Identification of Complex Faults in a Transmission Line

Virtual modes contain information on faults. There are local and pure-fault modes. The former is very simple yet can only be identified through two-end observation of the line regardless of the number and occurrence times of faults. The latter can be identified through one-end observation on the assumption that faults occur simultaneously. It is shown that local currents are capable of identifying three faults that occurred at different points in different phases of the line. These can be three single-phase faults or a combination of a single-phase fault with a two-phase fault in the other phases. The situation is more complicated in the case of two faults at different points of the same phase of the line. The local mode is not sufficient to identify them. The problem is solved by assuming that the fault currents are in phase with the respective voltages of the current mode. With one-end observation of the line, the fault components of currents can only help identify a fault of one of the two faulted phases that is nearest to the observation point.