Equivalent capacity of the Lower Voltage Ride Through for wind farm from overcurrent protection in power collection lines

Magnitude and duration of voltage sags are the most important two factors to the Lower Voltage Ride Through (LVRT) capacity of the wind generator. Since most voltage sags are caused by the system faults, and sag durations are controlled by the tripping time of overcurrent relay in power collection lines based on the sags´ magnitude. The specification of the LVRT capacity of wind generator is introduced into the operation characteristics of the relay in power collection lines. The evaluation model of equivalent LVRT capacity to overcurrent protection is proposed in paper, and the equivalent LVRT capacities from zone I and zone II relay are quantified. Improvement measures are also proposed.