The Value of Recovery Transformers in Protecting an Electric Transmission Grid Against Attack

This paper incorporates, as part of an attacker-defender (AD) model for an electric power transmission grid, an inventory of recovery spares for high-voltage transformers (HVTs). In this sequential-game model, an attacker first uses limited resources to disable grid components, seeking to maximize second-stage total cost. This value corresponds to a defender who operates the damaged grid to minimize generating and economic load-shedding costs. The defender's problem includes 1) optimal power-flow solutions to represent post-attack operations, 2) optimized replacement of disabled HVTs with quickly installable recovery spares, and 3) longer-term replacements using new procurements. Global Benders decomposition, with a mixed-integer subproblem, solves the AD model; new enumerative techniques help solve the decomposition's master problem and subproblems. Computational tests demonstrate tradeoffs between the number of recovery spares and worst-case total cost, and show how the model could help guide an inventory strategy for recovery spares in an adversarial setting.