Electrical switching apparatus employing interlocks for first and second

Abstract

A circuit breaker includes separable contacts for movement between a closed position and an open position. An operating mechanism, which moves the separable contacts between the closed and open positions, has a closed state and an open or tripped state which corresponds to the open position. A current transformer senses electrical current flowing through the separable contacts as a sensed current. A trip mechanism employs the sensed current for tripping the operating mechanism to the tripped position to move the separable contacts to the open position. The trip mechanism includes a microprocessor which generates short delay and ground fault trip functions of electrical current and time. The microprocessor inputs a first interlock signal from a downstream electrical switching device which generates the first interlock signal with a first value when current through the downstream device exceeds a predetermined value and with a second value otherwise. The microprocessor generates and outputs a second interlock signal to an upstream electrical switching device in response to both of the first and second trip functions. The trip mechanism selectively trips the operating mechanism as a function of the first interlock signal, the first trip function, and the second trip function.