Administration of the transmission grid

TenneT administers the Dutch high‑voltage grid. We ensure the proper maintenance of our total infrastructure: substations and connections. We are aware of our responsibility towards society, the environment and its employees. That is why we not only handle the technology with care, but our environment and our people as well. 

Acceptable costs

Our maintenance strategy is aimed at minimising the risks (of a disruption in the energy supply, damage to the environment and safety incidents) at socially acceptable costs. After all, our customers expect to pay a reasonable price for a reliable energy supply. We therefore devote considerable attention to new methods and technologies in order to continually improve our maintenance.

Precautions

TenneT administers a high‑voltage grid of over 9,000 kilometres. We control this grid through about 267 stations. To guarantee the smooth technical operation of the transmission grid, TenneT takes precautionary measures: we perform inspections and preventive maintenance on substations, lines and cables. If faults nevertheless occur, we will carry out repair work. 

Substations

Transformers are located at the substations. TenneT uses these to transform electric power from one voltage to another. In this way we can connect a 380 kV line to a 220 kV line, for example, or transmit electricity to regional grid administrators. A transformer has an average useful life of several decades and is inspected regularly. Various other equipment is located in and around the transformer. This equipment, too, is inspected regularly. An example is the tap changer, a device similar to a dimmer switch, which we use to control the current and keep it at the required level. We also regularly check the location where the high‑voltage cable enters the transformer. 

High-voltage lines and pylons

High‑voltage lines require relatively little maintenance. They usually give decades of service. The high‑voltage pylons are easy to maintain as well, and can remain operational for up to 100 years. They merely need to be painted from time to time. According to the current maintenance plan, TenneT inspects connections once every 8 to 10 years. We select a pylon at random and inspect it thoroughly. Parts of the pylons that are sometimes replaced by TenneT are, for example, the insulator strings (which ensure there is sufficient space between the line, which is charged, and the mast, which may not be charged) and the spacers (which ensure there is sufficient space between the lines). 

We carry out helicopter flights each year to inspect the conductors, the suspension and the buildings near the high‑voltage lines. TenneT also maintains the green areas at the substations, around the pylons and along the high‑voltage lines. This is necessary, among other things, to ensure that plants and trees growing around the connections do not obstruct the energy supply.