Transmission line adaptive protection scheme: A new fault detection approach based on pilot superimposed impedance

•Novel adaptive protection scheme for transmission line based on PSI.•Adaptive update of protection threshold when the network structure is changed.•Facilitating the single-pole-tripping through rapid detection of the faulted phase.•Robust protection in the case of HIF and series compensation lines.•Identifying the internal faults from external ones in less than one cycle.