Abstract
California’s decarbonization mandate and Renewable Portfolio Standards (RPS) are driving rapid growth in renewable energy customers connecting to the Southern California Edison (SCE) transmission system. Remote wind and solar generation connects to the greater Los Angeles basin through a limited number of long-distance transmission corridors, creating contingency profiles that legacy stand-alone Remedial Action Schemes (RAS) were never designed to manage. As SCE's portfolio of stand-alone RAS grew to over 20 schemes—each independently engineered, hardwired, and commissioned—interactions between schemes became increasingly complex, commissioning timelines lengthened, and the maintenance burden scaled faster than available resources.
In 2006, SCE initiated Proof of Concept for a Centralized Remedial Action Scheme (C-RAS): a single, software-defined system locating all protection logic in the Grid Control Center and Alternate Grid Control Center, with IEC 61850 GOOSE communication to monitoring and mitigation relays distributed across the transmission network. This paper presents a practitioner account of what was built, what two decades of production operation revealed, and where the platform is heading.
The C-RAS architecture centers on a redundant Central Controller System comprising three Unified Analytic Platform (UAP) nodes per subsystem, implementing a two-out-of-three voting scheme to ensure correct mitigation actions are always taken. Today, the SCE C-RAS monitors and controls 17 substations, managing 362 IEDs across fully redundant communication paths, achieving a 50ms end-to-end fault-to-mitigation response time verified through independent Real Time Digital Simulator (RTDS) testing. This paper also presents the 2023 Layer 3 R-GOOSE migration as a replicable model for utilities operating wide-area IEC 61850-based systems and discusses the emerging role of C-RAS as a foundational platform for next-generation grid control applications in the DER and AI era.