Analysis on Serious Wind Turbine Generators Tripping Accident in Northwest China Power Grid in 2011 and Its Lessons

On February 24,2011,equipment fault occurred at 35kV side of Qiaoxi substation connected with the first wind farm of Gansu province,and this fault caused a serious wind turbine generators tripping accident,so that 598 wind power generators were tripped off and the lost output of the wind farm was 837.34MW during the fault period because the wind turbine generators did not possess low voltage ride-through ability and the reactive power compensator of the wind farm did not possess the ability of automatic regulation.Operational condition of Northwest China power grid before the accident is presented in detail and detailed description of occurrence,expansion and restoration of the fault are given,and the reappearance of the fault is carried out by simulation.Experiences and lesson of the fault are summarized.To prevent the recurrence of such a serious wind turbine generators tripping accident and to ensure the secure and stable operation of power grid,following suggestions are proposed: strengthening the maintenance of protective relayings;enhancing low voltage ride-through ability of wind turbine generators;improving the renovation and management of reactive power compensation devices of wind farms;standardizing the operation of wind power generation units under the 1.1 time of rated voltage;directly switching out the 35kV feeder,in which single-phase short-circuit fault occurs.