The U.S. Interconnection Queue System: Cascading Vulnerability Analysis and a Resilience Engineering Framework

Abstract: As of 2025, the U.S. interconnection queues, the grid-access gateway for new generation and storage, contain roughly 8,200 projects totaling 2,061 GW of capacity. Only 13% of capacity queued in 2000-2020 (19% by project count) has reached operation. We argue that the queue architecture is vulnerable to self-reinforcing project withdrawal cascades arising from restudy and cost reallocation, independent of study delays. Adapting failure contagion models from financial and interdependent infrastructure networks, we model the queue as a complex adaptive system and test it with a statistical analysis of withdrawal temporal clustering and co-withdrawal across seven ISO/RTOs and a stylized network contagion simulation of cost-sharing interdependencies with circuit-breaker interventions. Using LBNL project-level data through 2025, we find temporal clustering (dispersion indices 5.0-102.4; p < 0.001) and identify 39 monthly withdrawal bursts with the largest cluster-dated, reaching 67.4x the regional mean. Withdrawal timing is concentrated within technology categories in all seven regions (1,000-permutation test; z = 2.58-4.78, p <= 0.005). Co-withdrawal within cohorts is significant only in four regions (0.5-1.8 percentage points). The model yields net cascade amplification of 1.0-1.5x at low-to-moderate connectivity (average network degree k = 3-10). At k = 20 a phase-transition-like shift to systemic instability occurs, exceeding 8.7x amplification at a 10% shock (97.7% cascade size); a boundary condition of the stylized network that disappears under pro-rata redistribution. Capping per-neighbor cost reallocation reduces cascade magnitude by up to 20% relative to no intervention, with a 44% lower mean per-neighbor transfer. These findings characterize the interconnection queue as critical infrastructure with cascading vulnerability whose severity is conditional on cost allocation design.