Once More on Single-Terminal Algorithms for Location of Power Line Faults

The problem is actual for closed grids in the cases when the emergency data might be available only from the monitored end of the power line. The proposed algorithm is different for phase-to-phase short circuits and for phase-to-earth short circuits in power lines. In the former case, iterative calculations are made with complex quantities, using the known positive sequence impedance of a remote system; in the latter – with real numbers using the known zero sequence impedances of this system. In both cases, the ratio of phase conductor active resistance/line positive sequence reactance and the fact that the fault resistance is a real quantity are taken into account in the proposed algorithms. As a result of calculations, the positive sequence reactance from monitoring point to fault place and the fault resistance are obtained. Such an approach to the problem exerts influence on the shape of quadrilateral zone characteristics of distance protection. The right-side boundary of the protection operation zone can be set vertical (not tilted as it is now), the setting of this boundary can be common for all operation zones, each zone having only its own reactance setting, thus making unnecessary the load ingression feature in the distance protection. For radial lines, the same quantities are calculated using simpler mathematical expressions