Abstract: A three-pole circuit breaker is for a three-phase load circuit including three phases and a line cycle. The three-pole circuit breaker includes three poles, each of which includes a set of separable contacts for a corresponding one of the phases of the three-phase load circuit, and a current sensor adapted to determine a plurality of current samples for the corresponding one of the phases during the line cycle. An operating mechanism is adapted to open and close the sets of separable contacts. A trip mechanism cooperates with the operating mechanism and is adapted to determine three current values from the current samples of the poles during at least about one half of the line cycle and to analyze differences among the current values, in order to detect a phase-to-phase arcing fault or a phase-to-ground arcing fault, and to responsively trip open the sets of separable contacts.