When load shedding in the power grid is called the shutdown of load ( consumables). The shutdown is because it generally represents an unplanned event, triggered by automatic means, such as the power protection upon achievement of certain pre-set measurements and carried out in automatic processes by opening circuit breakers in substations. For those affected by load shedding parts of the network and the connected consumer, this measure leads to a power failure.
In special cases, for example in the framework of the resynchronization of single, larger network segments, load shedding can also be triggered manually by the control centers.
A load shedding is the last possible measure to forestall the impending total collapse of an interconnected system or part thereof and is designed to stabilize remaining network segments. The rules for load shedding shall be determined by the respective regional network operators. In Germany, these rules are set out in the Network and System Rules of the German Transmission System Operators of the Association of Network Operators (VDN ).
Criteria and reasons for load shedding are:
- Undervoltage as a result of overloading the regional energy network
- Thermal overload of resources such as lines or transformers
Some large consumers, mainly cement mills or large cold stores, have as part of the load control contracts as " load shedding customers." Receive a reduced power requirement and must be set to the energy company and automatically within defined periods, typically in the range of seconds off.
While the load shedding effect in a stream network initially directly to the consumer in the form of regional power outages, it can also lead to repercussions on producers and a powerful factory load shedding by the lack of consumers.