Implementation and Support of State Estimator in California ISO Electric Grid Operation

This chapter provides an overview of California Independent System Operator (CAISO) in the United States and CAISO’s role in operating the electric grid both in California and western parts of the United States. Considering the usage of State Estimator (SE) in the industry for many years, only a high-level overview of the SE with certain unique features of SE implementation at CAISO is provided. An overview of the Energy Management System (EMS), in which SE is integrated, and the architectural framework for data transfers in and out of SE to support real-time operations, including market and reliability applications, is also provided. The focus of this chapter is on SE solution quality and tuning approach to achieve targeted levels of solution quality. To support this, a balancing authority (BA) area/zone-level SE solution quality metrics are defined, which make up the foundation in supporting SE solution quality. Considering the size of the model at CAISO, SE solution quality support is organized by balancing area (BA)/subarea (zone) with definable targets. Unique aspects of supporting SE solution quality at CAISO are explained, with emphasis on reference models for comparison, metrics used in different phases of network model promotion leading to operational model and respective metrics used, and tuning practices which involve reactive and proactive tuning supplementing each other. Considering the critical role of SE in CAISO real-time operations, details of how the SE is supported at various levels are provided such as operational support on a 24 × 7 basis, tuning SE for its output to match closer-to-expected operational values, upkeep of real-time telemetry feeding to SE, identification of mismatches in the model, and identification of enhancements to support solution quality.