DIGITAL FILTERING METHODS IN MICROPROCESSOR BASED PROTECTIVE RELAYING

ABSTRACT Most protective relaying schemes use single frequency information from transient current/voltage signals to discriminate faults. In microprocessor based protective relaying, digital filtering is an attractive method of extracting effective frequency components. This paper presents three digital filtering methods based on frequency-spectral analysis for microprocessor based protective relaying: unit-combined filters, assigned zero-points filters and narrow band-pass filters. Test results are also presented.