Vacha II Hydro-Electric Power Station Modernization with Compact 800

This document describes the modernization of the Vacha II hydro-electric power station in Bulgaria, where ABB replaced relay-logic control systems with its Compact 800 system, including AC 800M controllers, S800 I/O, and Compact HMI 800. The project also involved new excitation systems (Unitrol F), medium-voltage switchgear (UniGear ZS1), and auxiliary equipment, completed in a record eight months.