Source-independent protection scheme for transmission lines in IBR dominated systems

In recent decades, the integration of Inverter-Based Resources (IBRs) into power systems has increased significantly to facilitate energy decarbonization. Unlike conventional Synchronous Generators (SGs), which have predictable fault responses and fault current contributions, IBRs produce limited fault currents, with behaviour highly dependent on the design of their embedded controllers. This difference can compromise the performance of conventional protection schemes, which often rely on the fault behaviour of SGs. To address this challenge, this paper proposes a novel source-independent protection method for transmission lines energised from networks with high proportion of IBRs. The approach is based on the inherent characteristics of the protected line, modelled as a two-port network with ABCD parameters. By mathematical modelling of ABCD parameters, the local values of voltage and current are estimated using remote measurement data, and then compared with the corresponding actual measured values of quantities. During normal operation or in the event of external faults, the estimated and measured values exhibit close agreement. In contrast, internal faults cause a marked deviation between the two, signalling a fault in the protected line. MATLAB/SIMULINK studies under various fault types, resistances, and locations demonstrate that the method outperforms conventional differential protection, and remains unaffected by the line charging current. It also achieves very high sensitivity to high impedance faults, making it suitable for future IBR-rich power systems.