Reliability Evaluation of Power Grids Considering Integrity Attacks Against Substation Protective IEDs

Secure operation of protective intelligent electronic devices (IEDs) has been recognized as a crucial issue for power grids. By gaining access to substation IEDs, intruders can severely disrupt the operation of protection systems. This paper develops an analytical reliability assessment framework for quantifying the impacts of the hypothesized integrity attacks against protection systems. Petri net models are used to simulate possible intrusion scenarios into substation networks. The cyber network model is constructed from firewall, intrusion prevention system (IPS), and password models, which are three types of defense mechanisms for protecting substation networks. In this paper, two main types of attacker actions on protective devices are recognized: 1) sending breaker opening commands through IED connections; and 2) changing IED settings. In this regard, a multistate Markov model is proposed for identifying possible consequences of cyber attacks on the protective devices. In addition, this model captures the essential remedial actions that are taken after a successful cyber attack against target equipment. Subsequently, an analytical approach based on the introduced Markov model is proposed for assessing power system reliability. The proposed framework is implemented on the modified IEEE reliability test system, and its effectiveness is demonstrated through extensive case studies.