DC (overlay) grid

A DC overlay grid is a linked system structure designed with HVDC technology that is overlaid on top of the existing AC grid infrastructure – meaning both the AC transmission grid and the AC distribution grid. It is designed to transport large quantities of energy over hundreds of kilometres and to manage energy flows much more flexibly over large regions than is possible in the AC grid. DC overlay grids are suitable for integrating large quantities of energy fed in from distributed renewable sources, such as from offshore wind farms, into the grid infrastructure without locally overloading the existing AC transmission grid (e.g. in coastal regions). The use of DC overlay grids makes it possible to economically create transport routes with high technical performance that allow redundancies to be shifted from the AC grid into the DC grid.

DC grid connection system
Direct current

Direct current indicates a flow of electrical current whose amount and direction is constant. In the literature, as in the GDP, the abbreviation ‘DC’ is commonly used.

Distribution grid

The distribution grid is used within a confined region for the distribution of electrical energy to supply facilities and consumer installations. The power flow throughout a distribution grid is primarily dictated by the consumer load. In Germany, low voltage grids, medium voltage grids and portions of the high voltage grid are used as distribution grids. See also transmission grid.

Distribution system operators (DSOs)

Operators of electricity distribution networks are natural persons, legal entities or legally dependent organisational units of an energy supply company, who are tasked with the distribution of electricity and are responsible for the safe and reliable operation, maintenance and any necessary expansion of the distribution network at the low-voltage, medium-high voltage or high-voltage level in a defined area as well as the connection lines to other networks where necessary.

Dumped Power

Dumped power, non-usable power, is the result of excess supply of power on the energy market. The total sum of dumped power over the year is known as ‘dumped energy’. The surplus power in a market area is the result of the sum of energy infeed, which cannot be reduced in spite of low energy prices (must-run generation, e.g. conventional combined heat and power or renewable energy infeed) minus the current load (including network losses) in the respective area. If this excess power cannot be stored or exported, the amount of power fed into the system must be reduced. In the model used in the GDP the infeed of energy from renewable sources is then reduced in addition to peak capping. Other options to reduce the amount of dumped energy is a reduction of conventional infeed, an increase in load, or the expansion of storage and export capacities.