The 49.5 hertz problem relates to challenges in the stability of the electricity grid, particularly in Germany and other countries with a well-developed grid for renewable energies. It is directly related to frequency regulation in the electricity grid.

Background
In a stable electricity grid in Europe, the frequency must be exactly 50 Hertz. However, this frequency can fluctuate depending on whether more electricity is generated than is consumed or vice versa. When there is overproduction, the frequency rises; when there is underproduction, it falls. A frequency that is too high or too low can destabilise the grid and, in extreme cases, lead to widespread power outages.

The 49.5 hertz limit
If the grid frequency falls below 49.5 hertz, this means that there is a significant shortage of electricity in the grid. In order to stabilise the grid, various protective mechanisms are automatically activated in this case. One measure is to switch off consumers that are participating in the so-called "immediate shutdown programme". These are often large industrial plants that can reduce their electricity consumption at short notice in order to stabilise the grid.

The problem
Due to the increased use of renewable energies such as wind and solar energy, which do not provide a continuous and predictable supply of electricity, fluctuations in the grid occur more frequently. If a large amount of electricity suddenly fails (e.g. in the event of a sudden drop in wind) or the consumption load changes significantly, the frequency can fall below the 49.5 Hertz limit. As the conventional, controllable power plants are partially reduced or switched off in the case of renewable energies, their stabilising properties are missing, which exacerbates the problem.

Interaction with neighbouring European countries is also important, as the European interconnected grid is closely linked. A drop in frequency in Germany can therefore have an impact on other countries.

Measures for avoidance
Various measures are being taken to avoid the 49.5 Hertz problem:

• Making electricity consumption more flexible: industrial customers and also private households can be given incentives to adapt their electricity consumption to the current grid situation.
• Storage systems: Battery storage or pumped storage power plants can feed energy into the grid or take it off at short notice when required.
• Intelligent grids: With the help of smart grids, the grid is better monitored and controlled in order to recognise and counteract fluctuations at an early stage.
• Grid expansion: The expansion of the transmission grid is intended to prevent bottlenecks and improve energy distribution.
  

The 49.5 Hertz problem is therefore an example of the challenges associated with the energy transition and the integration of renewable energies.