The insulator (1) has an electrically insulated disc-shaped support unit (2) with a set of recesses, where each recess accommodates an electrical conductor. Each recess is provided at a position over an outer circumference of the support unit for receiving a clamping unit. The support unit comprises a set of slots on front side that is in close range of outer circumference for receiving a seal ring. An electrically conductive contact unit (10) is inserted into each recess for connecting a phasing conductor. Each contact unit comprises a plug contact (8).