Trip unit providing short circuit zone location detection, electrical switching apparatus and system including the same

摘要

A trip unit includes a current sensor to sense a value of current flowing through a conductor, a circuit to receive first frequency pulses having a number of first frequencies from the conductor, a transmitter to transmit second frequency pulses having a second frequency different than the first frequencies to the conductor, and a processor having a routine. The routine inputs the sensed value of current from the current sensor, determines if the sensed value of current exceeds a predetermined value and responsively causes the transmitter to transmit the second frequency pulses having the second frequency to the conductor, monitors within a predetermined time after determining that the sensed value of current exceeds the predetermined value if a number of the first frequency pulses having the number of first frequencies is received by the circuit, and responsively delays outputting a trip signal, and, otherwise, immediately outputs the trip signal.