The present disclosure relates to a plug shaft and/or a socket shaft for use in a shaft connection system of a wind turbine. The plug shaft includes a tapered plug end portion for engaging a tapered socket end portion in the shaft connection system. The socket shaft includes a tapered socket end portion for engaging a tapered plug end portion in the shaft connection system. The present disclosure also relates to a shaft connection system of a wind turbine. The shaft connection system includes a first shaft comprising a first tapered end portion and a second shaft comprising a second tapered end portion.