The document presents a reference architecture and accompanying profiles developed by the SEI ETF working group for industrial control systems in the electric energy sector. The reference architecture consists of six levels grouped into four zones, with physical processes on the lowest level and a hierarchy of controls in higher levels. Profiles were also developed for substations, generation, distributed energy resources, and control centers. The reference architecture and profiles are intended to serve as a common framework that can be customized for specific industrial control system implementations and domains.