Transferred potential [substation earthing]

Any metallic object of significant length may bridge locations that may be at different potential with respect to the general mass of earth. As such, the object may transfer a voltage difference with respect to local earth potential arising from passage of earth fault current to ground or flowing through earthed metallic paths. The metal objects may be fences, pipes cable sheaths and metal conductors, which are referenced to earth or safety earthed at one or more points. A transferred voltage may introduce risk of danger, damage or malfunctioning of equipment. Danger includes electric shock, fire or explosion, damage may be caused by overstressed insulation of equipment and voltages may be a noise to interfere with proper functioning of equipment