Detailed design was completed for an existing 500 Hz 11 kV ripple injection plant to be replaced with a new 283 Hz static frequency converter 11 kV ripple injection plant, including replacement of the coupling cells (isolating transformer, tuned reactors and capacitors) and installation of a new 11 kV ring main switch. The detailed design included equipment layout within the existing building, design of equipment primary and secondary connections and SCADA, consolidation of DC supplies and distribution, and determination of the optimum construction procedure to allow the new plant to be commissioned in parallel with the existing plant before the existing plant was removed.