Protective relay system for performing selective-pole trip determination

摘要

Apparatus for performing selective-pole trip determination is included in each protective relay of a current only monitoring protective relay system for protecting an electrical transmission segment of a power system network against faults. Current signals from the phases of the transmission segment are provided to a sequence network of the apparatus for conversion into positive and negative sequence component signals for each phase. A zero sequence component signal is also derived. A logic circuit is provided for each of the phases of the transmission segment and is governed by the corresponding sequence component signals and phase shifted variations thereof to detect a single-pole fault exclusively in the corresponding phase and generate a signal in response to the detection. An internal trip detection enables each phase logic circuit to generate its corresponding trip signal. Each protective relay further includes multi-phase trip logic circuitry governed by the positive, negative and zero sequence component signals and phase shifted variations thereof to generate phase-to-phase and phase-to-phase-to-ground fault signals.