Precise distance to fault locator with two end phasor measurement transmitted via serial protection data interface

Fault locator functionality is a standard feature in modern numerical feeder protection devices for transmission systems. It is common practice to calculate the fault location via an impedance measurement separately at each line end. All calculation techniques used to date in this ldquosingle endedrdquo fault location exhibit limited accuracy. The accuracy that can be obtained is limited by natural constraints. The common factors that influence the accuracy are described below. Hereafter, the fundamental improvement provided by the ldquotwo endedrdquo fault locator, which in addition uses the measured values from the opposite line end, are described.