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A novel line non-unit protection principle based on HHT energy spectrum is proposed in the paper. Influence of line trap and the bus-to-ground capacitance of the transmission line to high frequency component of fault traveling wave is analysised, energy of high frequency component of the traveling wave detected in internal area is more than that of external area due to the hindrance of line trap and bus-to-ground capacitance. The differences between internal and external faults are used in realizing the protection. HHT is used to get energy spectrum, and the energy spectrum is used to distinguish the internal and external faults. ATP/EMTP simulation results show that the protection can act immediately, it can realize full line protection and can distinguish types of fault. It is an effective non-unit EHV transmission line Protection method.