This is a busbar trunking unit (BTU) designed to prevent the propagation of fire and limit the propagation of heat through building divisions (walls and floors), for a specified time under fire conditions. The role of a busbar insulator extends far beyond simply creating space. It performs two critical, interdependent functions: providing robust electrical insulation and delivering uncompromising mechanical support. The synergy between these two functions is what makes it a linchpin of switchgear. Design of busbars and connections in air insulated substation This chapter focusses on the design implications of connecting or rigid, single or bundled conductors to HV equipment with connectors/clamps, either bolted, welded or compressed. Of importance are equipment and component mechanical and. In electric power distribution, a busbar (also bus bar) is a metallic strip or bar, typically housed inside switchgear, panel boards, and busway enclosures for local high current power distribution, transmission, or switching substations. Their significance arises from their ability to improve efficiency, enhance safety, and streamline overall electrical systems. Koszykowa 75, 00-662 Warsaw, Poland ELKO-BIS Systemy Odgromowe, ul. Internally the trunking may or may not require fire-stop measures according to the.