For the secure and reliable operation of the electricity supply system, precise coordination of all operational actions in the grid is required in accordance with the conditions of the transmission system and the connected power plants as well as the vertically or horizontally adjacent or connected grids in real-time. Overloads and blackouts have to be avoided and disturbances have to be controlled in a secure manner to quickly restore the secure state of the system.
To this end, the corresponding rules have to be applied at all times.
At all times, the transmission grid needs to be operated in such a way that the outage of an electrical connection such as an overhead line between two nodes (usually substations) does not lead to an outage of the electric power supply.
This can be ensured through a coordinated operation mode or combination of the many elements of the transmission system. Important elements of the transmission grid are lines or cables as well as transformers. System management for example has the responsibility to manage the grid in such a way that the load flow is ensured without limitations despite the outage of a connection.
If these measures do not suffice, system control can also directly influence the load flows by reducing the output of power plants or feed-in units in one grid area and increase the output in corresponding other Areas.If these measures do not suffice, system control can also directly influence the load flows by reducing the output of power plants or feed-in units in one grid area and increase the output in corresponding other areas.
An important element of secure system control is of course the secure and fast application of knowledge and skills in different grid situations. To ensure that these competences are always up to date, permanent further training and instruction of the daily operating personnel is necessary. The training and instruction concepts for instance focus on newly deployed grid elements and their behavior in the electrical energy supply grid, additionally connected customers and their installations, the evaluation of disturbances and critical grid situations and finally also the applicable legal framework conditions for discrimination-free grid access.
Controlling the technical failure of grid elements, which can unfortunately not always be avoided, as well as their effects on the surrounding grid area, is also part of system control. It is very important to predefine the right tools and their settings, so that corresponding protection systems and automatisms quickly and securely disconnect the failing grid elements from the grid with the necessary selectivity.
System management must also ensure that in case of a blackout, the supply is restored quickly, securely and above all, in coordination with the many partners in the electrical energy supply system. These situations therefore need to be considered in advance and the corresponding operational sequences have to be written down as concepts and trained.
A prerequisite for secure cooperation in the electrical energy supply system across the different grids are clear regulations for the industrial relations at the relevant grid interfaces, to be agreed upon with the corresponding partners, such as distribution system operators, conventional power plants, wind farms and industrial customers (e.g. steel mills). These rules and guidelines are developed together with the partners, laid down in system control agreements and continuously adjusted to the evolving grid development and other framework conditions. In addition, the grid and system control contracts concluded with neighboring transmission system operators and especially their extensive contract annexes with their technical descriptions and operating instructions are constantly updated as well, taking into account the changing conditions, both with regard to the state of grid development and the European and national legal provisions.
The constant evaluation and analysis of the system state in terms of voltage control and the connected reactive power demand is also an important task of system control. Particularly the observance of the fixed voltage limits has to be monitored. The findings from the evaluations and analyses are integrated in the operating instructions and/or form the basis for the determination of other requirements for elements of voltage and reactive power management, also in cooperation with the neighboring system operators, so that the voltage limits can also be observed in the future or proactively.