network Agency has presented its new roadmap for expanding the electricity transmission grid. According to this plan, on land, five new so-called power highways are planned, high-voltage direct current connections with a capacity of two gigawatts each. Three of them are intended to run in a north-south direction and two in an east-west direction. Additional lines are also planned to connect offshore wind farms.

The goal is to transport climate-neutral electricity to wherever it is needed, especially from the electricity-rich north to the south. According to Klaus Müller, President of the Federal Network Agency, the grid development plan shows for the first time which electricity grid Germany needs to complete the energy transition. The plan followed a months-long process where all interest groups and the public had the opportunity to express their opinions. Müller said that all four projects proposed by the transmission system operators had been carefully examined. The grid development plan does not yet define the exact routes, only the starting and ending points of the lines.

Fall behind

However, the Federal Audit Office immediately poured water into the wine. "The Federal Government is lagging behind in expanding renewable energies and the electricity grids, as well as in developing backup capacities," criticises its president Kay Scheller.

According to a recent study, the grid expansion is seven years behind schedule, including the necessity to transport wind power mainly from north to south. This occurs against the backdrop of a roughly one-third increase in electricity demand by 2030.

However, the issue is not only with the major 220 and 380 kV lines, but also with the connection to the 110 kV network in many cases. "It used to be taken for granted that network operators would allocate a grid connection to a wind or PV park and could take up the energy quantities," reports Prokon board member Henning von Stechow. "But now it is clear that the expansion of generation and the expansion of the grids are not happening in parallel." For von Stechow, grid expansion is therefore "one of the major topics in the coming years."

Delayed Connection

Two current examples from Prokon underline the drama of the situation:

As part of a repowering project, in the oldest Prokon wind park in Horst, Schleswig-Holstein, eight turbines with a total of 10.4 MW are being replaced by four more powerful turbines with 28 MW. The problem: The grid operator only allows a feed-in capacity of 22 MW. Grid expansion is not expected until 2032. One potential solution could be the construction of a Prokon-owned substation (page 20). However, this comes with significant additional costs and would impact the park's profitability.
In the Quarnstedt-Störkathen wind park, the repowering permit was granted in a record-breaking seven months. The four new turbines also total 28 MW and replace nine older ones with only 11.7 MW. The grid operator's 110 kV line is not expected to be ready until at least mid-2027. Until then, the grid can only handle around 14 MW. "We may need to throttle the new wind park and only feed in half the power," says von Stechow. When it comes to planning certainty, things are also precarious: Prokon had to deal with the grid operator changing the connection point at the last minute for its first photovoltaic open-space project in Walshausen. The consequence is that Prokon now needs to plan and build a 12.5-kilometre line to the new connection point. Until then, the park won't feed any power into the grid – the particularly innovative project with battery storage is put on hold for now.

Binding commitment demanded

For electricity producers, it is more than inconvenient that they usually only receive assurances from grid operators regarding performance and distances of grid connection points after receiving planning permission or approval under the Federal Immission Control Act (BImSchG). "Extensive planning, assessments and approval processes with corresponding costs have already been carried out - and a postponement of construction is hardly an option," explains von Stechow.

In order to achieve the ambitious goal of doubling the amount of energy generated from their own facilities, Prokon must be able to rely on powerful and flexible partners in the network sector. Therefore, the energy cooperative supports the call of industry experts such as the German Wind Energy Association (BWE) to synchronise grid expansion and the expansion of renewables, align planning and approval processes with the binding grid connection commitments, and promote the expansion of storage. "Grid expansion must have top priority on the economic and energy policy agenda," von Stechow demands. Only in this way can the energy transition succeed, for which Prokon and its members are committed sustainably and successfully.

Transmission network

The four players

The company 50Hertz Transmission GmbH operates the extra-high voltage electricity grid (220 kV and 380 kV) in eastern Germany including Berlin and in the Hamburg area with a total length of around 10,500 km.

Tennet TSO GmbH, based in Bayreuth, operates an extra-high voltage electricity grid (220 kV and 380 kV) in Germany between Schleswig-Holstein and Bavaria with a total length of around 13,559 km.

Amprion GmbH, based in Dortmund, operates the second largest extra-high voltage electricity grid in Germany with a circuit length of nearly 11,000 km.

TransnetBW GmbH operates in Baden-Württemberg and has 3,111 km of 220 kV and 380 kV circuits.

A map with the regions of the four grid operators in Germany

Five new 'electricity highways'

The plan includes five new high-voltage transmission connections, each with a capacity of two GW (dashed).

DC32 from Schleswig-Holstein to Mecklenburg-Vorpommern
DC35 from Lower Saxony to Hesse, DC40 from Lower Saxony to Saxony
DC41 from Lower Saxony to Baden-Württemberg
DC42 from Schleswig-Holstein to Baden-Württemberg

The exact routes of the planned connections have not yet been determined.

This is how the electricity is distributed in Germany:

From 380 kilovolts to 230 volts

The power grids are divided into several voltage levels based on different nominal voltages. These levels are often interconnected, usually through transformers.

Transmission network:

High voltage with 220-380 kV (circuit length approximately 37,000 km)

Transmission grids enable the nationwide and cross-border transport of electricity over long distances – as low-loss as possible and directly to where the electricity is consumed. Via so-called coupling lines, the German high-voltage grid is connected to the European interconnected network. Transmission takes place in three-phase (alternating current) at a maximum of 220 kilovolts (kV) or 380 kV, and in the planned new high-voltage direct current transmission lines at up to 525 kV.

Graphic production large power stations

Interregional distribution networks:

High voltage with 60 kV–220 kV (circuit length around 94,000 km)

The high-voltage network is the connection to the extra-high-voltage network (substations). High-voltage networks are used to distribute electricity broadly to urban areas or directly to large industrial plants. Wind farms are also connected via the typical 110 kV network.

Production and Acceptance of medium-sized power stations

Regional distribution grids:

Medium voltage with 6 kV–60 kV (circuit length approximately 520,000 km)

The medium-voltage grid distributes electricity to regional transformer stations or directly to larger facilities such as hospitals or factories.

Small power stations production

Local Distribution Networks:

Low voltage with 230 V or 400 V (circuit length around 1,190,000 km)

The low-voltage network is used for fine power distribution. Private households, small industrial plants, commercial enterprises and administration are connected to the low-voltage network.

Small power stations for low voltage

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