Cyber-Physical Modeling and Vulnerability Assessment of Substations for Transmission System Operator

In bulk power systems, the majority of the cyber and physical components interaction takes place in substations. However, in most of the cyber-physical power system models the physical layer is typically done using the bus-branch (BB) model, where each substation is considered as a single node. This approach will not capture the details of the cyber layer. This paper proposes a framework to model the substations using node-breaker (NB) models for physical system representation so that the detailed station configurations, the current and the voltage transformer positions, arrangements of protective relays, bay control units and associated communication infrastructure within the substations and its dependencies on the physical elements can be captured effectively using a single cyber-physical graph. Keeping a transmission system operator in view, who does not need power flow and security assessment tools for station operations and maintenance, a vulnerability assessment approach is proposed to assess the risk using some representative attack scenarios. The proposed approach is demonstrated using WECC 3 machine system for breaker and half station configurations.