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A method for fault type discrimination and faulted phase identification using instantaneous local current measurements is proposed. Seven current components are obtained from the measured three-phase instantaneous currents through a transformation and band passed filtered to remove the fundamental components and high frequency content. Upon detecting a fault, nine fault discrimination indices are computed taking different ratios of the maximum rates of change of these filtered current components. The indices are used to (i) separate ground faults from the phase-to-phase and three-phase faults, (ii) discriminate phase-to-ground from phase-to-phase-to-ground faults, (iii) differentiate phase-to-phase faults from the three-phase faults, and (iv) identify the faulted phases. As the indices are ratios, decisions are less affected by the fault resistance. The algorithm was validated using a power system simulated in PSCAD/EMTDC. Extensive testing involving more than 10,000 fault scenarios showed that fault type and faulted phases can be successfully identified. The algorithm found some difficulty in identifying the phases involved in phase-to-phase-to-ground faults at certain fault inception angles, and one of the thresholds can be affected by the transposition scheme. [ABSTRACT FROM AUTHOR]

A simple and yet dependable technique for fault-type identification in HVDC transmission systems is presented in this paper. A set of indices is defined for pairs of rate of change of current measurements to identify the pole(s) involved in the fault to discriminate the ground faults from those involved with the dedicated metallic return conductor. The proposed fault discrimination method will identify the faulty pole within a 1-ms window, and therefore, it can be used to improve the sensitivity and reliability of DC fault protection. Furthermore, the knowledge—whether or not the dedicated return conductor is involved in the fault—is useful for determining the post-fault configuration of bipole grids. Considerable discrimination margins are observed during the rigorous evaluation of the technique for two-conductor and three-conductor HVDC systems under various fault scenarios, for both considerably long overhead transmission lines and cables. The indices can be computed using local current measurements made using low-bandwidth sensors. They are independent of the fault resistance, and therefore, settings can be found easily. [ABSTRACT FROM AUTHOR]