An online operational risk management method is presented in this paper. In this method, a risk-based direct-current (DC) optimal power flow approach is utilized to replace a traditional security-constrained DC optimal power flow approach. This risk management method is integrated into a commercial energy management system/dispatcher training simulator system to monitor and control system operation risk online. Comparison of the approach with traditional security assessment shows significant benefits over the long term via cost reduction and risk mitigation. A case study provides supporting evidence of risk mitigation in terms of steady-state angular separation reduction and cascading prevention.