Up to now, there is no precedent of applying two bipole lines (TBL) on the same tower technology of long-distance HVDC transmission project in the world. Owing to mutual influence between the two HVDC circuits on the same tower, the traditional protection of transmission line is faced with technical difficulties on fault pole identification, especially high grounded fault loop impedance. A new protection scheme of transmission lines for the double ±500kV HVDC circuits on the same tower is proposed. Based on electromagnetic decoupling method for TBL on same tower is proposed by analyzed the characteristic of coupling mutual induction, a four module components is proposed to decouple the network equation and analyze the fault modal network. On this basis, a novel method of fault pole identification based on the polarity comparison of line-mode back traveling wave is proposed. It has been made that validates the advantage of this novel protection strategy to identify the fault pole by simulation of PSCAD/EMTDC on the model of the TBL ±500kV HVDC system on the same tower in Xiluodu-Guangdong China.
