Environmental Engineering Reference
For WFPSs Connected to the System at a voltage of 132 kV and
above the minimum connected impedance applicable to the whole
WFPS as a single unit will be specified in the Connection
Agreement or other agreement. The TSO's requirements for the
impedance will reflect the needs of the Transmission System
from the fault level and stability points of view. For WFPSs
Connected to the System at a voltage of 33 kV the short-circuit
ratio measured at the Connection Point shall not be less than 0.5.
Given wind speeds equal to, or faster than, the manufacturer's cut-
in point, and equal to, or slower than, the manufacturer's cut-out
point, for operation of the Wind Turbine Generators in the
WFPS , both as specified within the Connection Agreement for
the particular site, a WFPS must be capable of continuously sup-
plying Output in accordance with the power curve as specified/set
out in the Connection Agreement within the System Frequency
range 49.5-50.5 Hz. Within the Frequency range 49.5-50.5 Hz
there must be no reduction in Output whilst Frequency is falling.
Any decrease in Output to a level below the Output to be deliv-
ered in accordance with the power curve as specified/set out in
the Connection Agreement or other agreement occurring in the
Frequency range 49.5-47.5 Hz must not be more than pro rata
with any decrease below nominal Frequency .
The Output measured at each Wind Turbine Generator term-
inal should not be affected by voltage changes in the normal
operating range specified in CC .5.4.
In the event of a step change in voltage each WFPS shall
remain Connected to the Transmission System as specified
in the following diagram and the remainder of this CC .S2.3.6.
Fault Ride Through Capability of WFPSs
Voltage vs Times profile at WFPS Connection Point
CC.S2.3.5 Figure 1
Shows the time based requirement for a Wind Farm Power
Station to remain Connected to the Transmission System
during periods of reduced voltage on that System