The main focus of this master thesis work was to upgrade ABB’s tap selector type C from 600 to 700 A. The main reason for this was to be able to phase out older models and gain a more cost efficient production. The project initially started with needfinding based from interviews and a literature study, which later evolved into concept generation. In the concept selection phase following external methods were used such as Pugh concept selection and the AHP-process. The work finished with developing the selected concept into a full-scale prototype and testing it according to industry standards. The testing proved that the prototype did not pass the industry standards, but it showed an increase of performance and what components in need of further development in order to finish the upgrade to 700 A.