PC-BASED PROTECTIVE RELAYING ALGORITHMS FOR BUS BARS USING DIGITAL-FILTERS

The paper reports the development of protective relaying algorithms fo r bus bars using digital filters. An efficient algorithm based on the recursive constraint transfer function model of the IIR band-pass filt er has been used to extract the 50 Hz frequency component for realizin g the various protective functions for a bus bar. A fourth-order adapt ive filter is used for tracking the centre frequency components of vol tages and currents. The proposed relaying algorithms provide variable- bias differential protection logic coupled with undervoltage check/neu tral current check features to ensure a high degree of reliability and freedom from unwanted tripping of circuit breakers. The developed alg orithms have been tested with simulated input signals representing var ious normal and abnormal bus bar conditions and the scheme as a whole responded efficiently.