The designs of the connecting transformer protection and two-out-of-three devices are studied for the triple protection scheme of an SVC-HVDC connected transformer and the requirement of enhancing group action time. In order to improve the reliability of the two-out-of-three device, the device adopts the dual CPU "and" export mode to eliminate a malfunction caused by the damage of a single device or a single circuit. Compared with conventional protection, triple protection system adds this two-out-of-three device, which causes the group action time of connecting transformer protection to be slow. In order to improve group action time, the technology of integrated optimization of differential protection, GOOSE multicast filtering of two-out-of-three devices, network storm function and GOOSE reception, parallel processing of logic operation, asynchronous start-up of start-up relay and outlet relay are adopted. Based on the above design, the performance of the transformer protection device meets the requirements of the GB/T-14285 standard and SVC-HVDC. This work is supported the Science and Technology Project of State Grid Corporation of China “Research on Advanced Function Support Technology for the Third Generation Intelligent Substation” (No. 52153218002L).