Abstract: As a critical component in power systems, current transformers serve as key devices for current transformation and high-low voltage isolation. The installation process directly determines the safe and stable operation of the power system. This paper takes the case of abnormal differential current in the protection device after replacing the 110 kV side current transformer of the No.1 main transformer in a 220 kV substation in Xinjiang as an example. Through on-site investigation, circuit analysis, and parameter comparison, this paper identifies the direct cause of the anomaly as non-standard installation techniques for the current transformer, while also exposing weak links in technical control and equipment acceptance by relevant departments. Addressing these issues, this paper delves into the technical shortcomings behind the incident from the perspective of the transformer's structural principles, and proposes preventive strategies in standardizing installation techniques, improving construction acceptance procedures, and enhancing personnel technical training. This research provides engineering references for the installation, commissioning, fault diagnosis, and operation and maintenance management of similar current transformers.