elevation out of normal reach. Power neutral busbars may also be insulated because it is not guaranteed that the potential between power neutral and safety grounding is always zero. Earthing (safety grounding) busbars are typically bare and bolted directly onto any metal chassis of their enclosure. They may be enclosed in a metal housing, in the form of a bus duct or busway, segregated-phase bus, or isolated-phase bus. Busbars may be connected to each other and to electrical apparatus by bolting, clamping or welding. Joints between high-current bus sections often have precisely machined matching surfaces that are silver-plated to reduce contact resistance. At extra high voltages (more than 300 kV) in outdoor buses, corona discharge around the connections becomes a source of radio-frequency interference and power loss, so special connection fittings designed for these voltages are used. See also Electrical busbar system Bus (computing) Bus duct Wire bridge Jumper (computing) References Further reading External links Electric power systems components