FAULT DETECTION IN A POWER TRANSMISSION SYSTEM

Fault detection during a power swing in a power transmission system is described. Voltage and current measurements are obtained for each phase at a terminal of the power transmission system. Based on measurements obtained, a value of change in an impedance angle for each phase-to-ground loop and each phase-to-phase loop for each sample of the voltage and current values is calculated, where the value of change in the impedance angle is a difference between impedance angles of two samples separated by a predetermined interval. The average values for change in impedance angle based on a predetermined number of values of change in the impedance angle for each phase-to-ground loop and each phase-to-phase loop is calculated. The average values are compared with a threshold range of change in impedance angle. Based on the comparison, a fault in one or more of the phase-to-ground loops or phase-to-phase loops is detected and classified.