Abstract: It is of significant value to develop digital twin transformers to support the intelligent operation and maintenance of power equipment. Currently, transformer possesses the general functions of computer-aided design and engineering simulation, however, the operation and maintenance oriented scenarios and performance digital twins are still in their infancy. Therefore, this paper proposes a new pattern which further expands computer-aided design, engineering simulation, and manufacturing into computer-aided maintenance+ (CAM+) for electric power equipment, including functions such as scenario updating, virtual-real fusion, fault location, and intelligent operation and maintenance. Firstly, this paper introduces the connotation of CAM+, and proposes the technical architecture of CAM+ pattern for digital twin transformers by combining the digital twin architecture of power equipment. Then, the key technologies involved in the CAM+ pattern, such as 3D scene visual modelling, high-precision sensing, coupled multi-physical field modeling and fast computation, dynamic deduction of virtual-real fusion, multi-source data fusion, intelligent assessment of state, and knowledge graph, are overviewed. Finally, the application of CAM+ for transformer scenario updating, parametric twinning and intelligent operation and maintenance is analyzed and the future challenges and directions of CAM+ are summarized.