A discharge apparatus for a wind turbine is disclosed that enables electric charge to be discharged between a first and a second part of the wind turbine that are rotatable relative to each other. The discharge apparatus includes a charge transfer unit electrically connected to the first part, and an electrically conductive slideway electrically connected to the second part. The charge transfer unit includes an electrically insulative sliding member that maintains mechanical contact with the slideway, and a spark-gap electrode electrically connected to the first part and that moves in unison with the sliding member over the slideway. The spark-gap electrode and slideway form a spark gap having a spark-gap width controlled by the sliding member. The first and second parts are electrically isolated from each other in the absence of a spark, and discharge occurs by sparks bridging the spark gap.