Peak capping

Peak capping describes the curtailment of feed-in peaks from onshore wind farms and photovoltaic systems as part of grid planning. It is a planning tool used for dimensioning the grid and does not denote any actual intervention in the energy feed-in (see feed-in management). This makes it possible to avoid expanding the grid merely to cater to rarely occurring peaks in energy feed-in.

Peak load

The peak load is the maximum output that can be withdrawn by a consumption device or procured through the supply network during a given period of time (e.g. day, month, year).

Phase-shifting transformer (PST)

A phase-shifting transformer is an element used for active control of the power flow in the AC grid, making it a measure for grid optimisation in accordance with the NOVA principle. Phase-shifting transformers serve to optimise the capacity utilisation of the existing grid via cross-compensation to make use of available capacities in existing AC lines.

Point measures

In addition to power line construction measures, so-called “point measures” are also required as part of the Network Development Plan (NDP). These include transformers, reactive power compensation facilities and substations. A distinction is drawn between vertical point measures, which are identified in the NDP in consultation with the distribution system operators, and horizontal point measures, which concern the extra-high voltage grid exclusively.

Power plant

A power plant is a facility that has been designed to convert energy from a primary or secondary energy source to produce electrical energy.

Power plant operator

Either through ownership or contract, a power plant operator possesses the capacity of a power plant and can determine how it is used.

Power-frequency control

The term power-frequency control refers to a regulating process used by the TSOs so that they can adhere to the agreed upon quantities of electricity at the borders of their control areas in times of normal operation and particularly in the event of any system failure. Each TSO strives to manage the contribution of its own control area so as to keep the exchange of power with other control areas within the agreed limits as well as to ensure that the grid frequency stays as close to the set value as possible. Power-frequency control consists of primary and secondary control.

Primary control
Primary energy

Energy that is available from naturally occurring energy types or sources, for example, coal, gas or wind. This differs from secondary energy, which is only made available through the conversion of primary energy.

Project of Common Interest (PCI)

In 2013, the European Commission published a list of projects of European importance entitled Projects of Common Interest (PCI). This list includes around 100 electricity transmission projects throughout Europe. Implementing Projects of Common Interest is to be given top priority. The criteria for selecting a project were: it provides a substantial benefit to at least two EU member states, it helps to strengthen the European single market, it increases the security of supply and it reduces CO2 emissions.You can find out more about PCI projects on the European Commission’s website here: