This paper presents commissioning details of a coordinated reactive power-voltage controller (CQVC) installed in a multimachine steam power plant (SPP). The CQVC regulates reactive power and voltage of a 1992MVA multimachine SPP. After briefly introducing basic control principles and relevant details about the CQVC's implementation, CQVC parameterization and tuning are thoroughly discussed. Once commissioned,the CQVC performance under various operating conditions is assessed. It is shown that the CQVC successfully maintains an HV busbar voltage and allocates reactive power to participating generators in accordance to their capability. Numerous CQVC responses recorded at the site are presented to demonstrate controller's performance under normal and extreme plant and network operating conditions. © 2012 IEEE.