Distance relays’ phase and ground elements at either circuits of the parallel transmission lines undergo miscalculation of the correct fault impedance when facing inter-circuit faults. This paper proposes a distance protection approach for untransposed parallel lines in case of phase-phase-ground inter-circuit faults, which can also be served as the fault locator as its auxiliary function. It is a demanding task compared to that of transposed lines due to the mutual coupling between all six phases of the line circuits. Considering the intended faults with the fault arc and ground resistances, the line circuit model is analyzed on a time-domain basis, resulting an equation that is mathematically a linear combination of designated functions. This would provide a great chance of establishing an adaptive linear combiner with windowed inputs (W-Adaline) in consistence with the equation derived. The W-Adaline with its simple structure is capable of giving a fast and accurate estimation of the fault distance in an online manner, which is exploited for both the line distance protection and fault location. The proposed approach is readily implementable and is independent of the system configuration. It operates robustly in high-ground resistance, variable fault arc resistance and noisy conditions. Through extensive simulation studies in PSCAD/EMTDC, performance of the proposed approach would be investigated and verified in a variety of fault and system loading conditions.