A system including a vehicle having a motive electrical power path; a power distribution unit including a current protection circuit comprising a breaker/relay including: a fixed contact; a movable contact; a physical opening response portion responsive to a current value in the motive power circuit; a current source circuit electrically coupled to the breaker/relay and structured to inject a current across the fixed contact; and a voltage determination circuit electrically coupled to the breaker/relay and structured to determine at least one of an injected voltage amount and a contactor impedance value, wherein the voltage determination circuit comprises a high pass filter having a cutoff frequency selected in response to a frequency of the injected current.