Abstract: As a flow control device, a phase shifting transformer can dynamically adjust the transmission power of power lines, greatly improving the flexibility of power flow transmission. However, due to its special wiring form and internal structure, a single-core phase shifting transformer with an asymmetric hexagonal connection form has more complex fault characteristics than a conventional power transformer, which poses difficulties to the configuration of its intrinsic protection. To solve this problem, this paper first clarifies the topological structure and working principle of the single-core phase shifting transformer with an asymmetric hexagonal connection. Based on further analysis of its magnetic circuit structure, a complete differential protection scheme is established for this special structure of the phase-shifting transformer, using basic circuit principles such as Kirchhoff's current law and electromagnetic induction law. This scheme reflects inter-turn faults, turn-to-ground faults, and short-circuit faults of the lead wires between the regulating and excitation winding through two sets of level balance and one set of magnetic balance differential protection. It achieves comprehensive coverage of internal faults in the phase-shifting transformer and enables fast determination of fault location and fault type. Finally, a simulation model of the new single-core phase-shifting transformer is built on the MATLAB/Simulink simulation platform, and extensive simulations have verified the feasibility and effectiveness of the proposed scheme.