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6.3 Fault Ride Through (FRT)
According to BDEW:
2.5.1.2 Dynamic network support
Dynamic network support means voltage control in the event of voltage drops
within the high and extra-high voltage network with a view to avoiding
unintentional disconnections of large feed-in power, and thus network collapse.
In the light of the strong increase in the number of generating plants to be
connected to the medium-voltage network, the integration of these plants into the
dynamic network support scheme is becoming ever more important.
Consequently, these generating plants must generally participate in dynamic
network support even if this is not required by the network operator at the time of
the plant’s connection to the network. That means that generating plants must be
able in technical terms
not to disconnect from the network in the event of network faults,
to support the network voltage during a network fault by feeding a reactive
current into the network,
not to extract from the medium-voltage network after fault clearance more
inductive reactive power than prior to the occurrence of the fault.
These requirements apply to all types of short circuits (i.e. to single-phase,
two-phase and three-phase short circuits).
Just like in the Transmission Code 2007 7, a distinction is made in these
guidelines between type-1 and type-2 generating plants with regard to their
behaviour in the event of network disturbances. A type-1 generating unit exists
if a synchronous generator is directly (only through the generator transformer)
connected to the network. All other plants are type-2 generating units.
The following conditions shall apply to type-2 generating plants, taking the
Transmission Code 2007, Section 3.3.13.5, into account:
Generating units must not disconnect from the network in the event of
voltage drops to 0 % Uc of a duration of ≤ 150 ms.
Below the blue line shown in Figure 2.5.1.2-2, there are no requirements
saying that generating plants have to remain connected to the network.
Voltage drops with values above the borderline 1 must not lead to instability or to
the disconnection of the generating plant from the network (TC2007; 3.3.13.5,
section 13; extended to asymmetrical voltage drops).
If the voltage drops at values above the borderline 2 and below the borderline 1,
generating units shall pass through the fault without disconnecting from the
network. Feed-in of a short-circuit current during that time is to be agreed with
the network operator. In consultation with the network operator, it is permissible
