Abstract: To investigate the causes of low voltage protection, overvoltage protection, and stator single-phase grounding protection actions during the performance test of a certain type of gas turbine, a comprehensive analysis of the fault process and equipment operating status was carried out through on-site inspection, fault point location, theoretical analysis, and verification tests. The cause of the fault was identified as residual metal foreign matter at the nozzle of the metal heating tube in the 2000kW range of a certain load box, which triggered an instant breakdown, leading to a single-phase grounding fault during dynamic load increase and decrease, thereby activating the generator protection devices for low voltage protection, overvoltage protection, and stator single-phase grounding protection. This paper provides theoretical analysis, fault location, and effective treatment for the stator single-phase grounding fault during the performance test of the gas turbine. The entire research process can serve as a reference for the troubleshooting and handling of grounding faults in performance tests of similar gas turbines and provide a theoretical basis for the analysis of stator single-phase grounding protection in generators.