Abstract: Xiaoxiang hydropower station excitation system was put into operation in May 2002 with #1 unit run. With the time going, its control performance and stable became worse. In order to keep speed with the power system development tendency and improve economical benefit, the comprehensive transformation scheme to 2 units was carried out, and the results were satisfied. By analysis and comparison of present problems, technical transformation schemes and transformation results, the transformation experience was summarized. The remained problems after excitation system transformation was pointed and relevant advice was presented.

Key words: excitation system, electric power network capacity, voltage rank, technology improvement