Fault location of two-terminal transmission lines with a small fault resistance

A numerical differentiation based algorithm for locating the faults occurring at the two-terminal transmission lines is presented in this paper. The fault line with two electric power systems at its two sides is modeled as two equivalent RL circuit transient processes. Im a transient process of RL circuit, the fault currents, which are much greater than the normal ones, include period component varying in pure sinusoidal waveform and non-period component with exponential decay. In any transient processes of RL circuits, its time constant includes such information as reactance and resistance of the lines can be computed by using the proposed algorithm. The time constant evaluated by the proposed algorithm is sent to another terminal of the line each other, and with the evaluated tin e constant and the known unit reactance and resistance of the lines, the fault distances apart from any buses can be estimated at a high accuracy of 99 996% , with a fault resistance varying from 1 ohm to 30 ohm. The simulation results carried out in Matlab with a study example show high accuracy and wide application.