Abstract: This article analyzes and inspects the tripping of the 35 kV collector line of a certain offshore wind farm, and determines that the cause of the circuit breaker tripping of the collector line is the breakdown of the submarine cable terminal of the 3# wind turbine connected to the collector line, causing a single-phase grounding fault. After replacing the submarine cable terminal of the 3# wind turbine, the circuit breaker of the 3# wind turbine tripped during power transmission. Upon inspection, it was found that the CT secondary wiring terminal of the 3# wind turbine circuit breaker was loose, causing the self-produced zero sequence current to overcurrent, resulting in misoperation of the zero sequence protection and causing the circuit breaker to trip.