[en] In 1995 Imatran Voima Ltd started a project for modernization and power upgrading of the Loviisa NPP. This included gradual increase of the reactor thermal power up to 1500 MW (109%) and renovation of the steam turbines. Loviisa NPP Final Safety Analysis Report has been revised in connection with the licensing process of the reactor power upgrading. The project also included certain improvements in the primary and safety systems to ensure plant safety. Trial runs at different power levels up to 109% have been successfully performed during 1997 on both units. The power upgrading has now been completed and a new operating license for 1500 MW power was granted in April 1998 by the Finnish Government. The renovation of the steam turbines will continue up to the year 2000. In this paper, the experience gained in upgrading the power at Loviisa NPP is discussed. The core limitations and the changes in reactor protection system settings are briefly reviewed. Information is provided concerning observed steady state core thermal margins, trial run transient observations and licensing aspects. (Authors)