Busbars of a busway system are insulated so as to minimize or eliminate air gaps between busbars. In an embodiment, an insulating sheath is provided with corrugations in regions corresponding to busbar bends. The corrugations allow the sheath to follow the busbar bends without the need to cut or interrupt the sheath. Busbars may therefore be fully insulated without the need for further insulating materials (e.g., tape). Good thermal contact between busbars throughout their length is achieved, improving heat dissipation and efficiency.