Improved method for locating faults upstream from distributed generation

This paper discusses the effect of distributed generation (DG) on fault location estimates when a fault occurs upstream from the DG. It is shown that the remote infeed from the DG affects the apparent impedance calculated from the substation and thus decreasing the fault location accuracy. This paper first evaluates the effects of the DG fault current contribution in the calculation of the apparent impedance. In addition to the evaluation, a method is proposed to improve the fault location estimates with the presence of the DG current infeed. Measurements taken at the DG terminal are used in addition to measurements taken at the utility substation to improve the fault location estimates. The method includes synchronizing both the substation and the DG terminal measurements, detecting the relative location of the fault with respect to the DG, and estimating load impedance and point of interconnection (POI) phasors. The approach is evaluated using simulated fault data acquired from time-domain modeling of a distribution system with the DG. The location estimates are shown to be accurate with an error of less than 2%.