A feeder protection method against the phase-phase fault using symmetrical components

The method of symmetrical components simplifies analysis of an electric circuit during the fault and represents an important tool for the protection engineers. In this paper, the symmetrical components of the fault current are used in a new feeder protection method for the maritime applications. The new method is effective against the phase-phase fault and relies on evaluation of the ratio of negative-sequence to positive-sequence current to detect such faults. It is shown that the proposed ratio is a complex number and its magnitude is associated with the presence of the phase-phase fault in a radial feeder, while its argument is an indicator of the fault direction. Precisely these information are used in this paper to detect the phase-phase fault and to indicate the faulted section of the feeder. Using PSCAD, the new method is implemented in a test Medium Voltage feeder with variable generation and relatively reduced short-circuit currents, thus resembling the electric network on a ship. The simulation results demonstrate that the proposed method of protection provides an improved performance compared to the conventional OverCurrent relays in a radial feeder with variable short-circuit power.