Relay protection method for phase to phase fault of circuit

The invention discloses a relay protection method for phase to phase fault of a circuit, which belongs to the technical field of relay protection of electrical power systems. Whether the protection is actuated or not is determined through calculating the angle of the vector difference between advanced fault phase to phase actuating voltage vector and voltage vector at the fault of vector difference between fault phase to phase voltage vector and voltage vector at the fault. The method eliminates influence of distributed capacitance of a high voltage/extra-high voltage/ultra high voltage powertransmission line and has good capacity of resisting transition resistance and load current.