Management of available transfer capability with growth in renewable resources

The California ISO´s functions include energy and related markets that provide non-discriminatory access to transmission facilities that have been placed under the CAISO´s operational control. The calculations of Available Transfer Capability (ATC), and management of market schedules to remain within ATC, are critical parts of the CAISO´s functions. This paper first describes these functions. An emerging challenge in management of California´s transmission grid is an increasing reliance on renewable generation, to achieve aggressive targets to reduce the current heavy reliance on natural gas as a fuel for electric generation and to reduce emissions of carbon dioxide, which will result in profound changes in markets and system operations. Among these challenges is that new renewable generation often involves remote resources, which affects the utilization of existing transmission, requires new transmission and increases some ancillary service requirements that must be deliverable through the transmission system. Achieving California´s renewable energy goals will include imports of intermittent resources, requiring coordination among system operators throughout the western states. Strategies for maintaining high utilization of California´ import capability are examined.