With power grids considered national security matters, the reliable operation of the system is of top priority to utilities.  This concern is amplified by the utility’s deregulation, which increases the system’s openness while simultaneously decreasing the applied degree of control.  Vulnerability Assessment (VA) deals with the power system’s ability to continue to provide service in case of an unforeseen catastrophic contingency.  Such contingencies may include unauthorized tripping, breaks in communication links, sabotage or intrusion by external agents, human errors, natural calamities and faults.  These contingencies could lead to a disruption of service to part or all of the system.  The service disruption is known as outage or blackout.  The paper outlines an approach by which feature extraction and boundary tracking can be implemented to achieve on line vulnerability assessment.