ACCURATE FAULT IMPEDANCE LOCATING ALGORITHM

Fault resistances affect the accuracy of short-circuit location, when distance to the fault is determined by means of measuring reactance at one end of the transmission line. This is because the current which flows through the fault resistance is slightly shifted in phase with respect to the current measured at the end of the line in question, due to the effect of the prefault load current. As a result, the fault resistance is recognized as an apparent impedance with both resistive and reactive components. The latter produces an error in the fault location, as it affects the measured reactance. A simple algorithm is presented which compensates for the error, and makes it possible to locate short circuits accurately, even if fault resistances are comparatively high.