As the complexity of power systems continues to increase and the penetration rate of distributed generation (DG) rises, traditional distance protection schemes face a dual, severe challenge. Specifically, the non-negligible fault transition resistance in grounding faults often leads to underreach, compromising protection speed, while the fault current contribution from integrated DG units severely distorts the measured impedance, increasing the risk of maloperation or failure to trip. To overcome these critical limitations, this study proposes an improved distance protection scheme that simultaneously accounts for and effectively compensates for both fault transition resistance and the impact of DG integration. By leveraging the known R/X ratios of transmission lines and employing voltage–current phasor analysis, the proposed method enables the accurate and rapid estimation/correction of the line impedance between the relay and the fault point. This work provides a robust and low-cost solution for protective decision-making in contemporary power systems.
Chen et al. (Mon,) studied this question.