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Society relies on us to provide a reliable and uninterrupted supply of electricity. Our high-voltage grid plays an integral part in the daily lives of 41 million end-users throughout the Netherlands and large parts of Germany. Major investment projects are needed to ensure the best possible performance and reliability of our grid and its ability to handle the large amount of renewable energy being fed into it. To make sure these projects happen, we are working with society at both a national and a local level. We try to be as open and transparent as possible, helping people understand what we are doing so as to gain their acceptance for our strategy and projects.

InputStrategic prioritiesChallengesOutput
Need for reliable electricity supplyEnhance the flexibility and resilience of our transmission grid to ensure security of supplyIncreasingly complex environmentGrid availability of 99.9999%
Asset InfrastructureRedispatch measures and related costs are risingCircuit length of 22,573 km
Anticipate and address what society wants and needs through dialogue and innovationExpectations on underground cabling171 information meetings
Our work is crucial yet often invisible


Grid availability

We maintained a high reliability level throughout 2016, despite the ongoing demand for more electricity. We dealt with the challenges created by the high load of renewable energy being fed into our grid and demonstrated our ability to handle these high flows, adapting to the changing supply side of today’s energy market, while meeting the same high level of consumer demand. In early January, a rare phenomenon called ‘line galloping’ occurred in the north of the Netherlands. This happens when specific temperature, humidity and wind conditions combine, causing ice to form on power lines. This ice makes the power lines more wind resistant, which in turns makes them move more. Although this phenomenon caused some voltage dips in our network, there were no outages and our grid availability remained at a constant high level. Our onshore grid availability in 2015 was 99.9975% due to a power outage on the 380 kV substation in Diemen on 27 March 2015.

Grid availability99.9999%99.9975%99.9999%
Energy not transported (MWh)593,82477
Grid availability92.00%92.82%N/A

For more information about our grid availability performance per voltage level and country, click here.

Our offshore grid availability was 92%. This availability figure cannot be compared one on one with our onshore grid availability because our offshore grid is designed with no redundancy. This means that maintenance always leads to unavailability and 100% grid availability is not possible. Unavailability last year was due to maintenance. Our offshore connection DolWin2 encountered technical difficulties with the sea and land cables. We analysed the issue together with the supplier and the connection was put back into operational again by the beginning of 2017, starting with extensive test procedures. The Riffgat connection was put back into operation in May, after succesful repair of the cable in no more than six months downtime.
For more information about our forecasts on security of supply in the Netherlands, click here. For more information about our forecasts on security of supply in Germany, click here.

Societal costs

The increased challenges in operating our grid have an effect on the costs society pays. The majority of increased network charges are due to ‘network stabilising emergency’ actions, which are caused by the transmission grid being placed under more supply pressure. As such, any delays in the construction of new power grids may cost substantially more than the actual construction of new towers and lines. The expenses associated with these actions are reimbursed via regulatory tariffs (see the financial section of this report). For more specific information about our revenue, costs and profit, click here.

Connecting citizens

As we continue to invest to ensure our grid can handle the incoming electricity flows now and in the future, our asset base also continues to grow. Our circuit length increased from 22,245 km in 2015 to 22,573 km last year.

Total circuit length (km)22,57322,24520,858
Overhead lines (km)18,82918,89318,716
Underground cabling (km)3,7443,3522,142
Number of substations454454443
HVDC Converter locations15133

For detailed information on our infrastructure per voltage level and country, click here.

Several new projects came into operation in 2016, including a 43 km underground cable in the Netherlands and the 16 km-long Brunsbüttel - Süderdonn connection of the Westküstenleitung in Germany. The overhead lines circuit length decreased in 2016, mainly due to decommissioning of lines at the Hoogeveen-Veenoord connection related to a route change.

Our German offshore capacity is now 5,221 MW, operated by eight convertor systems, which is more than enough to transport the entire currently installed windfarm capacity of 3,783 MW.

To encourage dialogue about acceptance, costs, technological innovations and the future of energy sources, we asked external parties to perform a stress test on the planning for the current German grid expansion. This test analysed whether alternative development paths of energy supply and demand and developments in planning and operations could significantly alter the structure of the expansion of the high-voltage grid after 2030. The test found that the current grid projects defined by law are necessary to achieve the renewables energy goals in Germany for the time being, but that the further growing supply of renewable energy and the resulting increase in transportation requirements can be solved after 2030 with a significantly lower grid expansion.

From 33 kV to 66 kV for Dutch wind farms

Transmission capacity of the cables connecting wind farms to offshore platforms is directly linked to voltage levels. Traditionally, 33 kilovolt (kV) is the voltage level used for this – a proven technology applied in almost all wind farms. As the capacity of turbines grows and offshore wind farms get larger, developers are eying higher voltage levels, but the step has not yet been taken. The next logical step is widely seen as 66 kV, which increases the number of wind turbines that can be connected to one single inter-array cable, reducing the number and overall length of cables necessary. Encouraged by our offshore experiences in Germany, TenneT took the lead in conducting a study concluding that 66 kV voltage levels for Dutch wind farms would reduce the Levelized Cost of Energy (LCoE) by 1.1 to 1.3% in the first instance, paving the way for further innovations and even lower LCoE in future tenders. For Dutch wind farms, this will become the norm going forward.

Community engagement

We made significant strides last year in how we interact with the public, keeping stakeholders and local communities informed about our plans and strategies. This dialogue is particularly crucial in Germany, where grid expansion has a substantial impact and local communities are very vocal on energy matters.

