Set-point Adjustment Attacks on Under Frequency Load Shedding Relays: A Risk Assessment Study

With emerging intelligent electronic devices (IEDs) and their integration into utility information and communication technologies (ICT) systems, the cyber-security of substation protection and control has become a crucial concern. An attacker can change the configuration of protection IEDs, once having successfully penetrated the cyber layers of the substation. Nevertheless, the power system has a defense plan in place to withstand any large deviations of the power system. Here, the attack vector consists of misleading the defense plan in such a way that it overreacts when a loss of generator is induced. This paper presents a Monte Carlo-based cyber-security risk assessment framework for coordinated cyber-attacks on under-frequency load-shedding (UFLS) and circuit breakers protection IEDs. In this attack vector, the attacker over-adjusts a limited number of UFLS relays and injects false tripping commands to the CB controller of step-up substations that result in wide-area load-shedding, uncontrollable frequency increase, cascading generator outages, and consequent blackouts. The attack likelihood is calculated based on the attacker’s resources and vulnerability indices. The IEEE 39-bus test system is utilized for conducting the simulations. The impact of the designed attack on the test system is calculated based on the frequency deviation and loss of load indices.