Resilient Protection System Through Centralized Substation Protection

Power systems are experiencing drastic changes with the introduction of renewables and customer owned resources. These changes introduce new challenges in protection, control, and operation of power systems. In protection, it is necessary to develop new methods that are immune to the new characteristics and they avoid relay misoperations. In particular, any protection system is vulnerable to hidden failures. This paper introduces a new dynamic state estimation-based centralized protection scheme (DSEBCPS) at a substation level. The system supplements dynamic state estimation-based protection for individual zones known as “setting-less relays” to secure their operation against hidden failures. The DSEBCPS communicates with the setting-less relays via the station bus and obtains essential information from each protection zone, such as phasor quantities and breakers/disconnects status. This information is processed by the DSEBCPS to estimate substation topology and states. Specifically, the DSEBCPS performs dynamic state estimation in the quasi dynamic domain once per cycle to detect any abnormality within the substation. Upon detecting abnormalities, the DSEBCPS performs hypothesis testing to identify the source of the abnormality, that is, a fault or a hidden failure. Upon detecting a hidden failure, the DSEBCPS identifies the compromised data, replaces this data with estimated values by using the substation estimated states and model. The corrected data are used by the setting-less relays, enabling self-healing characteristics. The proposed capability to detect hidden failures and correct the effects of these failures in real time makes the setting-less relays secure against misoperations and bridges a critical gap in protection systems. This capability is demonstrated through numerical experiments that include several scenarios of hidden failures. The integration of the proposed scheme with the individual protection zone relays form a resilient protection and control system, which is self-immunized against hidden failures.