This paper introduces two typical cases of abnormal switch tripping during the first delivery of offshore wind power stations. Through the in-depth analysis

the reason for abnormal switch tripping in Guangxi offshore wind power station is due to the closing of no-load transformer generates excitation current

three-phase current value difference is large

resulting in zero sequence current exceeds the preset value of the protection; the reason for abnormal switch tripping in Zhejiang offshore wind farm is due to the long cable capacitance

closing the no-load transformer

causing series resonance

resulting in the current differential protection start. Taking proper measures to avoid the accident from happening again. This is a reference for commissioning of future offshore wind power projects.