Page 259 - Fluid Power Engineering

226 Chapter Eleven

various parameters on the line like voltage, current, and fre-
quency in order to connect or disconnect the left-hand side
components from the transformer.
4. Three-phase transformer to raise voltage from low (LV) to
medium voltage (MV). Typically, this transformer will in-
crease the voltage from 480 or 690 V (depending on gener-
ator) to 11 or 69 kV (depending on design of MV line inside
the wind farm). The capacity of the transformer is specified in
terms of MVA, which is the product of the maximum voltage
and maximum current from the generator. In simple terms,
the MVA number is 15–25% higher than the rating of the gen-
erator. If the turbine is rated 2 MW, then a transformer rating
from 2.3 to 2.5 MVA may be chosen. These ratings also apply
to almost all components like the circuit breaker, fuses, and
metering equipment.

Another example of a single-line diagram that covers the entire
wind farm is in seen in Fig. 11-3. In this diagram, the following com-
ponents are illustrated:

IED MV to HV IED

Transformer
Radial feeders
Circuit Circuit
Breaker Breaker
Meter

Grid

WTGs

FIGURE 11-3 Single-line diagram of a wind farm in a radial topology. Individual
turbines are connected to a radial feeder.