We continue to hold an open and transparent public dialogue on the SuedLink and SuedOstLink in Germany, as well as on our alternating current (AC) grid projects. We also continue to encourage engagement on connecting offshore wind to the onshore grid in the Netherlands. Last year, we held 83 public meetings in the Netherlands and 88 in Germany. In Germany, high-capacity power lines such as the 800 km north-south SuedLink line play a decisive role in achieving energy transition. The German parliament has decreed that underground cabling is the way forward for direct current (DC) projects. As such, we have re-evaluated our plans for the SuedLink, which will now be entirely underground, thereby creating the longest high-voltage underground line ever.

"We have integrally planned the SuedLink project as underground cable. Citizens have prompted and politicians paved the way for underground cabling”
Lex Hartman, Director Corporate Development TenneT

We are working on new power line corridors and presenting them to the public. We hosted 35 community workshops across Germany to help plan the best routes, and our efforts have been widely recognised. Our experience in Germany with many cutting-edge technologies such as underground cabling is also beneficial in the Netherlands. For example, we led the discussion on how best to incorporate offshore wind energy into the onshore Dutch grid. To step up our approach towards stakeholders in the Netherlands, we worked together with knowledge partners to help understand the facts of the matter as well as the feelings surrounding it. We have used these insights to improve the way we communicate during public consultation meetings.

"In our capacity as state government, we have initiated the dialogue process in consultation with TenneT – not only to explain to the population why we need lines, but also in order to engage with critical questions, recognise conflicts at an early stage, and find solutions. Our cooperation with TenneT has been highly successful in this respect, albeit not always without conflict."
Dr Robert Habeck, Minister of Energy, Agriculture, the Environment and Rural Areas Schleswig-Holstein

Our challenges in society

1The environment in which we operate is becoming increasingly complex. Not only are we adapting to a fast-changing market where renewables are flooding into a system originally built for fossil fuels, but we are also doing business in a world facing more IT-related risks, cyber security issues and even potential terror attacks.We adapted our strategy "Enabling the Change" last year. Seven strategic priorities, see the section "About TenneT-Our Strategy", serve as building blocks in our response to the changing market environment.
2The expectations on underground cabling represent another challenge, with the related cost and potential technical difficulties not immediately understood and in need of explaining.Stepping up our stakeholder dialogue by explaining that underground cabling is at least 3-8 times more expensive than traditional overhead lines and that not all lines are suitable for underground construction. The length of the cable is also crucial: the longer it is, the more technological challenges there are.
3As grid operator, our work is crucial yet often invisible. Combined with our responsibility for balancing the grid, this places us under increased scrutiny, with the possibility of misunderstanding.In our view, stakeholder management is key to achieving societal acceptance. This means we explain the consequences of alternative solutions in a transparent way to all relevant stakeholders at an early stage to facilitate the public discussion and to acquire full validation of our projects from the authorities to create value for society and stakeholders.
4Redispatch measures – rising steeply in Germany and the Netherlands due to the inflow of renewables and the growth of international flows – can at times conflict with our long-standing priority of ensuring adequate supply.We have been discussing changes in the market mechanisms, including the addition of renewable energy facilities to redispatch and the introduction of a coordinated process for the determination of capacities in Central Eastern Europe. Furthermore, we aim to complete grid expansion projects as quickly as possible.

Looking ahead

Our absolute priority is to ensure that our 41 million end-users have a secure supply of energy. With 29 projects underway in Germany and work required in the Netherlands to upgrade the grid over the next 10-15 years, we continue to invest in our grid to cope with future demand. Our 10-year investment portfolio, with an expected volume of EUR 25 billion, must be executed effectively and efficiently, on time and on budget, implementing technological improvements along the way. We will involve our stakeholders at the earliest stage of our projects, by holding information meetings to gain acceptance of our construction activities.

We are leading the way in terms of underground cabling in Europe and have already laid 1,500 km of DC cable underground. This trend is likely to continue and we plan to build on our expertise. Other technologies we are working on include lightweight plastic insulated cables and the use of 525 kV instead of 380 kV cables. These can transport similar quantities of power over fewer cables, making them cheaper and allowing for less intrusive installation procedures.

True value - a case study of cabling in Apeldoorn

Being transparent about our impact on society is crucial in our dialogue with stakeholders. Although difficult, we see the value in being able to compare the different impact we have. As such, we have made a first step in monetising our non-financial impact to provide insight into a project’s true societal impact. This approach is new in the industry and the outcome of this specific case should not be taken as an absolute truth, but as an indication of the most material impacts. In the selected pilot project in Apeldoorn, we installed underground cabling in the municipality to replace an overhead line that crossed two neighbourhoods and a park. Our research focused on finding out what the measurable social and ecological impact of this project would be compared to the existing situation. All the steps in the cabling value chain were taken into account, i.e. raw material extraction and production, the removal of existing lines and cabling, the operation of the high-voltage connection and end of life.

In each step of the value chain, the financial, social and ecological impact was determined based on the most material aspects, like investment costs, carbon footprint and living environment. The activities for each of these aspects were then translated into euros, which resulted in positive and negative social, ecological and financial volumes.

The results of our research showed that the improvement of the living environment had by far the most impact on social value, as illustrated in the chart below. For the ecological impact, carbon footprint, material depletion and biodiversity were taken into account. Since the surroundings did not change significantly, effects on biodiversity were minor. Financial costs consist of investment and maintenance costs, while the financial benefits relate to lower operational costs and increased value for the area around the high-voltage connection. For more information on the assumptions and conversion factors, click here.