The sky is getting dark, clouds are gathering: there’s a storm brewing. With lightning, thunder and gusts of wind. Switzerland was particularly affected by this natural phenomenon in July and August. Severe thunderstorms repeatedly swept across the country – with hail, strong or even gale-force winds, and lots of lightning.

The employees in the Swissgrid grid control rooms have to be especially attentive whenever thunderstorms are forecast. They monitor the Swiss transmission grid around the clock and ensure that electrical energy is transmitted smoothly at all times. How should they react if a line is struck by lightning? Or if a branch falls on a line? Let’s take a look at their work and the difficulties they face in the summer.

High production levels and large numbers of outages

The high temperatures experienced in the summer cause the glaciers to melt rapidly, filling the reservoirs of the hydroelectric power plants to the brim. This means that the power plants have to operate at full capacity, as all the energy produced has to be transported from the Alps to the major consumption regions, leading to heavily utilised lines.

This difficult situation is accentuated by outages. The best time to inspect power lines and electricity pylons is during the summer months. The lines have to be switched off to allow this work to be carried out. This decreases the line capacity available to transport electrical energy. As a result, the transmission system is more susceptible to disturbances and overloads in the summer.

An additional challenge: summer thunderstorms and lightning

Swissgrid employees must pay extra attention when thunderstorms occur in the summer. It is not at all uncommon for lightning to strike lines. In the summer of 2023, this was the case more than 50 times.

In the event of a lightning strike, the protection systems are activated immediately to switch off the affected line. Within one second, the line is then automatically switched on again. This rapid switching off and on of the line is called short-circuiting and is essential to prevent other lines from overloading.

The most important thing for employees to do is to keep calm! Every line outage must be thoroughly analysed and documented. The affected line is identified straight away with the help of the grid control system. At the same time, the employees check the precipitation radar, which is shown on a large screen in the grid control room, to assess whether the problem could have been caused by a lightning strike. Their initial suspicions are confirmed by a lightning detection system. The employees collect all the relevant data and have to inform a large number of partners about the disturbance within ten minutes.

Violent thunderstorms can cause branches or even whole trees to fall onto lines. The line cannot be switched back on automatically in this instance. The on-call service is immediately called out to carry out an on-site inspection. With the help of a distance protection system, the grid control room employees can rapidly identify the affected line section. As soon as the disturbance has been rectified, the line is switched back on manually by the specialists in the grid control room.

Looking to the future: digital solutions for greater efficiency

Swissgrid already uses tools that provide high-quality weather measurement data and forecasts in order to be as accurately informed as possible about future weather conditions. Swissgrid is also investing in the digitalisation of its system operation. The aim is to automate some of its processes and to use digital solutions for data-driven decision-making. This will help the employees in the grid control room to cope with the increasingly challenging situations in the grid.

The continuous further training of the specialists in the grid control room – in areas including disturbance and stress management – is another important pillar for increasing the safety of grid operations. In addition, simulator training is conducted annually to make sure that the team can overcome difficult situations.

Swissgrid is focusing on digitalisation not only in grid operations, but also in infrastructure management. A completely digitalised grid image – a digital twin of the physical grid – will provide the basis for establishing data-driven plant management in the future. This will allow the status of plants to be monitored more precisely over the entire life cycle and enable the grid to be operated in a more risk-based and efficient manner. It will become possible to shorten line outages and increase the availability of the grid, for example.