This paper proposes a transformer air-cooling control system based on sectionalized single bus scheme, in consideration of the shortage of single bus scheme in typical transformer air-cooling system and the failure scenarios of air-cooling full stop caused by voltage loss of power supply when bus fault occurs. By analyzing the fault types and operation modes of this transformer air-cooling control system, the corresponding configuration schemes of automatic control and relay protection are proposed. When bus fault occurs in transformer air-cooling system, this scheme can locate and isolate the fault point accurately by relay protection and standby power supply automatic switching action, and avoid serious accidents caused by air-cooling system full stop. The test proves the validity of the solution to ensure the normal operation of the transformer air-cooling system. This work is supported by Science and Technology Project of the Headquarter of State Grid Corporation of China (No. 52020116000H) “Intelligent Cooling Control System for Micro-processor Transformer” and Science and Technology Project of State Grid Beijing Electric Power Company (No. 52023317000H).