Power System Reliability Evaluation with SCADA Cybersecurity Considerations

As information and communication networks are highly interconnected with the power grid, cyber security of the supervisory control and data acquisition (SCADA) system has become a critical issue in the electric power sector. By exploiting the vulnerabilities in cyber components and intruding into the local area networks of the control center, corporation, substations, or by injecting false information into communication links, the attackers are able to eavesdrop critical data, reconfigure devices, and send trip commands to the intelligent electronic devices that control the system breakers. Reliability of the power system can thus be impacted by various cyber attacks. In this paper, four attack scenarios for cyber components in networks of the SCADA system are considered, which may trip breakers of physical components. Two Bayesian attack graph models are built to illustrate the attack procedures and to evaluate the probabilities of successful cyber attacks. A mean time-to-compromise model is modified and adopted considering the known and zero-day vulnerabilities on the cyber components, and the frequencies of intrusions through various paths are estimated. With increased breaker trips resulting from the cyber attacks, the loss of load probabilities in the IEEE reliability test system 79 are estimated. The simulation results demonstrate that the power system becomes less reliable as the frequency of successful attacks on the cyber components increases and the skill levels of attackers increase.