A method for coupling an end of a first insulated conductor to an end of a second insulated conductor that includes placing a sleeve over the end of the first insulated conductor and the end of the second insulated conductor; filling an interior volume of the sleeve with electrically insulating material; and moving the end of the first insulated conductor and the end of the second insulated conductor towards the center of the sleeve. When the ends of the insulated conductors are moved together an end of a core of the first insulated conductor and an end of a core of the second insulated conductor are coupled inside a core coupling located inside the sleeve and the electrically insulating material is compressed between an end portion of an electrical insulator in the first insulated conductor and an end portion of an electrical insulator in the second insulated conductor.