When a short-circuit fault occurs on a transmission line, it should be located rapidly and correctly in order to repair the faulted section, minimize the transmission line outage time, and restore power delivery as soon as possible. Therefore, development of a robust and accurate fault location technique under various fault conditions is a highly important research area.
In some low power densities areas, utilities are connected to an existing transmission line using a tapped line because of economic advantages. Such a configuration of transmission lines presents great difficulty in the task of fault location when the fault resistance is not negligible due to the infeed currents from different sources.
So far, different fault location algorithms for three-terminal transmission lines have been developed [1–18]. Several algorithms assume data to be available at local terminal known as one-ended fault location techniques [1-3]. Infeed currents and fault resistances are sources of errors in these fault location algorithms. Many other algorithms use data from more than one terminal. In  synchronized voltage and current waveforms measured at all three terminals are used to calculate the fault location. The authors utilized the prefault measurements at three terminals to synchronize the waveforms. An alternative approach is presented in  which similarly uses measurements from all three terminals of the transmission line but does not require synchronized data from all terminals. Using an iterative algorithm, the synchronization error is estimated and the fault location is obtained. This algorithm considers the lumped model of the transmission line in its calculations. This simplification results in increase of the estimation error in the case of long transmission lines and high impedance faults, for which the shunt capacitance is not negligible.
In  authors used synchronized three-phase voltages and currents at all terminals. They proposed an algorithm which applies voltage differentials at terminals to gradually reduce a multi-terminal line to a two-terminal line containing the faulted section. Then, a reactive power-based method was employed to locate the fault.
Ref.  uses current differentials at terminals to perform a similar reduction. The reduction procedure is very complicated and also normalizes section impedances when impedances are different. This is a source of error. Funabashi et al.  use synchronized current inputs from all terminals and use two different methods to locate the fault. The paper, however, fails to report results for three-phase and two-phase to ground faults.
Exchanging the minimal amount of information between the line terminals is considered in [10-13]. The use of negative-sequence quantities for fault location in three-terminal lines is proposed in , which uses magnitude of negative-sequence current as well as the negative-sequence source impedance of remote terminals. The technique introduced in...