Method for avoiding voltage instability in an electrical grid of an offshore wind park, the offshore wind park electrical grid being connected at a first end of a high voltage alternating current (HVAC) transmission and the main land electrical grid being connected at a second end of the HVAC transmission, each of the wind turbines being connected to the wind park electrical grid, the method comprises determining a main land phase angle at or near the second end of the HVAC transmission; measuring an individual wind turbine phase angle at one or more wind turbines; determining the difference between each of the measured individual wind turbine phase angles and the main land phase angle; and determining whether the difference between one of the measured individual wind turbine phase angle and the main land phase angle exceeds a threshold phase angle difference.