Abstract: An electronic filter for filtering the output signal of a current sensor of a circuit breaker is disclosed. The current sensor has an output signal characteristic similar to that of a Rogowski coil output signal characteristic that includes a third harmonic noise component in response to a switching primary current of the circuit breaker, and the circuit breaker has an electronic trip unit with an instantaneous pick-up setting responsive to the output signal of the current sensor. The electronic filter includes a first stage and a second stage. The first stage has a first transfer function that defines first characteristic poles and permits passage of the third harmonic noise component. The second stage has a second transfer function that defines second characteristic poles and filters the third harmonic noise component.

Abstract: An electronic filter for filtering the output signal of a current sensor of a circuit breaker is disclosed. The current sensor has an output signal characteristic similar to that of a Rogowski coil output signal characteristic that includes a third harmonic noise component in response to a switching primary current of the circuit breaker, and the circuit breaker has an electronic trip unit with an instantaneous pick-up setting responsive to the output signal of the current sensor. The electronic filter includes a first stage and a second stage. The first stage has a first transfer function that defines first characteristic poles and permits passage of the third harmonic noise component. The second stage has a second transfer function that defines second characteristic poles and filters the third harmonic noise component.