An apparatus and method for detecting the loss of a current transformer connection coupling a current differential relay to an element of a power system

摘要

Disclosed is an apparatus and method for detecting a loss of a current transformer connection coupling a protective relay to a power system element of a three-phase power system and providing a plurality of secondary current waveforms of the three-phase power system to the protective relay. The apparatus includes a first logic circuit and a second logic circuit configured to provide corresponding first and second binary signals in response to respective comparisons of calculated current value(s) of a plurality of like-phase digitized current sample streams to respective threshold values. The apparatus also includes a set reset flip-flop having a set input adapted to receive the first and second binary signals to provide a third binary signal. The third binary signal indicates loss of a current transformer connection when the set input is asserted and indicates no loss of a current transformer connection when the reset input is asserted.