FIELD: electrical engineering.
SUBSTANCE: short circuit conditions are detected at controlled feeder by determination of zero-phase sequence power direction at the first instant of breakdown. Zero-phase sequence current and voltage signals are used as initial data. Then, derivative of complex zero-phase sequence power is calculated. Note here that said calculation is made single time for industrial frequency component at the first instant of breakdown detected by excess of instant current or voltage magnitude over preset zero-phase sequence. Note here that direction of said derivative of complex zero-phase sequence power is used to define and store the short circuit direction at controlled feeder. Besides, additional control over current voltage over preset zero-phase sequence with persistence time equal to one or more industrial frequency cycles. This is done so that at termination of persistence time and stable direction of earth connection at controlled feeder, protection operation signal is generated.
EFFECT: selective protection, higher reliability and response.
6 cl, 8 dwg
