Distance Protection of Double-Circuit Lines with Inverter-Based Resources and Real-Time Validation

Inverter-based resources exhibit control dependent, modulated fault voltage and current waveforms, posing significant protection challenges, particularly for high resistance faults on double-circuit transmission lines. To overcome these, a source independent method for fault impedance calculation immune to fault resistance effect is proposed for distance protection of double-circuit transmission line. This method is based on sequence components of common and differential terms of the voltage and current phasors measured at the local end which avoids line mutual coupling effect. In the method, the phase angle of fault path current is determined from the differential sequence component of current without estimation of source impedances or assumption of homogeneity. The maximum fault-current phase angle error remains around 0.2◦, while the apparent impedance estimation error remains around 3% for a transposed line configuration. The performance of the proposed method is assessed on the IEEE 39-bus system integrated with inverter-based resources under varying fault parameters, grid-code-compliant converter control strategies, and short-circuit ratios, demonstrating accurate and robust operation across diverse system conditions. Real time hardware-in-the-loop studies further demonstrate its reliable performance and practical applicability under realistic operating conditions.