Electrical losses in Openwind are calculated using nominal phase voltages and wind turbine generator rated power (MW) within a 3-phase electrical system using the following electrical relationships and formulas:
Where:
I = Phase current (A)
PGEN = Wind Turbine Generator rated power (W)
VPHASE = Nominal phase voltage (V)
R = Total resistance of one phase conductor of a circuit (Ω)
RLEN = The resistance per unit length of a single-phase conductor (Ω/km), provide by the cable manufacturer.
L = Length of a three-phase circuit (km)
PLOSS = The calculated power loss (W)
In addition to line losses for the medium and high-voltage cables, Openwind calculates the losses due to the substation transformer and the turbine transformers.
The electrical losses are calculated using the energy capture cases. For time series cases the collector system is simulated for each time-step and the appropriate electrical loss calculated. In the case of a probabilistic energy capture, each case (wind speed and direction) is simulated as a separate case taking account of the relative speed-ups across the site.
Transformer losses are calculated as a linear function such that:
Ploss = NoLoadLoss + FullLoadLoss*(P/Prated)2
Where Prated is the rated power of the transformer, Ploss is the power lost by the transformer, P is the power going through the transformer, NoLoadLoss and FullLoadLoss are the losses at no and full load respectively.
Electrical losses are calculated after all other losses have been applied.