Grid Types; Power Grid - Siemens SINAMICS S120 System Manual

Grid types

3.1

Power grid

A power grid covers a wide area, is generally supraregional and comprises large power
generating units (regarding the electric power). It is operated by a power supply utility, which
is responsible for the grid, and therefore also grid codes.
Generating units, which feed into a power grid must synchronize their voltage and frequency
to that of the power grid.
Figure 3-1 Schematic diagram of a power generating system connected to a power grid
Requirements
Every power grid operator has defined conditions when it comes to feeding in electrical
energy. The precise limit values can vary between different countries, and are defined in the
form of grid codes. As a consequence, they must be considered on a system-for-system
basis.
For example, in Germany this is the "Federal Association of Energy and Water Industry e. V."
(in short: BDEW) which has specified the following conditions for energy infeed:
● Riding through grid faults (FRT):
Not isolated from the grid for defined, short grid faults and disturbances.
These especially involve voltage dips or short-circuits between two or all 3 phases.
● Dynamic grid support:
During one of the previously mentioned voltage dips or short-circuits, a reactive current
must be impressed into the grid, which counteracts/corrects the voltage deviation.
● Provision of a steady-state reactive power for compensation if necessary
● Maintaining the limits of the voltage quality formulated in EN 50160
All energy suppliers must satisfy these conditions.
Grid infeed
System Manual, 04/2015, A5E03347436A
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