Aviation needs to meet the ambitious targets of the European Green Deal. This means a step change is needed towards hybrid electric regional aircraft to significantly reduce the fuel burn. This can only be accomplished with power distribution networks that can safely handle the high power and high voltage levels, ultimately up to several Megawatt. The HECATE project will address the associated challenges of system weight and power density, high voltage challenges with lightning, arcing and electromagnetic interference as well as optimized thermal management, in addition to digitizing the design process with digital twins. This will lead to transformative technology bricks, which are holistically optimized at system integration architecture level. The HECATE project will demonstrate a >500 kW architecture in a copper bird at TRL5. This will provide a clearer understanding of high voltage challenges and how to mitigate them, with a scalability roadmap towards CAJU Phase 2 flight demonstration and exploitation in a 2035 new built Hybrid Electric Regional aircraft. Also, environmental impact and LCA will be assessed. For optimal alignment and ensuring certifiability, HECATE will establish relationships with other Clean Aviation projects (e.g. HER-01 for MW propulsion, HER-02 for thermal, TRA-01 for architecture, TRA-02 for certification) and authorities and standards groups (e.g. EASA, EUROCAE).