Improved mathematical models of transmission lines are used to develop a fault location method which copes with high-frequency transients. The telegraph equations used for a line model are solved by the method of characteristics using voltage and current samples as boundary conditions taken at one end of the line within the first few milliseconds of fault inception. Estimates of voltage and current profiles for the entire length of the transmission line during the fault are obtained. Criteria for fault location are based on a formulation involving these voltage and current estimates. For fault location on multiphase systems the concept of modal analysis is used in enhancing the fault-locating capability of this algorithm.