Secondary protective control for mitigation of protection misoperations in electric power systems

This paper investigates the feasibility of a selective secondary protective control strategy proposed to maximize the likelihood of recovery from misoperations of the existing (primary) protection in a power system. A scalable stochastic discrete-state model is established, taking into consideration of the processes of protection misoperations and their mitigations. Such misoperations have been a main culprit of cascading failures in modern power systems. The likelihood of recovery from protection misoperations is quantified by a set of security indices that formally incorporate the uncertain knowledge of the continuous-state of rotor angles/speed deviations of synchronous generators and that of the discrete-state of equipment faults and primary protection misoperations. The proposed secondary protection leverages on the ever more available time-synchronized samples of networked sensors for diagnosis and fault-tolerant control to cost effectively improving power system reliability without altering the existing protection system. The technology readiness for implementing the secondary protective control is examined through a three-area test system.