All of the recently proposed fault location approaches for power distribution systems require prior knowledge of system variables at the faulted section. This is a problem in power distribution systems because these usually have measurements of voltages and currents only at the main substation. As a consequence, this document proposes a power system modeling and a forward sweep-based method aimed to estimate the values of voltage and current at the faulted section, using the power system parameters, topology and the measurements at the substation. By applying the new approach here proposed, the distance estimation error is reduced in nearly 1% from the original value. It helps to develop more precise methods for locating faults in power distribution systems, contributing in this way to improve the supply continuity and as a consequence the power quality.