Nomorecatering, to answer your question re-individual wind turbines. They are individual alternators turning out AC. This output is rectified to DC and transmitted to the farm substation. In the substation, the load is sensed, from here the power is converted from DC to synchronous AC at the one point for transmission into the grid. It is at this point where the "Software Issue" occurred.
Two lines were subsequently found to be ok and were returned to service without need of repair.