ifferential protection is often used as the main protection of large transformers in substations, but there are few cases where it is applied to 10 kV distribution transformers. A fire in a 2500 kVA large-capacity distribution transformer in a 10 kV distribution room is introduced, and the cause of the fault is analyzed. A possible short-circuit fault in the low voltage side is simulated by the software, and the action of the low and medium voltage protection under different conditions is discussed. Combined with the fault analysis results, the need for differential protection of a 10 kV distribution transformer in this case is studied. The results show that the differential protection can effectively solve the problem of the difficulty of the coordination between the setting value and the time delay range of the medium-low voltage protection, and at the same time, it can sensitively monitor the protection "blind zone" data under the grounding fault of the low-voltage side. The transformation scheme of the secondary system is designed, and the construction of an intelligent integrated monitoring system is completed with differential protection configuration as the core. The results show that differential protection can meet the extremely high supply reliability requirements of a 10 kV large-capacity distribution transformer. This work is supported by the National Natural Science Foundation of China (No. 51777082).