A circuit breaker having a series arc fault detector and method of operation is provided. The series arc fault detector measures the RMS current and monitors current stability in response to a change in current levels. The sensitivity of the series arc fault detection is changed in response to the current satisfying a stability criterion. The circuit breaker further enables and disables series arc fault detection based on an enable threshold. The enable threshold is set based on the level of sensitivity being used to detect a series arc fault.