A high voltage feedthrough assembly comprises an electrical lead extending in a longitudinal direction and an insulative cover capturing the electrical lead and extending along the electrical lead. The high voltage feedthrough assembly also comprises a flange, the insulative cover extending through and being held by the flange, so that the electrical lead extends through the flange. An adapter body has a cavity extending therethrough, is held in a spaced relation to the flange, the width of the cavity being greater than the width of the insulative cover, wherein a portion of the insulative cover and the electrical lead extending from the flange extends into the cavity. A collar is arranged in the adapter body cavity, extending radially between the adapter body and the insulative cover, to hold the insulative cover and electrical lead so that the insulative cover is radially spaced away from the cavity.