Glossary

Reactive power is the electrical power that is required to support magnetic (e.g. in motors and transformers) or electrical fields (e.g. in capacitors), but cannot be used to do work like real (or active) power.

To maintain voltage stability in the transmission grid, it is necessary to provide reactive power via facilities for reactive power compensation in addition to the generation units.

Real or active power describes the share of the apparent power that can actually be utilised.

Redispatch management is a request by the system operator to adjust the active power feed-in of power plants with the aim of preventing or eliminating n-1 violations. This measure can be used within a control area or across control areas. Power plant units are switched off before the bottleneck, while power plant units are restarted to the same extent after the bottleneck. Preventive redispatching is used in operational planning, e.g. to prevent n-1 violations within the next few hours. Curative redispatching refers to pre-planned temporary adjustments to eliminate existing or impending overloads in grid operation. Such measures take effect within certain time windows, taking into account the thermal capacities of the operating resources. They help to temporarily reduce the scope of preventive redispatch management, but are no substitute for the fundamental elimination of permanent bottlenecks through grid expansion.

The reliability of supply is the ability of an electricity supply system to fulfil its duties of supply under prescribed conditions and during a given time.

The newer generation of wind energy plants yield an output of up to 8 MW. These facilities are also more reliable, quieter and more efficient. The on-site replacement of older wind power stations for newer ones is therefore called repowering.