DEVICE FOR FILTRATION AND EXTRACTION OF THE FIRST HARMONIC IN MICROPROCESSOR DEVICES OF RELAY PROTECTION OF FEEDERS OF CONTACT NETWORK ON THE BASIS OF PLL Russian patent published in 2019 - IPC G01R31/00 

FIELD: measuring equipment.

SUBSTANCE: invention relates to instrumentation and is intended for continuous extraction of the first harmonic of voltage and current from outputs of measuring transformers in microprocessor contact network feeder protection devices. Summary: device comprises elements of connection to measuring terminals of low-voltage current and voltage transformers, low-frequency filters by measuring channels of current and voltage, phase automatic frequency control units for obtaining control reference signals, rectifier modules and resonant inverters for extraction of the first harmonics of current and voltage. Device implements preliminary filtration of nonsinusoidal signals taken from outputs of low-voltage current and voltage measuring transformers with subsequent phase tracking of time of action of their zero values by means of phase-locked loop circuits and further inverting of simultaneously rectified signals from outputs of measuring transformers in order to isolate first harmonics of analyzed current and voltage.

EFFECT: simplification of relay protection microprocessor devices and increase of their operation selectivity.

1 cl, 2 dwg