Many terms are currently circulating in the media when discussing possible power interruptions. However, not all of them are easy to understand and often even incorrect. This can cause confusion. We will explain the differences here.
Load shedding: what does it mean?
Controlled load shedding refers to a deliberate power interruption that is limited to a certain region and time. Electricity consumers are temporarily taken off the grid to save electricity and restore the balance between generation and consumption. This balance, characterised by a stable frequency of 50 hertz, is the basic prerequisite for the overall smooth functioning of the power grid. This balance can be at risk when not enough electricity can be generated in Germany and the rest of Europe to cover the electricity demand. However, disturbances can occur if not enough line capacities are available to transport the electricity. In case of such grid congestion, conventional, i.e. including power plants using natural gas, need to help out to compensate for the electricity that is ‘stuck in the bottleneck’, so to speak. In case of a gas shortage, this too can become problematic and controlled load shedding may become necessary in the regions on the other side of the bottleneck when other, very extensive measures do not suffice either.
In both cases, the temporary disconnections are made without discrimination. The transmission system operators instruct the distribution system operators (DSOs) in the respective regions to save a certain amount of electricity for a very brief time. The DSOs carry out this instruction independently in their own regions and cut off individual streets, residential areas, municipalities or larger companies from the power supply until the total volume they were instructed to save is reached. In general, all households or companies in the grid area in question can be affected. In order to minimise encumbrances, the disconnections can be rotated depending on the duration of the power shortage, i.e. certain groups of consumers are supplied again, while others are cut off. In the scope of the second special analysis, the transmission system operators put forward the recommendation to make load reduction potentials in the industry usable for system stability purposes. In the past months, such a process was developed and aligned.
Large industrial consumers are now able, after appropriate registration for the process, to voluntarily make load reduction potentials available to avoid possible controlled load shedding or minimise its effects, e.g. damage to production lines and production waste. By participating in the process, large industrial consumers have the advantage that they can better anticipate imminent disconnections and adjust or plan their processes accordingly. In the event of a power shortage, this reduces the risk of controlled load shedding due to insufficient electricity production.
What is a blackout?
A blackout is a cross-regional, uncontrolled collapse of the electricity transmission grid. There can be many causes for a blackout, ranging from a sudden outage of several large generating units or damage to lines or substations as a result of natural catastrophes to criminal attacks on the IT infrastructure. A blackout is very unlikely; there has never been a large-scale, uncontrolled power outage in large parts of the European interconnected electricity system.