Excessive Over-Voltage in Long Cables of Large Offshore Windfarms

Large offshore windfarms are connected to onshore transmission grids through long high-voltage cables. When a large offshore windfarm goes into isolated operation with its high-voltage cable, for example by an action of the on-shore main-circuit breaker, there is a risk of significant over-voltage in the cable and the windfarm transformer. This paper analyses such a situation for both an existing and a planned large offshore windfarm in Denmark.